Affiliation:
1. University of Niš , Faculty of Medicine, Department of Anatomy , Niš , Serbia
2. University of Belgrade , Institute for Biological Research “Siniša Stanković” – National Institute of Republic of Serbia , Department of Cytology , Despot Stefan Blvd. 142 , Belgrade , Serbia
3. Ss. Cyril and Methodius University in Skopje , Institute of Reproduction and Biomedicine , Faculty of Veterinary Medicine-Skopje, Department of Functional Morphology , Lazar Pop-Trajkov 5-7 , Skopje , Republic of North Macedonia
Abstract
Abstract
Global warming causes an increased ambient temperature and prolonged heatwaves during the summer, which represent stressogenic factors affecting the hypothalamo-pituitary-adrenocortical (HPA) axis in mammals. The aim of this study was to investigate the effects of long-term (7-60 days) exposure to moderately elevated ambient temperature (35 ± 1°C) on the histological aspect and secretory ability of pituitary adrenocorticotropic (ACTH) cells, as well as on the corticosterone output, in adult rats. Stereological parameters of ACTH cells were estimated upon immunohistochemistry. The blood concentrations of ACTH and corticosterone were determined by immunoassays. The volume of ACTH cells in rats exposed to moderately high temperature for 7, 14, 21, 30 and 60 days decreased (p<0.05) by 18.1%, 14.5%, 13.5%, 8.6% and 14.2% respectively, compared to the same parameter in the controls. The volume density of ACTH cells in the groups exposed to elevated temperature for 7, 14, 21, 30 and 60 days decreased (p<0.05) by 40.0%, 33.3%, 26.7%, 13.3% and 26.7% respectively, in comparison with control rats. The plasma concentration of ACTH varied differently (p<0.05) with the duration of exposure to the elevated temperature. The serum concentration of corticosterone was decreased (p<0.05) by 54.9%, 24.4%, 29.9%, 21.1% and 24.4% in groups subjected to moderately high temperature for 7, 14, 21, 30 and 60 days respectively, all compared to the control value. Despite some signs of functional recovery of ACTH cells during the treatment, the impression is that the long-term character of this stressor overcomes the capacity of the HPA axis for resistance.
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