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International Journal of Experimental Pathology logoLink to International Journal of Experimental Pathology
. 2013 Nov 11;94(6):373–386. doi: 10.1111/iep.12050

Progesterone as a morphological regulatory factor of the male and female gerbil prostate

Ricardo A Fochi *, Fernanda C A Santos †, Rejane M Goes ‡, Sebastião R Taboga ‡
PMCID: PMC3944449  PMID: 24205795

Abstract

Testosterone (T) and oestrogen are the main active steroid hormones in the male and female reproductive system respectively. In female rodents progesterone (P4), together with testosterone and oestrogen, has an essential role in the regulation of the oestrous cycle, which influences the prostate physiology through their oscillations. In this work we investigated how the male and female prostate gland of Mongolian gerbils responds to surgical castration at the start of puberty and what are the effects of T, oestradiol (E2) and P4 replacement, using both quantitative and qualitative methods. We also examined the location of the main steroid receptors present in the prostate. In the castrated animals of both sexes an intense glandular regression, along with disorganization of the stromal compartment, and abundant hyperplasia was observed. The replacement of P4 secured a mild recovery of the glandular morphology, inducing the growth of secretory cells and restoring the androgen receptor (AR) cells. The administration of P4 and E2 eliminated epithelial hyperplasia and intensified gland hypertrophy, favouring the emergence of prostatic intraepithelial neoplasia (PIN). In animals treated with T and P4, even though there are some inflammatory foci and other lesions, the prostate gland revealed morphology closer to that of control animals. In summary, through the administration of P4, we could demonstrate that this hormone has anabolic characteristics, promoting hyperplasia and hypertrophy, mainly in the epithelial compartment. When combined with E2 and T, there is an accentuation of glandular hypertrophy that interrupts the development of hyperplasia and ensures the presence of a less dysplastic glandular morphology.

Keywords: castration, gergil prostate, progesterone, puberty

Progesterone (P4) is one of the sex hormones synthesized from pregnenolone, which is considered a key factor of this biochemical pathway, as it can give rise to hormones including testosterone (T) and oestrogen (Lagrange & Kelly 2003; Aron et al. 2004).

In the female body, the ovary is the major P4 secretory site in mammals, which is synthesized recurrently during the reproductive cycle. P4 is an important modulator of normal female reproductive functions, which include ovulation and the glandular development of the uterus and breasts, as well as neurobehavioural expression associated with the sexual responses (Lydon et al. 1995).

All physiological effects of this hormone are regulated by its two isoforms of nuclear receptors, PR and PR-B, which are co-expressed in most target tissues (Graham & Clarke 1997; Mulac-Jericevic & Conneely 2004). The expression of these two receptor isoforms can be modulated by both P4 and oestrogen. In various target tissues, with the exception of the breast, oestrogen has the ability to increase PR expression, while P4 has the opposite effect (Graham & Clarke 1997).

The fact that P4 can be considered a female hormone frequently reduces its importance for the male body. Serum concentrations of P4 in male organism, although comparatively lower than those observed in females, can be considered significant. In rats of both sexes, serum P4 undergoes a significant increase in its levels during the peripubertal period (37–45 days) (Dohler & Wuttke 1974). In the male organism, the synthesis of P4 is performed by the adrenal gland, at levels that may be similar to or greater than the amount produced by the ovaries in females, and also by the Leydig cells in the testicles, through the action of 3β-hydroxysteroid dehydrogenase (3β-HSD) (Fajer et al. 1971; Pelletier et al. 2001; Andersen & Tufik 2006). Besides the presence of the hormone, both isoforms of PR are also expressed in the male reproductive tract, including the prostate gland, whose expression has been studied in prostatic diseases such as benign prostatic hyperplasia (BHP) and carcinomas (Brown et al. 1987; Luetjens et al. 2006; Wang et al. 2007). The use of progesterone derivatives as therapy in men with BHP and prostate carcinoma has been studied for some time (Schacter et al. 1989; Gann et al. 1996). This interest is due to the fact that progesterone is potentially able to inhibit the action of the enzyme 5α-reductase, which is responsible for the conversion of testosterone to dihydrotestosterone (DHT), a metabolite with greater affinity for the androgen receptor (AR) (Frederiksen & Wilson 1971; Cooke et al. 1997).

In the female gonadal system, the presence of a prostatic gland, albeit less studied, has already been documented in both humans and rodents (Zaviacic et al. 2000; Flamini et al. 2002; Santos et al. 2003). Although its function is not fully understood, it is known that the female prostate gland physiology is endocrinologically regulated similar to the male prostate gland (Santos et al. 2008; Biancardi et al. 2010). An important factor to be taken into consideration regarding the female prostate is hormonal fluctuation due to the reproductive cycle. In Mongolian gerbils, structural studies have shown that hormonal changes in T, E2 and P4 during the oestrous cycle promote morphofunctional changes in the female prostate, such as glandular growth during the stages of pro-oestrus and oestrus, and prostatic regression in dioestrus I and II (Fochi et al. 2008).

Another important hormone for prostate homeostasis, and which seems to have an influence on P4, is oestrogen. In addition to prostate physiology regulation through the receptors ERα and ERβ and modulating the action of androgens, studies in male mice have demonstrated that oestrogen is also able to increase the expression of PR in the prostate (Risbridger et al. 2001).

The importance of T and oestrogen for the prostate gland, whether male or female, is widely recognized; however, the interaction between P4 and the prostate is still poorly understood. The presence of both hormone and progesterone receptors in the prostate suggests a physiological role of P4 in the gland. The goal of this work was to analyse the consequences of P4 exogenous administration, as well as its synergism with T and oestrogen, on the structure and physiology of the male and female prostate gland.

Materials and methods

Surgical procedure and experimental groups

In this study, we used both female and male gerbils (Meriones unguiculatus), with ages of 45–104 days. All animals were kept in the biotherium of the Biology Department of the Institute of Biosciences, Letters and Sciences campus of São José do Rio Preto – SP, under adequate light and temperature conditions according to the internal rules of the Committee on Ethics and Animal Welfare (25 °C, 12-h light/12-h dark, with food and water ad libitum).

Initially, the gerbils were arbitrarily divided into two groups: non-castrated and castrated. At 45 days of age, the animals to be castrated were anaesthetized (ketamine 800 μl/Kg and xylazine 200 μl/Kg) and submitted to ovariectomy (females) and bilateral orchiectomy (male) and then returned to the biotherium (Sisk & Meek 2001). When all animals reached 90 days of age, they were divided into five experimental groups for both sexes, with eight animals in each, treated for 14 days every 48 h (Figure 1): normal control (NC), intact animals that received 0.1 ml subcutaneous doses of mineral oil (Nujol; Mantecorp, São Paulo, Brazil); castrated control (CaC), animals that received 0.1 ml subcutaneous doses of mineral oil (Nujol; Mantecorp); castrated + progesterone (CaP), animals that received 0.1 ml of progesterone (Sigma-Aldrich, St. Louis, MO, USA) diluted in mineral oil (0.07 mg/day); castrated + progesterone + oestradiol (CaPE), animals that received 0.1 ml of progesterone (0.07 mg/day; Sigma-Aldrich) + 0.1 ml of oestradiol (β-oestradiol 3-benzoato, 0.07 mg/day; Sigma-Aldrich), diluted in 0.1 ml of mineral oil; castrated + progesterone + testosterone (CaPT), animals that received 0.1 ml of progesterone (0.07 mg/day; Sigma-Aldrich) + 0.1 ml of testosterone (0.07 mg/day; testosterone cypionate – Deposteron/Sigma-Pharma, Hortolãndia, São Paulo, Brazil), diluted in 0.1 ml of mineral oil.

Figure 1.

