Endocrine Abstracts

The global warming and its impact on the summer average temperature elevation, in the south-eastern parts of Europe, represent an inevitable stress for living organisms in this region. Heat stress was shown to be the strongest one, when compared to immobilization or cold stress. Activation of the hypothalamo-pituitary–adrenal (HPA) axis during exposure to various types of stressors is well-known physiological concept. The effect of 24 h exposure to heat stress on the morphology of pituitary adrenocorticotropes (ACTH cells) and adrenal cortex, especially on zona fasciculata (ZF), in adult male Wistar rats, was examined. The experimental animals (n=7) were exposed for 24 h to high ambient temperature (35±1 °C). The control group (n=7) was kept at room temperature (20±2 °C). The pituitary and left adrenal glands were fixed in Bouin’s solution and serially cut (5 μm). The ACTH cells were identified by the peroxidase-antiperoxidase (PAP) immunohistochemical procedure, while the cells of adrenal cortex were stained with hematoxylin–eosin. The volume of ACTH- and ZF- cells and their nuclei were estimated using the multiporpose test system M₄₂. The body weight in heat stressed rats was decreased (P<0.05) by 15.3%, compared to the controls. The relative pituitary weight was significantly increased (P<0.05) by 16.5%, in comparison with the corresponding control. The ACTH cell volume, as well as the volume density, were significantly decreased (P<0.05) by 12.3 and 26.7% respectively, in comparison with the controls. Absolute volumes of the adrenal gland, adrenal cortex, ZF, as well as the ZF cells were also decreased (P<0.05) by 10.7, 8.6, 15.2 and 3.3% respectively, compared to the controls. These findings suggest that one day exposure of adult male rats to high ambient temperature (35±1 °C) has the inhibitory effect on the morphological characteristics of ACTH- and ZF-cells in adult male rats.