Immunohistomorphometric response of pituitary growth hormone-producing cells in rats to prolonged exposure to moderately elevated ambient temperature

Introduction/Objective. The main objective of this study was to investigate the effect of prolonged exposure (4, 7, 14, 21, 60 days) of rats to moderately high ambient temperature (35 ? 1?C) on the immunohistomorphometric parameters of pituitary somatotrophic (GH) cells. Methods. The experiment was conducted on 42 adult Wistar rats, equally divided into six experimental groups (n = 7). Five were continuously exposed to a temperature of 35 ? 1?C, while the control group was kept at 20 ? 2?C. GH cells were visualized using the peroxidase?antiperoxidase immunohistochemical method. The morphometric analysis was conducted using the M42 multipurpose test system. Results. Rats from all experimental groups had significantly (p < 0.05) reduced body mass compared with the control. After four and 14 days of exposure to moderate heat, the absolute pituitary weight was significantly (p < 0.05) increased by 23.1% and 27.7%, respectively, in comparison with the control. GH cells in all groups were oval and located near capillaries with numerous dark granules. Morphometric analysis of cellular and nuclear volumes of GH cells in the experimental group significantly decreased (p < 0.05) compared with the control group. Conclusion. It can be concluded that chronic exposure of adult male rats to moderately high ambient temperatures reduced the immunohistomorphometric parameters of GH cells.