Figure 1

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Schematic representation of the experimental groups employed in the study. *[NC] = intact animals treated with mineral oil (Nujol®) – 1 mg/kg/every 48 h; *[CaC] = castrated animals treated with mineral oil (Nujol®) – 1 mg/Kg/every 48 h; *[CaP] = castrated animals treated with progesterone (Sigma-Aldrich) – 1 mg/Kg/every 48 h; *[CaPE] = castrated animals treated with progesterone + oestrogen (β-oestradiol 3-benzoato; Sigma-Aldrich) – 1 mg/Kg/every 48 h; *[CaPT] = castrated animals treated with progesterone + testosterone (testosterone cypionate – Deposteron/Sigma-Pharma) – 1 mg/kg/every 48 h.

After 14 days of treatment (48 h after last hormone administration), the gerbils were weighed and killed by decapitation following the inhalation of CO2. The prostates were weighed and processed in accordance with the appropriate methodology for each of the analysis. All animal-handling procedures were carried out during the morning (between 8 and 10:00 a.m.). The treatment time and dosage used were based on the previous work in gerbils and rats, observing the best response period for the hormones administered (Santos et al. 2006; Biancardi et al. 2010; Shinohara et al. 2013).

Serum hormonal dosages

Blood samples were collected through cervical vessel rupture by decapitation, in 4-ml test tubes with separating gel. The serum dosages of progesterone, oestradiol and testosterone were administered according to a published method (Fochi et al. 2008; Santos et al. 2011), in which chemiluminescence was performed in automated Vitros-ECi (Johnson & Johnson, Orthoclinical Diagnostics Division, Rochester, NY, USA), which can detect levels of 0.1–3814 pg/ml for oestradiol, 0.1–150 ng/ml for testosterone and 0.1–100 ng/ml for progesterone. The hormonal ratios were calculated by dividing the dosages values of each animal, in each group individually, and not only by dividing the means obtained for each group.

Structural analysis

The female prostate complex, removed after death, comprises the urethra together with adhered tissues. Although the entire male prostate complex was removed, only the ventral lobe was used with its structural proximity to the female gland, which was weighed separately from the others. The prostatic fragments were fixed by immersion in Karnovsky's solution (5% paraformaldehyde, 2.5% glutaraldehyde in 0.1 m phosphate buffer, pH 7.2) for morphometric and stereological tests and in 4% paraformaldehyde for immunolabelling analyses. After fixation, the tissues were washed under running tap water, dehydrated in an ethanol series, cleared in xylene, embedded in paraffin (Histosec; Merck, Darmstadt, Germany) or glycol methacrylate resin (Historesin embedding kit; Leica, Nussloch, Germany) and cut into 3-μm sections with an automatic rotatory microtome (RM2155; Leica). For the relative weight, the ratio between prostate and body weights was determined (ventral prostate weights/male body weights; female prostate weights/female body weights). The histopathological lesions detected in the gerbil prostate were classified according to the classification system previously described by Shappel et al. (2004), by analysing serial sections submitted to haematoxylin–eosin staining.

Morphometric and stereological analyses

The morphometric and stereological analyses were performed using male and female histological prostate sections, separately, embedded in historesin and stained with haematoxylin–eosin. Prostatic sections were digitized and studied through a System Images Analyzer with Image-Pro Plus 6.0 software (© 1993–2006 Media Cybernetics, Inc., Bethesda, MD, USA). For the morphometric study, measurements of the epithelial cell height and stromal smooth muscle layer thickness were made in 200 random prostatic fields. Through stereology, the relative volumes of prostate tissue compartments (lumen, epithelium, muscular stroma and non-muscular stroma) were obtained using a Weibel multipurpose graticule with 130 points and 60 test lines (Weibel 1963), in a total of 30 prostatic random fields for each group (n = 8).

Immunohistochemistry

To verify the location of steroid receptors in the prostate, immunostaining was performed as follows. Deparaffinized and rehydrated histological sections were subjected to antigen retrieval in Tris–EDTA buffer, pH 9.0, at 100 °C. The endogenous peroxidase blocking was performed with 3% H2O2 in methanol for 15–30 min. The slides were then incubated with primary antibodies to androgen receptor (AR, rabbit polyclonal IgG, N-20; Santa Cruz Biotechnology, Santa Cruz, CA, USA), oestrogen (ERα, rabbit polyclonal IgG, MC-20; Santa Cruz Biotechnology) and progesterone (PR, rabbit polyclonal IgG, C-19; Santa Cruz Biotechnology) at a dilution of 1:100 overnight at 4 °C. After being washed in PBS and incubated in EnVision™ + Dual Link System-HRP (Dako, Carpinteria, CA, USA) polymer for 45 min, the reactions were revealed with diaminobenzidine (DAB), and the sections were counterstained with Harris's haematoxylin. Negative controls were obtained by omitting the step with the primary antibody incubation. The quantification of PR was graded according to Bass et al. (2009), in which intensity ranges from 0 to +3. The +1 score represents fewer than 10% of cells positive for a marker, +2 indicates between 10% and 50% positive and +3 denotes more than 50% positive. For ERα and AR, the total number of cells was counted in 30 microscopic fields randomly selected from each experimental group, which were separated into positively and negatively stained. A minimum of 1000 cells were counted, and then the percentage of immunolabelling was calculated as the number of positive cells divided by the total number of cells. For the final computation of immunostainings, the positive cells of both prostatic compartments (epithelium and stroma) were summed.

Statistical study

All quantitative results are expressed as mean ± SD. The data were initially studied by the analysis of variance (one-way anova) and, subsequently, by Tukey's or Kruskal–Wallis test for multiple comparison, with a 5% significance level (P ≤ 0.05). The statistical tests were performed with Statistica 7.0 software (StarSoft Inc., Tulsa, OK, USA). The quantitative comparisons were carried out only between groups of the same sex.

Results

Biometric analysis

In relation to the body weight of animals, no significant variations were found between all the experimental groups (Table 1). There was, however, in both sexes, a significant weight reduction in the prostate gland and relative weight after surgical castration. None of the treatments were able to recover the weight of the female prostate complex. The ventral lobe of the male gland, however, showed a significant increase in the absolute and relative weight.

Table 1.

Quantitative parameters related to male and female prostate glands (Mean ± SD)

Experimental groups
Parameters Gender NC CaC CaP CaPE CaPT
Body weight (g) Male 67.17 ± 2.64 63.50 ± 5.92 67.17 ± 1.47 67.17 ± 3.37 61.33 ± 7.23
Female 58.80 ± 1.64 56.00 ± 4.24 58.00 ± 3.16 62.40 ± 2.30 56.00 ± 5.83
Prostatic weight (g) Male 0.53 ± 0.09a 0.038 ± 0.008b 0.031 ± 0.004b 0.056 ± 0.009b 0.135 ± 0.015c
Female 0.10 ± 0.05a 0.017 ± 0.006b 0.016 ± 0.002b 0.027 ± 0.005b 0.025 ± 0.004b
Relative weight (g/g) Male 0.008 ± 0.001a 0.0005 ± 0.00003b 0.0004 ± 0.00005b 0.0008 ± 0.0001b 0.0022 ± 0.0002c
Female 0.002 ± 0.0009a 0.0003 ± 0.0001b 0.0003 ± 0.00003b 0.0005 ± 0.0001b 0.0005 ± 0.00006b
Stereology (%)
 Epithelium Male 42.74 ± 2.37a 26.62 ± 0.42b 34.46 ± 1.43c 41.51 ± 2.03a,c 39.23 ± 1.96a,c
Female 27.18 ± 1.51a 27.21 ± 1.34a 27.85 ± 0.97a 35.53 ± 1.83b 39.49 ± 2.03b
 Lumen Male 29.56 ± 3.19a 13.62 ± 1.42b 12.46 ± 2.34b 24.69 ± 2.90c,a 20.08 ± 2.27a,b,c
Female 18.59 ± 2.04a 13.21 ± 1.92b 21.69 ± 1.49a,c 20.56 ± 2.29a,c 20.23 ± 1.40a,c
 Muscular stroma Male 16.97 ± 1.25a 25.534 ± 1.02b 24.43 ± 1.14b 19.41 ± 1.34c,a 24.13 ± 1.47c,b
Female 23.87 ± 1.04a 23.69 ± 1.04a,c 23.69 ± 0.67a,c 21.1 ± 0.94b 25.82 ± 1.19c
 Non-muscular Male 10.72 ± 1.70a 34.23 ± 1.74b 28.64 ± 2.12b 14.38 ± 1.83a 16.56 ± 1.55a
Female 30.36 ± 2.10a 34.26 ± 2.54a 26.77 ± 1.37a,b 23.00 ± 2.23b 23.43 ± 2.67b
Morphometry (μm)
 Epithelium Male 19.6 ± 3.26a 11.79 ± 3.98b 14.62 ± 2.74c 24.86 ± 4.17d 20.28 ± 4.53a
Female 13.92 ± 2.74a 11.91 ± 2.89b 13.75 ± 2.92a 17.49 ± 5.13c 27.14 ± 6.65d
 Muscular stroma Male 14.11 ± 4.79a 9.65 ± 3.17b 10.83 ± 3.84c 17.46 ± 5.49d 15.04 ± 3.68a
Female 11.85 ± 2.90a 11.07 ± 2.28a 13.64 ± 3.14b 18.45 ± 3.68c 14.53 ± 5.09b
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The superscript letters (a,b,c) correspond to the statistical differences between experimental groups (anova and Tukey's tests).

