Table 1. Experimental research on the effect of microplastic (MP) on the health of laboratory rodents.
| Publication | Animals | Type and size of MP particles, additional treatment | Dose* | Exposure | The results of the impact of MP |
|---|---|---|---|---|---|
| Replacing water in drinkers with MP suspension | |||||
| Luo et al. (2019b) | Pregnant female ICR mice | PS 0.5 and 5 μm | 0.024 and 0.24 mg/kg/day | Throughout the entire pregnancy (3 weeks) | Disorders of fatty acid metabolism were observed in the offspring of mice that consumed MPs. |
| Lu et al. (2018b) | Male ICR mice | PS 0.5 and 50 μm | 0.024 and 0.24 mg/kg/day | 5 weeks | MP causes a decrease in body weight, the relative mass of the liver and adipose tissue; decreased mucin secretion and expression of Muc1 and Klf4 in the colon; significant changes in the composition of the intestinal microflora; disorders of lipid metabolism in the liver. |
| Hou et al. (2021b) | Male ICR mice | PS 5 μm | 0.024, 0.24 and 2.4 mg/kg/day | 5 weeks | Under the influence of MP, there was the decrease in the number of viable spermatozoa in the epididymis, an increase in the proportion of deformed spermatozoa, atrophy and apoptosis of spermatozoa in the testes, an increase in the expression of pro-inflammatory markers: NF-κB, IL-1β, IL-6, a decrease in the expression of the anti-inflammatory molecule Nrf2/HO-1. |
| Jin et al. (2019) | Male ICR mice | PS 5 μm | 0.024 and 0.24 mg/kg/day | 6 weeks | MP accumulates in the intestine, causes a disturbance of the intestinal barrier, changes in the intestinal microflora, disturbances in the metabolism of bile acids. |
| Luo et al. (2019a) | Pregnant female ICR mice | PS 5 μm | 0.024 and 0.24 mg/kg/day | Throughout the pregnancy and lactation (6 weeks) | In the offspring of mice that received MP during gestation and feeding, metabolic disorders in the liver and changes in the composition of the intestinal microflora are detected. |
| Shengchen et al. (2021) | Male C57BL/6 mice | PS 1–10 μm and 50–100 μm | 2.4 mg/kg/day | 8 weeks (On the 25th day, the tibialis anterior muscle was injured by the injection of BaCl2, 30 days after the muscle injury animals were withdrawn from the experiment) | MP consumption led to overproduction of ROS, the development of oxidative stress, and impaired skeletal muscle regeneration. MP suppressed myogenic and stimulated adipogenic differentiation of myosatellite cells. Muscle regeneration was negatively correlated with MP particle size. |
| Zheng et al. (2021) | Male C57 mice | PS 5 μm, induction of acute ulcerative colitis with 3% sodium dextran sulfate (DSS) solution in drinkers | 0.12 mg/kg/day | 7 days | MP exacerbates the DSS-induced acute colitis; causes dystrophic changes in the liver. |
| Deng et al. (2018) | Male CD-1 mice | PS and PE 0.5–1 μm contaminated with organophosphate fire retardants (OPFR) | 0.48 mg/kg/day | 13 weeks | MP and OPFR together exhibited more pronounced effects than either separately: oxidative stress, neurotoxicity, impaired amino acid metabolism and energy metabolism. |
| An et al. (2021) | Female Wistar rats | PS 0.5 μm | 0.06, 0.6 and 6 mg/kg/day | 13 weeks | MP is detected in ovarian granulosa cells, causes their apoptosis and the development of ovarian fibrosis. |
| Hou et al. (2021a) | Female Wistar rats | PS 0.5 μm | 0.015; 0.15 and 1.5 mg/kg/day | 13 weeks | MP is detected in ovarian granulosa cells, causes pyroptosis and apoptosis of these cells. |
