Table 2.
Effects of brief and repeated noise exposure on the numerical density and distribution of catecholamine granules in the adrenaline (A) and noradrenaline (NA) cells of the adrenal medulla
| A cells | NA cells | |||||||
|---|---|---|---|---|---|---|---|---|
| Control | Brief noise | Control | Repeated noise | Control | Brief noise | Control | Repeated noise | |
| Number CA granules per µm2cytoplasm | 3.1 ± 0.2 | 4.4 ± 0.1* | 3.2 ± 0.1 | 2.2 ± 0.1* | 3.3 ± 0.2 | 4.1 ± 0.1* | 3.4 ± 0.2 | 3.8 ± 0.1* |
| Perinuclear granules (PN%) | 42 ± 3 | 42 ± 3 | 43 ± 3 | 39 ± 4 | 41 ± 4 | 38 ± 2 | 42 ± 4 | 43 ± 4 |
| Perimembrane granules (PM%) | 58 ± 3 | 58 ± 3 | 58 ± 3 | 61 ± 6 | 59 ± 3 | 61 ± 3 | 58 ± 3 | 57 ± 5 |
| Polarization index (PM/PN) | 1.4 ± 0.1 | 1.4 ± 0.1 | 1.3 ± 0.1 | 1.6 ± 0.1* | 1.4 ± 0.1 | 1.6 ± 0.1* | 1.4 ± 0.1 | 1.3 ± 0.1 |
Percentage of granules situated in the perinuclear (PN) and perimembrane (PM) position in baseline conditions (controls) or after different amounts (brief or repeated) of noise exposure in A or NA cells of the adrenal medulla. Perinuclear and PM areas were defined as rectangles with the long side opposite either the nuclear or the plasma membrane, respectively (see methods). The polarization Index is an integrated number indicating intracellular granule distribution. It is calculated by the ratio between the amount of CA granules located in the PM position and the amount of granules in the PN position (PI = PM/PN). Even in baseline conditions (controls) there is a physiological polarization of CA granules towards the plasma membrane, which is similar for NA and A cells. However, there is a different response between A and NA cells after noise exposure. While brief noise exposure increases the polarization of NA granules only, prolonged noise exposure results in opposite effects leading to increased polarization of A granules. Values indicating granule number represent the mean ± SEM obtained from 100 counts of 10 animals per group. Values for PM and PN are expressed as the percentage of the mean ± SEM percentage of 10 animals per group. Values for PI represent the ratio between the mean PM and PN ± SEM obtained from 100 counts of 10 animals per group. Comparisons between groups have been carried out using anovawith Sheffe's post hoc analysis.
P< 0.05 compared with controls.