Serological analysis of steroid hormones

Serum concentrations of total T, E2, and P4 are shown in Table 2.

Table 2.

Serum hormone dosage of experimental groups (Mean ± SD)

Groups
Sex Hormones NC CaC CaP CaPE CaPT
Male Testosterone (ng/ml) 2.13 ± 0.287a 0.02 ± 0.002b 0.04 ± 0.005b 0.16 ± 0.018c 8.59 ± 1.352d
Oestradiol (pg/ml) 23.16 ± 4.224a 16.68 ± 3.522a 19.10 ± 4.104a 119.06 ± 31.212b 22.98 ± 2.722a
Progesterone (ng/ml) 0.48 ± 0.094a 0.22 ± 0.041b 9.96 ± 0.512c 11.56 ± 0.461d 2.32 ± 0.530e
Female Testosterone (ng/ml) 0.42 ± 0.192a 0.04 ± 0.020b 0.06 ± 0.063b 0.22 ± 0.091c 7.33 ± 1.661d
Oestradiol (pg/ml) 34.36 ± 7.080a 16.28 ± 2.041b 25.20 ± 4.113a 124.58 ± 18.810c 21.12 ± 3.421a
Progesterone (ng/ml) 6.68 ± 5.093a 0.28 ± 0.110b 15.6 ± 2.930a 20.62 ± 4.830a 1.36 ± 0.462c
Hormonal Ratios NC CaC CaP CaPE CaPT
Male T/E2 103.89 ± 22.912a 1.83 ± 0.567b 1.73 ± 0.328b 1.79 ± 0.435b 417.41 ± 107.480c
T/P4 5.281 ± 1.248a 0.12 ± 0.033b 0.01 ± 0.006c 0.01 ± 0.002c 5.19 ± 1.880a
E2/P4 0.05 ± 0.008a 0.10 ± 0.037a 0.01 ± 0.005b 0.01 ± 0.002b 0.01 ± 0.004b
Female T/E2 14.80 ± 4.394a 2.16 ± 0.570b 4.34 ± 3.084b 1.92 ± 0.329b 569.43 ± 106.542c
T/P4 0.08 ± 0.006a 0.14 ± 0.035a 0.005 ± 0.0003b 0.01 ± 0.006c 5.95 ± 1.161d
E2/P4 0.01 ± 0.003a 0.07 ± 0.024a 0.001 ± 0.0002b 0.008 ± 0.0004b 0.01 ± 0.003b,a
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The superscript letters (a,b,c) correspond to the statistical differences between experimental groups (Kruskal–Wallis test).

Testosterone

A significant reduction due to castration was observed in both sexes of the CaC group, remaining unaltered in the CaP and CaPE animals. The two sexes showed the same pattern for this hormone in the CaPT group, expressing significantly higher levels of testosterone compared with all others.

Oestradiol

In males, the castration did not alter the concentrations of E2, unlike females, in which a significant reduction was observed. The females of CaP and CaPT groups showed the same E2 levels as NC animals. Male animals treated with P4 and P4 plus T did not have altered E2 levels compared with NC and CaC animals. The serum levels of this hormone changed expressively in both sexes of the CaPE group, in which the highest concentration was found in relation to all other groups.

Progesterone

The administration of exogenous P4 triggered a significant increase of this hormone in blood serum. After castration, the P4 levels became lower in the male and female animals. In the CaP group, the P4 concentration increased, reaching values close to those found in male and female animals of the NC group. The highest levels of this hormone were observed in CaPE group of both sexes and were greater than the concentration found in the NC. Gerbils treated with T and P4 revealed no changes in the levels of this hormone, remaining similar to concentrations observed in the NC and CaC groups.

Hormonal ratios

In males, the T/E2 and T/P4 ratios reduced after castration, while only the T/E2 ratio decreased in females. Through treatment, the T/E2 ratio changed only in the CaPT group for both sexes, with a larger ratio than the NC group. In both sexes, administering P4 reduced the T/P4 and E2/P4 ratios, with levels that were the same as the CaPE group. The administration of P4 plus T increased the T/P4 ratio in males and females, but in the former, the E2/P4 ratios also increased, while these values were not altered in females.

Histological quantitative analyses

The morphometric and stereological results are shown in Table 1.

Stereology

In relation to this parameter, there were differences between the sexes. In the males of the CaC, CaP and CaPT groups, there was a significant increase in the volume of the muscle compartment in relation to that observed in the NC. In the CaPE group, the volume of the muscle compartment reduced, becoming similar to that found in the NC. As with epithelium, the castration triggered a significant reduction in the volume of this compartment, which increased in the CaP and CaPT groups. In the CaPE animals, the epithelium presented a more intense development, this compartment being comparable with the NC animals. The lumen showed a volume decrease after castration, increasing in the CaPE and CaPT groups until it reaches normal values. In females, the volume of the muscular compartment remained the same after castration and treatment with P4, while in the CaPE and CaPT groups, the volume decreased. In the CaPE group, the volume of the epithelium increased, remaining the same, however, when compared with CaPT, in which the epithelium reached its highest volume. With castration, there was a reduction in the volume of the luminal compartment; however, it is significantly increased in the CaP, CaPE and CaPT groups.

Morphometry

CaC group

Significant height reductions were observed in the prostatic epithelial cells of males (39.85%) and females (14.44%) compared with intact controls. In ovariectomized females, the muscle layer thickness did not change in relation to the control, unlike males, in which there was a significant reduction in muscle thickness of the castrated animals (30.61%).

CaP group

In the animals of this group, the secretory epithelial cells became larger (24% male; 15.45% female) compared with the CaC. In addition, a significant increase was observed in the smooth muscle layer thickness of both sexes, and in males, the smooth muscle cells were larger than in NC.

CaPE group

In males, the development of the epithelial layer was higher in this group when compared with all of the others, while in females, it was only smaller than in the CaPT group. The muscular layer of this group increased significantly compared with the other groups, in both sexes.

CaPT group

In these animals, differences were observed with regard to the height of the prostatic epithelial cells in relation to gender. In females, the epithelial height was greater than in all other groups. In males, however, this measure was 18.42% lower when compared with the CaPE group. The thickness of the prostatic stromal muscle layer underwent an increase in both sexes. In females, this measure was greater than in the NC and CaC groups, but lower than in the CaPE group and equal to the CaP group. In contrast, the stromal thickness in males of this group was higher than in CaC and CaP groups, but was lower than the CaP and equivalent to NC groups.