| Li et al. (2021) | Female Wistar rats | PS 0.5 μm | 0.06, 0.6 and 6 mg/kg/day | 13 weeks | MP causes damage to the seminiferous tubules, apoptosis of spermatogenic cells, a decrease in sperm motility, an increase in the proportion of abnormal spermatozoa. |
| Li et al. (2020b) | Female Wistar rats | PS 0.5 μm | 0.05, 0.5 and 5 mg/kg/day | 13 weeks | MP causes oxidative stress in the myocardium, apoptosis of cardiomyocytes, cardiosclerosis and cardiac dysfunction. |
| Wei et al. (2021) | Female Wistar rats | PS 500 μm | 0.05, 0.5 and 5 mg/kg/day | 13 weeks | MP consumption leads to disruption of the structure and function of the heart. Damage of mitochondria in cardiomyocytes and death of these cells are noted. Levels of creatine kinase-MB and cardiac troponin I (cTnI) are elevated. |
| Administration of MP suspension through a gastric tube | |||||
| Qiao et al. (2021) | Male C57/B6 mice | PS 0.07 μm (NP) and 5 μm, unmodified, negatively charged carboxylated and positively charged aminated | 0.2 and 2 mg/kg/day | 4 weeks | MP caused intestinal damage, a decrease in the expression of tight contact proteins in the intestinal epithelium, and pronounced changes in the intestinal microflora. |
| Jin et al. (2021) | Male Balb/c mice | PS 0.5 μm, 4 μm and 10 μm | 40 mg/kg/day | 4 weeks | MP particles, 4 and 10 μm in diameter, are detected in the testes one day after the first injection. On the 28th day of exposure, a decrease in testosterone levels and sperm quality is observed. Spermatogenic cells die and are arranged randomly, multinucleated gonocytes appear in the seminiferous tubules. |
| Stock et al. (2019) | Male genetically modified C57BL/6 mice | PS 1 μm, 4 μm and 10 μm | 1, 63 and 33 mg/kg/day according to size | 4 weeks | In animals getting MP, body and organ weight did not change, there were no signs of oxidative stress or inflammation in the intestine. |
| Wang et al. (2021) | Male C57BL/6 mice | PS 2 μm | 8 and 16 mg/kg twice a week | 4 or 8 weeks | MP accumulates in the kidneys, causing structural damage. In the kidney, levels of ER stress, the production of inflammatory markers and proteins associated with autophagy are increased. |
| Sun et al. (2021) | Male C57BL/6 mice | PS 5 μm | 4 and 20 mg/kg/day | 4 weeks | MP affects hematopoiesis. Decreases the number of leukocytes and the CFU-GM, CFU-M, CFU-G; changes 41 (lower dose) or 32 (large dose) genes in bone marrow cells. |
| Deng et al. (2017) | Male ICR mice | PS 5 and 20 μm | 4 mg/kg/day | 4 weeks | The maximum concentration of MP in the liver, kidneys, and intestines is reached by the 14th day of the experiment. The relative weight of the liver decreases at a MP dose of 0.5 mg/day. In the liver, inflammatory changes and fatty degeneration are observed. Disorders of energy and lipid metabolism, oxidative stress were revealed. |
| Yang et al. (2019) | Male mice | PS 5 and 20 μm | 0.4, 4 and 20 mg/kg/day | 4 weeks | Toxicokinetic/toxicodynamic study of MP influence. The accumulation of MPs in the liver, kidneys, and intestines was assessed over time. |
| Xie et al. (2020) | Male Balb/c mice | PS 5–5.9 μm | 0.4; 4 and 40 mg/kg/day | 6 weeks | MP causes a decrease in spermatozoa number and mobility, an increase in the proportion of deformed spermatozoa; a decrease in the activity of the enzymes succinate dehydrogenase and lactate dehydrogenase; decrease in testosterone content, development of oxidative stress. |
| Rafiee et al. (2018) | Male Wistar rats | PS 0.025 and 0.05 μm (NP) | 1, 3, 6 or 10 mg/kg/day | 5 weeks | In neurobehavioral tests, statistically significant changes were not observed upon exposure to MP, body weight did not change. |