Prostate gland structure

CaC group

In both sexes, it was possible to observe common consequences regarding castration. There was an occurrence of several atrophic alveoli with reduced lumen (Figure 2a,b and k,l) containing cell masses inside (Figure 2b,l). These alveoli also had reduced secretory cells, with cuboid or low columnar aspect (2f, g and 2p, q). The epithelium became folded and the basement membrane irregular. The stromal compartment became developed and disorganized, being formed by an irregular smooth muscle layer, concentrically outlining the prostate alveoli (Figure 2g,q and 3a,c). In some alveoli, the muscle cells had an irregular phenotype, which was different from the typically found spindle aspect (Figure 2g,q and 3a, arrow). In both sexes, although the muscle layer became irregular, the thickness reduction was not as evident (Figure 2g,q).

Figure 2.

Figure 2

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Histological sections of the prostatic gland in the different experimental groups, stained with haematoxylin and eosin. Note the greater luminal amplitude of the prostatic alveoli in non-castrated animals (a and k) compared with castrated animals, which have cell bodies within the lumen (b and l). (g and q) Details of prostatic epithelium and stroma showing the atrophy of epithelial cells and also muscle layer disorganization in females with significant reduction in males. Notice the size recovery of the epithelial cells in the prostatic alveoli of progesterone-treated animals (h and r) in relation to castrated animals and the presence of ciliated secretory cells (m). In the CaPE animals, the luminal compartment recovery is evident (d, n), as well as prostatic stroma and epithelium (i and s). In the CaPT group, larger alveoli containing high secretory cells and structured muscle stroma (e, j, o, t) can also be observed. Al: prostatic alveolus; SMC: smooth muscle cell; Ep: epithelium; L: lumen; S: stroma; Arrow: muscular cell with irregular morphology and subepithelial connective stroma; Ur: muscle of urethra. (a–e; k–o: 100× magnification); (f–j; p–t: 1000× magnification).

Figure 3.

Figure 3

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Histological sections of gerbil prostate in CaC, CaP, CaPE and CaPT groups. (a and c): castrated animals; (b, d, e, f, g, h): animals treated with progesterone. It is possible to observe in detail that the folding alveolar epithelium occurred in CaC animals, along with the presence of an irregular basal layer and smooth muscle cells with differentiated phenotype. Progesterone replacement triggers the formation of epithelial detachment and the occurrence of PIN (b, d, e, g). In addition, there is development of ciliated secretory cells (f) and a differentiated phenotype (h). In CaPE animals, cellular debris in the lumen and also frequent PINs (i, j, l) and FH (k) are also observed. In the CaPT group, besides FH, there are inflammatory cells both into the lumen and stroma (m, n, o, p). SMC: smooth muscle cell; Ep: epithelium; L: lumen; S: stroma; PIN: prostatic intraepithelial neoplasia; FH: focal hyperplasia; Arrow: muscular cell with irregular morphology and subepithelial connective stroma; Curved Arrow: ciliated secretory cell; Large Arrow: epithelial folding; Arrowhead: detachment of the epithelium. Double Arrowhead: Secretory cells with a differentiated phenotype; Star: stroma inflammation; *: lumen inflammatory cells.

CaP group

In castrated animals treated with progesterone, the alveoli showed different behaviours for each sex. In males, the luminal compartment underwent few changes, remaining smaller than the NC group (Figure 2c). In females, however, the luminal amplitude was recovered, being similar to prostate alveoli found in intact animals (Figure 2m). For both sexes, progesterone replacement made the secretory cells taller, returning practically to the initial state (Figure 2h,r). In both sexes, a smaller amount of cell masses in the alveoli was observed, although there were instances of cellular debris (Figure 3b and d, arrow head) and intraepithelial neoplasia (Figure 3e,g), characterized by agglomeration of morphologically heterogeneous epithelial cells. The stromal compartment also undergoes significant changes, with recovery of smooth muscle surrounding the prostatic alveoli in both males (Figure 2h) and females (Figure 2r). Initially, there was an increase in muscle thickness in relation to the CaC group, but this was not sufficient to return to the thickness in NC. In females, the muscle layer became thicker and was greater than in the non-castrated group. In the glandular epithelium, it was also possible to find the presence of ciliated secretory cells (Figure 2m and 3f).

CaPE and CaPT groups

CaPE and CaPT were the groups that had major structural changes in the prostate gland. The alveoli showed broader lumens (Figure 2d,n,e,o) and a simple columnar epithelium with large nuclei (Figure 2i,s,j,t). Some foci of abnormal growth in the stromal and epithelial compartments were observed, as scaling of epithelial cells developed into the lumen (Figure 3i,n,o) and there were areas of intraepithelial neoplasia (Figure 3j,k,l,m). In both sexes the secretory cells were significantly larger and the nuclei more spherical than found in the NC group, as well as in the other groups analysed. Relative to the CaPE group, in these cells a greater amount of secretory vesicles was seen in the cytoplasm of the epithelial cells from both sexes (Figure 2i,s). The smooth muscle layer surrounding the prostatic alveoli also became thicker in both sexes, although in males of the CaPE group, the volume of this compartment was reduced by additional treatment with oestrogen. Additionally, in CaPT, it was also possible to observe rearrangement of the stromal and epithelial compartments, with a cellularity that was similar to that observed in the control animals. This change was more intense in male gerbils compared with female ones (Figure 2j). The acini in females of this group, although morphologically similar to control animals, show folded acini arising from the intense cell growth, as well as increased cellularity (Figure 3o). Also in the females of CaPT group, it was possible to observe the occurrence of inflammatory cells inside the luminal compartment (Figure 3p, asterisk) and in the prostatic stroma (Figure 3, star).

Immunohistochemistry

Androgen receptor

The expression of AR-positive cells in the male and female prostate glands showed similar pattern (Table 3). After castration, there was a significant reduction in the amount of AR-positive cells, which were noted as few cells, mainly in the glandular epithelium of the CaC group (Figure 4a,b,f,g). The administration of progesterone (CaP) and progesterone with oestrogen (CaPE) induced recovery of the number of AR-positive cells, reaching the level seen in the NC group. In the CaP group, the presence of labelled cells was more intense in the stroma than in the epithelial layer (Figure 4c,h). With the addition of E2 in the CaPE group, there was a more homogeneous distribution of labelled cells between these two compartments (Figure 4d,i). The amount of AR cells was significantly higher in CaPT when compared with all other studied groups, focusing mainly in the epithelial cells (Figure 4e,j).

Table 3.

Relative frequency values of androgen and oestrogen receptors in the prostate gland (Mean ± SD)

Frequency of AR-positive cells (%) Frequency of ERα-positive cells (%)
Groups Male Female Male Female
NC 33.18 ± 2.32a 38.38 ± 5.68a 4.28 ± 1.30a 1.16 ± 0.48a
CaC 9.65 ± 4.07b 10.00 ± 2.55b 9.16 ± 0.58b,a 7.01 ± 2.28a
CaP 27.45 ± 5.66a 31.77 ± 8.93a 15.82 ± 1.54c 31.49 ± 4.08b
CaPE 28.03 ± 3.25a 35.240 ± 3.3a 18.01 ± 1.70c 23.11 ± 2.06b
CaPT 43.69 ± 2.60c 44.80 ± 2.93c 2.48 ± 0.68a 10.32 ± 1.83a
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The superscript letters (a,b,c) correspond to the statistical differences between experimental groups (anova and Tukey's tests). The superscript letters (a,b,c) correspond to the statistical differences between experimental groups (anova and Tukey's tests).

Figure 4.

Figure 4

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Prostate of adult gerbils submitted to anti-AR immunolabelling. Counterstain: Harris's haematoxylin. It is possible to observe a significant stain decrease in castrated animals, an increase in prostatic stroma of the CaP and CaPE animals and its greater intensity in the prostatic epithelium of the CaPT group. Ep: alveolar epithelium; L: alveolar lumen; S: prostate stroma; Arrow head: positive epithelial cells; Arrow: positive stromal cells.

Oestrogen receptor

ER-positive cells were observed mainly in glandular stroma. In both sexes, castration did not trigger a significant change in the number of ER positive cells (Table 3 and Figure 5a,b,f,g). In females, the exogenous administration of P4 and E2 postcastration led to an increase in ER-positive cells, being higher than in animals of the NC and CaC groups; however, there was no variation between the CaP and CaPE groups (Figure 5h,i). In CaPT animals, the ERα-labelled cells are similar to NC and CaC animals (Figure 5j). In the male prostate gland, more labelled ER cells were seen in CaP and CaPE (Figure 5c,d), but there was a significant reduction in these cells in animals of CaPT, matching the intact gland (Figure 5e).

Figure 5.

Figure 5

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Male and female prostate glands subjected to oestrogen receptor (ERα) immunolabelling. Counterstain: Harris's haematoxylin. There were no ERα-positive cells in glandular epithelium. In the progesterone-treated and CaPE groups, there was an increase in these cells in the prostatic stroma. When progesterone and testosterone were administered together, ERα was decreased in the male prostate, but was not changed in females. Ep: alveolar epithelium; L: alveolar lumen; S: prostate stroma; Arrowhead: stromal positive cells.

Progesterone receptor

There were no labelled cells in prostatic glands of NC and CaC animals (Figure 6a,b,f,g; Table 4). In gerbils treated with progesterone, PR-positive cells were observed mainly in prostatic stroma. In gerbils treated with P4, PR-positive cells exhibited both cytoplasmic and nuclear immunoreaction, and they were found mainly in the prostatic stroma (Figure 6c,h). The PR-labelled cells of the CaPE group were also mostly stromal, with the presence of marked secretory cells for this receptor, especially basal cells (Figure 6d,i). In animals treated with P4 and T, it was still possible to see some PR-positive cells in the stroma; there was, however, a more intense marking in the cytoplasm of the secretory epithelial cells (Figure 6e,j).

Figure 6.

Figure 6

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Histological sections immunolabelled for progesterone receptor (PR). There were no PR-positive cells in the NC and CaC animals. The replacement of progesterone associated with oestrogen triggered the rise of PR-positive cells, mainly in the stroma. In CaPT animals, only a few cells in the stroma and an intense cytoplasmic stain in secretory cells were observed. Insets correspond to male and female negative controls for immunohistochemistry. Ep: alveolar epithelium; L: alveolar lumen; S: prostate stroma; Arrow: positive basal cells; Arrowhead: positive stromal cells.

Table 4.

Semi-quantitative evaluation of progesterone receptor immunohistochemistry among different experimental groups

Intensity of PR-positive cells (%)
Groups Male Female
NC 0 0
CaC 0 0
CaP +2 +2
CaPE +2 +2
CaPT +1 +1
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PR nuclear intensity was graded on a score of 0 to 3+ according to Bass et al.(2009), where (1+) to fewer than 10% of epithelial and stromal PR-positive nuclei, (2+) from 10% to 50% of epithelial and stromal PR-positive nuclei and (3+) to more than 50% epithelial and stromal PR-positive nuclei.

Discussion

This study revealed that the P4, together with E2 and T, causes changes in the prostate morphology, as well as in AR and ERα immunoexpression. The glandular regression of female prostate and male ventral prostate after castration was partially reversed by P4 administration. In addition, the AR- and ERα-positive cells were not changed, resembling the immunolabelling found in intact animals, and PR-positive cells were observed mainly at the prostate stroma. The administration of P4 in conjunction with E2 and T after castration leads to a more intense glandular development in both sexes, as well as an increase in AR- and ERα-labelled cells in female prostates and a rise in AR- and a decrease in ERα-positive cells in the ventral male prostate.

The prostate regression occurs mainly due to the reduction in testosterone serum levels, insofar as the androgens extensively influence their morphophysiology. Studies in which testosterone replacement triggers accelerated processes of glandular development and recovery of prostate morphology confirm its relevance for the gland (Biancardi et al. 2010). However, the development of several kinds of lesions is commonly found in the prostate of testosterone-treated animals (Santos et al. 2006; Scarano et al. 2006; Oliveira et al. 2011). In males, the prostate gland becomes more developed than in females due the greater amount of serum testosterone in the male organism (Thomson 2001; Thomson et al. 2002). Thus, the reduction in its levels probably causes the most intense consequences in the male prostate. These changes found in the epithelial and stromal compartments are expected as, in both sexes, the correct balance of reproductive hormones is key to prostate gland development, differentiation and maintenance (Santos & Taboga 2006; Fochi et al. 2008; Scarano et al. 2008; Oliveira et al. 2011). In both sexes, after castration, the T/E2 ratio decreased mostly due the lower testosterone concentration in the CaC group, reducing the differences among serum levels of these two hormones. The stromal compartment increase was probably due to the deficiency of testosterone, which triggers the rearrangement of extracellular matrix fibres and also the synthesis of others stromal components like collagen. In this scenario, smooth muscle cells may be playing a synthetic role (Vermeulen et al. 2002; Scarano et al. 2008). These findings corroborate studies that demonstrate the importance of balance between the testosterone and oestrogen hormone ratios, as the prevalence of oestradiol can trigger the growth and subsequent neoplastic lesions (King et al. 2006; Prins & Korach 2008).

The replacement of P4, E2 and T in adulthood is not enough to reverse the glandular structure to the normal morphological state observed in the absence of castration. This fact is proved by the evidence of various tissue dysplasias found in several prostatic alveoli of treated animals, such as the presence of a differentiated cellularity. It is important to note that in the group treated with P4 and T, this dysplasia was observed at a lower frequency, especially in males. This is thought to be partly due to the restructuring of the hormonal balance between T and E2, insofar as the imbalance between these two steroids has been identified as one of the main factors responsible for the onset of prostatic lesions. Indeed, the T/E2 ratio of the CaPT animals increased and became larger than the CaC group and even that of the NC.

The development of the muscular stroma observed in the CaP group matches that which occurs in the uterus, in which the P4 hormone is responsible for the gravid endometrium maintenance, inducing the proliferation and differentiation of fibroblasts in the uterine stroma (Punyadeera et al. 2003). Our data demonstrate that P4 administered at a concentration of 1 mg/kg promotes a partial prostate restructuring, besides having moderately anti-androgenic effects in female and male prostate, instead triggers an increase in AR-positive cells. This finding corroborates earlier studies, in which P4 administration at concentrations of 0.3–10 mg was shown to lead to a prostate weight increase in a dose-dependent manner, both in the dorsolateral and ventral lobes (Nishino et al. 2009). The rise in PR-positive cells in the stroma, both in the CaP and CaPE, compared with castrated animals coincided with the increase in ERα cells. This is consistent with previous studies that found that E2 has a stimulatory effect on the PR via ERα (Kurita et al. 2000; Yatkin et al. 2009). The PR is induced by the interaction between ER-linked regions responsive to oestrogen present in its gene, more specifically in the 5′ region (Murakami et al. 1990; Ohta et al. 1993; Parczyk et al. 1997; Kurita et al. 2000). This stimulatory modulation of E2 on PR expression by ER was probably responsible for the hypertrophy and hyperplasia observed in the glands of CaP and CaPE animals. The presence of PR only in the glandular stroma suggests that the growth of secretory cells triggered by P4 is a result of paracrine interaction between the prostatic stroma and epithelium. Therefore, the expression of the PRs in the female prostate does not seem to be inhibited by increased P4 serum concentration. This finding coincides with that which occurs in the uterus during the secretory phase of the menstrual cycle in women (Lessey et al. 1988). Another mechanism that P4 can modulate in the prostate development is the induction of FGF10 and several IGF syntheses, although this cannot be confirmed in this study (Satterfield et al. 2008). The hormonal ratios encountered in the CaP group indicate that in an environment with low T concentrations, such as surgical castration, the increased P4 serum levels, with reduction in T/P4 and E2/P4 ratios, trigger a restructuring process of prostate gland morphology.