| da Costa Araújo & Malafaia (2021) | Male Swiss mice | PE 35.46 ± 18.17 μm | 4.8 mg/kg/day | 1 week | In animals that consumed MP, a decrease in locomotor activity and a higher anxiety index in the open field test, a lack of protective social aggregation, and behavior with a reduced risk assessment when meeting a potential predator were observed. |
| Park et al. (2020) | Male and female ICR mice | PE 40–48 μm modified with acid and hydroxy groups | 3.75, 15 and 60 mg/kg/day | 13 weeks | MP caused reactions from the immune system in adult animals: in mice of both sexes, the content of neutrophils in blood increased, in females, the content of IgA in blood increased, and the subpopulation composition of lymphocytes in the spleen changed. In animals receiving MP, the number of live births per female and the body weight of newborn pups decreased significantly. |
| Deng et al. (2021) | Male CD-1 mice | PE 0.4–5 μm, phthalate-contaminated | 100 mg/kg/day | 4 weeks | MP can penetrate the testes of mice. MPs with phthalates accumulate in the liver, intestines, and testes. MP enhances the reproductive toxicity of phthalates. |
| Deng et al. (2020) | Male CD-1 mice | PE 45–53 μm, phthalate-contaminated | 100 mg/kg/day | 4 weeks | MP can transport and release phthalates into the intestines of mice. MP enhances the toxic effects of phthalates: increased intestinal permeability, oxidative stress, inflammatory reactions, metabolic disorders. |
| MP in food | |||||
| Li et al. (2020a) | Male C57BL/6 mice | PE 10–150 μm | 0.24, 2.4 and 24 mg/kg/day | 5 weeks | MP caused changes in the composition and diversity of intestinal microflora, an increase in the level of IL-1α in the blood serum, an increase in the proportion of Th17 and Treg cells among CD4+ cells. MP in a high dose caused the development of inflammation in the small intestine. |
| Intratracheal introduction of MP | |||||
| Fournier et al. (2020) | Pregnant female Sprague Dawley rats | PS 0.02 μm (NP) | 2.64 × 1014 MP particles | 1 time on day 19 of gestation, removal from the experiment in a day | MP particles were detected in maternal lungs, heart and spleen. MP was detected in the placenta, as well as in the liver, lungs, heart, kidneys and brain of fetuses, which indicates translocation of MPs from the mother’s lungs to the fetal tissue in late pregnancy. |
| MP inhalation | |||||
| Lim et al. (2021) | Male and female Sprague-Dawley rats | PS 0.1 μm (NP) | MP air concentration 0.75 × 105, 1.5 × 105 and 3 × 105 particles/sm3 | 2 weeks | Under the influence of MP, the increase in the relative mass of the heart, a decrease in the content of leukocytes and lymphocytes in the blood, a decrease in the time of inspiration were revealed, furthermore a tendency to an increase in the content of cytokines TGF-β and TNF-α in the lung tissue was observed. |
| Intraperitoneal injection of MP | |||||
| Estrela et al. (2021) | Male Swiss mice | PS 0.023 μm (NP) | 14.6 ng/kg | 3 days | MP causes cognitive impairments, violations of the redox balance, and a decrease in the activity of acetylcholinesterase in the brain. |
Notes:
*
In articles, when MP is added to drinkers, as a rule, the concentration of MP in drinkers is indicated as mg/l, when administered through a gastric tube - the amount of MP (mg) per animal. We recalculated the MP dose as mg of MP per kg of animal’s weight per day, taking the average weight of a mouse equal to 25 g, a rat - 250 g, daily water consumption in a mouse - 6 ml, in a rat - 25 ml.
NP – nanoplastic.