In animals treated with progesterone and oestradiol (CaPE group), the hypertrophy observed in prostatic epithelial cells of both sexes demonstrates that progesterone has a key role in glandular homeostasis, ensuring a natural process of epithelial and stromal structuring of prostate together with the androgens and oestrogens. In the CaPE group, the hormone ratios showed the same pattern as that observed in CaP animals. The difference, however, lies in the fact that the CaPE group, besides presenting a significant increase in the levels of E2, also had a higher concentration of T, both hormones with admittedly anabolic effects in the prostate. The increase in lesions and epithelial dysplasia in this group is probably caused by the presence of a high amount of ERα-positive cells, insofar as this type of receptor is responsible for mediating the adverse effects of E2 (McPherson et al. 2008; Ellem & Risbridger 2009). Some papers revealed that E2 has a stimulatory role on the expression of PRs via ERα (Brenner et al. 1990; Ing & Tornesi 1997). On the other hand, in this study, the prostate shows a different behaviour, as, although the PR-labelled cells are superior in the CaPE group compared with NC and CaC animals, we found no differences relative to the CaP animals. Such a finding suggests that the use of P4 and E2 simultaneously diminishes the intensity of PR induction by E2 on the prostate gland. Even though glandular changes were found in the CaPE group, the prostatic epithelium in this group showed lower levels of dysplasia compared with those observed by Scarano et al. (2008) after the administration of E2 alone. Furthermore, the combination of E2 and P4 led to a significant increase in AR cells, a fact that was not observed by Scarano et al. (2008).

The glandular hypertrophy observed in the gerbils of the CaPT group occurred mainly in the epithelial compartment and can be explained by high levels of circulating T found in these animals. Because testosterone is essential for both the development and structural maintenance of the prostate gland, the occurrence of high serum levels of this hormone along with the AR cells increases in this group, which provides a suitable physiological environment for the glandular hypertrophy (Scarano et al. 2006; Prins & Putz 2008). In these animals, the T/E2 ratio increased beyond that observed in control animals. These data indicate that when T levels are higher, independent of the E2/P4 ratio, the prostate grows and develops. The reduction in ERα and PR cells in the male and female prostate of the CaPT group supports the evidence that T has a suppressor effect on this type of receptor (Yatkin et al. 2009). This effect can be added to the least amount of lesions found in this group compared with the others, as the ERα mediates the negative effects of E2.

The reduction in AR-positive cells in the castrated animals corroborates with literature showing that the AR is quite sensitive to serum testosterone variation (Oliveira et al. 2007; Campos et al. 2010; Da Silva et al. 2013). The administration of P4 associated with E2 or T was sufficient to reverse the AR level to the normal state found in the NC, probably because P4 is able to produce androgenic products that can bind to ARs (Nishino et al. 2009). The administration of P4 alone and concomitant with E2, which was employed in this investigation, showed the importance of epithelium–stroma interaction in the prostate gland, as treatment with these hormones improved the AR expression in stromal cells, allowing the recovery of prostate morphology, which was similar to that observed in control animals (Cunha et al. 2002; Cunha 2008). The association between P4 and T proved quite efficient in inducing the expression of AR, proving more intense than in all other studied groups. In addition, in CaPT, the ARs are expressed mainly in the epithelium, in the same pattern as seen in NC animals (Omoto 2008).

The epithelial hypertrophy observed in the gland of both sexes in the CaPT group resembles those studies in which animals were treated only with T, differentiating itself, however, by the presence of less epithelial dysplasia (Scarano et al. 2006; Biancardi et al. 2010; Oliveira et al. 2011). The prostate morphology observed in the CaP and CaPT animals indicates a non-synergistic pattern between the P4 and T. Shinohara et al. (2013) demonstrated that administration of lower doses of P4 is also able to promote, in part, a restructuring of the prostate gland, but their association with T is not sufficient to decrease the installation of glandular lesions. In concentrations of 1 mg/kg, the P4 also appears to compete with the T for the 5α-reductase enzyme; however, the presence of a greater amount of AR in the CaP group, associated with the partial glandular growth, suggests that metabolites resulting from this interaction are able to activate the ARs in the prostate. This feature is enhanced by the CaPT group, as the prostate in this group has become most developed without presenting major injuries; also, this showed an increased expression of AR, indicating a partial blockage of P4 on the inducing action that T has on the gland.

In summary, these results show that physiological interaction between the hormones progesterone, oestrogen and testosterone is essential for the maintenance of the prostate morphophysiology in males and females and that the female prostate has a response pattern that is very similar to the male prostate gland in relation to the main steroid hormones acting in the reproductive system. The fact that the T/E2 ratio did not change, but the E2/P4 ratio decreased and was then developed in the prostatic gland, indicates that P4 is a regulator of prostatic homeostasis. Through the data, it is reasonable to conclude that P4 has a bland anabolic role on both female and male prostate glands. Its interaction with the prostate gland leads to a secretory epithelium hypertrophy and hyperplasia, as well as also influencing the AR and ERα expression patterns. The synergism between P4 and E2 in this work did not influence the expression pattern of PR. On the other hand, in animals treated with T and P4, there was a reduction and also a change in the PR pattern, being expressed mainly in the cytoplasm of secretory cells. Although the prostate morphology of the CaPE and CaPT groups presented similar features to the animals treated separately with T and E2 (Santos et al. 2006; Scarano et al. 2008; Biancardi et al. 2010), there was a decreased incidence of dysplasia in the former groups. This fact is important because it shows that P4 contributes substantially to the morphophysiological balance of the male ventral prostate and female prostate, probably regulating the action of the testosterone and oestradiol on the gland.

Acknowledgments

This article is part of the PhD thesis of RAF from the Institute of Biology, UNICAMP and was supported by grants from the Brazilian Agencies FAPESP – São Paulo Research Foundation (Procs. No. 2008/11386-9) and CNPq – Brazilian National Research and Development Council (Procs. No. 301596/2011-5 research fellowship to S.R.T.). The authors wish to thank Mr. Luiz Roberto Falleiros Júnior for technical assistance, as well as all other researchers at the Microscopy and Microanalysis Laboratory.

References

  1. Andersen ML, Tufik S. Does male sexual behavior require progesterone? Brain Res. Rev. 2006;51:136–143. doi: 10.1016/j.brainresrev.2005.10.005. [DOI] [PubMed] [Google Scholar]
  2. Aron DC, Finding JW, Tyrrell JB. Glucocorticoids and adrenal androgens. In: Greenspan FS, Gardner DG, editors. Basic and Clinical Endocrinology. Stamford, CT: Lange Medical Books; 2004. pp. 362–411. [Google Scholar]
  3. Bass R, Perry B, Langenstroer P, et al. Effects of short-term finasteride on apoptotic factors and androgen receptors in prostate cancer cells. J. Urol. 2009;181:615–619. doi: 10.1016/j.juro.2008.10.029. [DOI] [PubMed] [Google Scholar]
  4. Biancardi MF, Santos FC, Madi-Ravazzi L, et al. Testosterone promotes an anabolic increase in the rat female prostate (Skene's paraurethral gland) which acquires a male ventral prostate phenotype. Anat. Rec. (Hoboken) 2010;293:2163–2175. doi: 10.1002/ar.21250. [DOI] [PubMed] [Google Scholar]
  5. Brenner RM, West NB, McClellan MC. Estrogen and progestin receptors in the reproductive tract of male and female primates. Biol. Reprod. 1990;42:11–19. doi: 10.1095/biolreprod42.1.11. [DOI] [PubMed] [Google Scholar]
  6. Brown T, Clark A, MacLusky N. Regional sex differences in progesterone receptor induction in the rat hypothalamus: effects of various doses of estradiol benzoate. J. Neurosci. 1987;7:2529–2536. [PMC free article] [PubMed] [Google Scholar]
  7. Campos SG, Gonçalves BF, Scarano WR, et al. Tissue changes in senescent gerbil prostate after hormone deprivation leads to acquisition of androgen insensitivity. Int. J. Exp. Pathol. 2010;91:394–407. doi: 10.1111/j.1365-2613.2010.00706.x. [DOI] [PMC free article] [PubMed] [Google Scholar]
  8. Cooke GM, Pothier F, Murphy BD. The effects of progesterone, 4,16-androstadien-3-one and MK-434 on the kinetics of pig testis microsomal testosterone-4-ene-5alpha-reductase activity. J. Steroid Biochem. Mol. Biol. 1997;60:353–359. doi: 10.1016/s0960-0760(96)00223-3. [DOI] [PubMed] [Google Scholar]
  9. Cunha GR. Mesenchymal-epithelial interactions: past, present, and future. Differentiation. 2008;76:578–586. doi: 10.1111/j.1432-0436.2008.00290.x. [DOI] [PubMed] [Google Scholar]
  10. Cunha GR, Hayward SW, Wang YZ. Role of stroma in carcinogenesis of the prostate. Differentiation. 2002;70:473–485. doi: 10.1046/j.1432-0436.2002.700902.x. [DOI] [PubMed] [Google Scholar]
  11. Da Silva DA, Zanatelli M, Shinohara FZ, et al. Effects of exposure to estradiol and estradiol plus testosterone on the mongolian gerbil (Meriones unguiculatus) female prostate. Microsc. Res. Tech. 2013;76:486–495. doi: 10.1002/jemt.22191. [DOI] [PubMed] [Google Scholar]
  12. Dohler K, Wuttke W. Serum LH, FSH, prolactin and progesterone from birth to puberty in female and male rats. Endocrinology. 1974;94:1003–1008. doi: 10.1210/endo-94-4-1003. [DOI] [PubMed] [Google Scholar]
  13. Ellem SJ, Risbridger GP. The dual, opposing roles of estrogen in the prostate. Ann. N. Y. Acad. Sci. 2009;1155:174–186. doi: 10.1111/j.1749-6632.2009.04360.x. [DOI] [PubMed] [Google Scholar]
  14. Fajer AB, Holzbauer M, Newport HM. The contribution of the adrenal gland to the total amount of progesterone produced in the female rat. J. Physiol. 1971;214:115–126. doi: 10.1113/jphysiol.1971.sp009422. [DOI] [PMC free article] [PubMed] [Google Scholar]
  15. Flamini MA, Barbeito CG, Gimeno EJ, Portiansky EL. Morphological characterization of the female prostate (Skene′s gland or paraurethral gland) of Lagostomus maximus maximus. Ann. Anat. 2002;184:341–345. doi: 10.1016/S0940-9602(02)80051-6. [DOI] [PubMed] [Google Scholar]
  16. Fochi RA, Perez AP, Bianchi CV, et al. Hormonal Oscillations During the Estrous Cycle Influence the Morphophysiology of the Gerbil (Meriones unguiculatus) Female Prostate (Skene Paraurethral Glands) Biol. Reprod. 2008;79:1084–1091. doi: 10.1095/biolreprod.108.070540. [DOI] [PubMed] [Google Scholar]
  17. Frederiksen DW, Wilson JD. Partial characterization of the nuclear reduced nicotinamide adenine dinucleotide phosphate: Δ4-3-ketosteroid 5α-oxidoreductase of rat prostate. J. Biol. Chem. 1971;246:2584. [PubMed] [Google Scholar]
  18. Gann PH, Hennekens CH, Ma J, Longcope C, Stampfer MJ. Prospective study of sex hormone levels and risk of prostate cancer. J. Natl Cancer Inst. 1996;88:1118–1126. doi: 10.1093/jnci/88.16.1118. [DOI] [PubMed] [Google Scholar]
  19. Graham JD, Clarke CL. Physiological action of progesterone in target tissues. Endocr. Rev. 1997;18:502–519. doi: 10.1210/edrv.18.4.0308. [DOI] [PubMed] [Google Scholar]
  20. Ing NH, Tornesi MB. Estradiol up-regulates estrogen receptor and progesterone receptor gene expression in specific ovine uterine cells. Biol. Reprod. 1997;56:1205–1215. doi: 10.1095/biolreprod56.5.1205. [DOI] [PubMed] [Google Scholar]
  21. King KJ, Nicholson HD, Assinder SJ. Effect of increasing ratio of estrogen: androgen on proliferation of normal and human prostate stromal and epithelial cells and the malignant cell line LNCaP. Prostate. 2006;66:105–114. doi: 10.1002/pros.20327. [DOI] [PubMed] [Google Scholar]
  22. Kurita T, Lee KJ, Cooke PS, Taylor JA, Lubahn DB, Cunha GR. Paracrine regulation of epithelial progesterone receptor by estradiol in the mouse female reproductive tract. Biol. Reprod. 2000;62:821–830. doi: 10.1093/biolreprod/62.4.821. [DOI] [PubMed] [Google Scholar]
  23. Lagrange AH, Kelly MJ. Neuroactive steroid. In: Henry HL, Norman AN, editors. Encyclopedia of Hormones, vol. 3. Burlington, MA: Elsevier Science; 2003. pp. 8–22. [Google Scholar]
  24. Lessey BA, Killam AP, Metzger DA, Haney AF, Greene GL, McCarty KS., Jr Immunohistochemical analysis of human uterine estrogen and progesterone receptors throughout the menstrual cycle. J. Clin. Endocrinol. Metab. 1988;67:334–340. doi: 10.1210/jcem-67-2-334. [DOI] [PubMed] [Google Scholar]
  25. Luetjens CM, Didolkar A, Kliesch S, et al. Tissue expression of the nuclear progesterone receptor in male non-human primates and men. J. Endocrinol. 2006;189:529–539. doi: 10.1677/joe.1.06348. [DOI] [PubMed] [Google Scholar]
  26. Lydon JP, DeMayo FJ, Funk CR, et al. Mice lacking progesterone receptor exhibit pleiotropic reproductive abnormalities. Genes Dev. 1995;9:2266–2278. doi: 10.1101/gad.9.18.2266. [DOI] [PubMed] [Google Scholar]
  27. McPherson SJ, Ellem SJ, Risbridger GP. Estrogen-regulated development and differentiation of the prostate. Differentiation. 2008;76:660–670. doi: 10.1111/j.1432-0436.2008.00291.x. [DOI] [PubMed] [Google Scholar]
  28. Mulac-Jericevic B, Conneely OM. Reproductive tissue-selective actions of progesterone receptors. Reproduction. 2004;128:139–146. doi: 10.1530/rep.1.00189. [DOI] [PubMed] [Google Scholar]
  29. Murakami R, Shughrue PJ, Stumpf WE, Elger W, Schulze PE. Distribution of progestin-binding cells in estrogen-treated and untreated neonatal mouse uterus and oviduct: autoradiographic study with [125I] progestin. Histochemistry. 1990;94:155–159. doi: 10.1007/BF02440182. [DOI] [PubMed] [Google Scholar]
  30. Nishino T, Ishibashi K, Hirtreiter C, Nishino Y. The prostate growth stimulation by progesterone is due to androgenic products and progesterone receptor-mediated mechanisms. Pharmazie. 2009;64:587–589. [PubMed] [Google Scholar]
  31. Ohta Y, Sato T, Iguchi T. Immunocytochemical localization of progesterone receptor in the reproductive tract of adult female rats. Biol. Reprod. 1993;48:205–213. doi: 10.1095/biolreprod48.1.205. [DOI] [PubMed] [Google Scholar]
  32. Oliveira SM, Leite Vilamaior PS, Corradi LS, Góes RM, Taboga SR. Cellular and extracellular behavior in the gerbil (Meriones unguiculatus) ventral prostate following different types of castration and the consequences of testosterone replacement. Cell Biol. Int. 2007;31:235–245. doi: 10.1016/j.cellbi.2006.10.006. [DOI] [PubMed] [Google Scholar]
  33. Oliveira SM, Santos FCA, Corradi LS, Góes RM, Vilamaior PS, Taboga SR. Microscopic evaluation of proliferative disorders in the gerbil female prostate: evidence of aging and the influence of multiple pregnancies. Micron. 2011;42:712–717. doi: 10.1016/j.micron.2011.03.011. [DOI] [PubMed] [Google Scholar]
  34. Omoto Y. Estrogen receptor-alpha signaling in growth of the ventral prostate: comparison of neonatal growth and postcastration regrowth. Endocrinology. 2008;149:4421–4427. doi: 10.1210/en.2007-1413. [DOI] [PubMed] [Google Scholar]
  35. Parczyk K, Madjno R, Michna H, Nishino Y, Schneider MR. Progesterone receptor repression by estrogens in rat uterine epithelial cells. J. Steroid Biochem. Mol. Biol. 1997;63:309–316. doi: 10.1016/s0960-0760(97)00077-0. [DOI] [PubMed] [Google Scholar]
  36. Pelletier G, Li S, Luu-The V, Tremblay Y, Bélanger A, Labrie F. Immunoelectron microscopic localization of three key steroidogenic enzymes (cytochrome P450scc, 3β-hydroxysteroid dehydrogenase and cytochrome P450c17) in rat adrenal cortex and gonads. J. Endocrinol. 2001;171:373–383. doi: 10.1677/joe.0.1710373. [DOI] [PubMed] [Google Scholar]
  37. Prins GS, Korach KS. The role of estrogens and estrogen receptors in normal prostate growth and disease. Steroids. 2008;73:233–244. doi: 10.1016/j.steroids.2007.10.013. [DOI] [PMC free article] [PubMed] [Google Scholar]
  38. Prins GS, Putz O. Molecular signaling pathways that regulate prostate gland development. Differentiation. 2008;6:641–659. doi: 10.1111/j.1432-0436.2008.00277.x. [DOI] [PMC free article] [PubMed] [Google Scholar]
  39. Punyadeera C, Verbost P, Groothuis P. Oestrogen and progestin responses in human endometrium. J. Steroid Biochem. Mol. Biol. 2003;84:393–410. doi: 10.1016/s0960-0760(03)00061-x. [DOI] [PubMed] [Google Scholar]
  40. Risbridger GP, Wang H, Frydenberg M, Cunha GR. The metaplastic effects of estrogen on mouse prostate epithelium: proliferation of cells with basal cell phenotype. Endocrinology. 2001;142:2443–2450. doi: 10.1210/endo.142.6.8171. [DOI] [PubMed] [Google Scholar]
  41. Santos FCA, Taboga SR. Female prostate: a review about the biological repercussions of this gland in humans and rodents. Anim. Reprod. 2006;3:3–18. [Google Scholar]
  42. Santos FCA, Carvalho HF, Góes RM, Taboga SR. Structure, histochemistry and ultrastructure of the epithelium and stroma in the gerbil (Meriones unguiculatus) female prostate. Tissue Cell. 2003;35:447–457. doi: 10.1016/s0040-8166(03)00071-5. [DOI] [PubMed] [Google Scholar]
  43. Santos FC, Leite RP, Custodio AM, et al. Testosterone stimulates growth and secretory activity of the female prostate in the adult gerbil (Meriones unguiculatus. Biol. Reprod. 2006;75:370–379. doi: 10.1095/biolreprod.106.051789. [DOI] [PubMed] [Google Scholar]
  44. Santos FC, Custodio AM, Campos SG, Vilamaior PS, Góes RM, Taboga SR. Antiestrogen Therapies Affect Tissue Homeostasis of the Gerbil (Meriones unguiculatus) Female Prostate and Ovaries. Biol. Reprod. 2008;79:674–685. doi: 10.1095/biolreprod.108.068759. [DOI] [PubMed] [Google Scholar]
  45. Santos FC, Rochel-Maia SS, Fochi RA, et al. MMP-2 and MMP-9 localization and activity in the female prostate during estrous cycle. Gen. Comp. Endocrinol. 2011;173:419–427. doi: 10.1016/j.ygcen.2011.06.017. [DOI] [PubMed] [Google Scholar]
  46. Satterfield MC, Hayashi K, Song G, Black SG, Bazer FW, Spencer TE. Progesterone regulates FGF10, MET, IGFBP1, and IGFBP3 in the endometrium of the ovine uterus. Biol. Reprod. 2008;79:1226–1236. doi: 10.1095/biolreprod.108.071787. [DOI] [PubMed] [Google Scholar]
  47. Scarano WR, Vilamaior PS, Taboga SR. Tissue evidence of the testosterone role on the abnormal growth and aging effects reversion in the gerbil (Meriones unguiculatus) prostate. Anat. Rec. A Discov. Mol. Cell Evol. Biol. 2006;288:1190–1200. doi: 10.1002/ar.a.20391. [DOI] [PubMed] [Google Scholar]
  48. Scarano WR, de Sousa DE, Campos SG, Corradi LS, Vilamaior PS, Taboga SR. Oestrogen supplementation following castration promotes stromal remodelling and histopathological alterations in the Mongolian gerbil ventral prostate. Int. J. Exp. Pathol. 2008;89:25–37. doi: 10.1111/j.1365-2613.2007.00559.x. [DOI] [PMC free article] [PubMed] [Google Scholar]
  49. Schacter L, Rozencweig M, Canetta R, Kelley S, Nicaise C, Smaldone L. Megestrol acetate: clinical experience. Cancer Treat. Rev. 1989;16:49–63. doi: 10.1016/0305-7372(89)90004-2. [DOI] [PubMed] [Google Scholar]
  50. Shappel SB, Thomas GV, Roberts RL, et al. Prostate pathology of genetically engineered mice: definitions and classification. The consensus report from the Bar Harbor meeting of the Mouse Models of Human Cancer Consortium Prostate Pathology Committee. Cancer Res. 2004;61:2270–2305. doi: 10.1158/0008-5472.can-03-0946. [DOI] [PubMed] [Google Scholar]
  51. Shinohara FZ, Silva DA, Zanatelli M, et al. Progesterone restores the female prostate activity in ovariectomized gerbil and may act as competitor of testosterone in intraprostatic environment. Life Sci. 2013;92:957–966. doi: 10.1016/j.lfs.2013.02.005. [DOI] [PubMed] [Google Scholar]
  52. Sisk CL, Meek LR. Sexual and reproductive behaviors. Curr. Protoc. Neurosci. 2001:8.2.1–8.2.15. doi: 10.1002/0471142301.ns0802s00. [DOI] [PubMed] [Google Scholar]
  53. Thomson AA. Role of androgens and fibroblast growth factors in prostatic development. Reproduction. 2001;121:187–195. doi: 10.1530/rep.0.1210187. [DOI] [PubMed] [Google Scholar]
  54. Thomson AA, Timms BG, Barton L, Cunha GR, Grace OC. The role of smooth muscle in regulating prostatic induction. Development. 2002;129:1905–1912. doi: 10.1242/dev.129.8.1905. [DOI] [PubMed] [Google Scholar]
  55. Vermeulen A, Kaufman JM, Goemaere S, Van Pottelberg I. Estradiol in elderly men. Aging Male. 2002;5:98–102. [PubMed] [Google Scholar]
  56. Wang J, Eltoum IE, Lamartiniere CA. Genistein chemoprevention of prostate cancer in TRAMP mice. J. Carcinog. 2007;6:3. doi: 10.1186/1477-3163-6-3. [DOI] [PMC free article] [PubMed] [Google Scholar]
  57. Weibel ER. Principles and methods for the morphometric study of the lung and others organs. Lab. Invest. 1963;12:131–155. [PubMed] [Google Scholar]
  58. Yatkin E, Bernoulli J, Talvitie EM, Santti R. Inflammation and epithelial alterations in rat prostate: impact of the androgen to oestrogen ratio. Int. J. Androl. 2009;32:399–410. doi: 10.1111/j.1365-2605.2008.00930.x. [DOI] [PubMed] [Google Scholar]
  59. Zaviacic M, Jakubovská V, Belešovic J, Breza J. Ultrastructure of the normal adult human female prostate gland (Skene′s gland) Anat. Embryol. 2000;201:51–61. doi: 10.1007/pl00022920. [DOI] [PubMed] [Google Scholar]

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