The effects of acute heat stress on proliferative and apoptotic processes in the rat adrenal cortex

Abstract

Hyperthermia can cause significant structural and functional reorganization of tissues and organs. The prolifera- tive and apoptotic processes of rat adrenal cortex were analyzed by light and electron microscopy after an acute exposure to high ambient temperature. Animals were divided in two groups. The first group consisted of intact controls. The rats from the second group were exposed to a high ambient temperature of 38°C for 60 min. Mitotic chromosomes and the largest number of immunoreactive nuclei for the Ki-67 were observed in the zona reticularis (ZR) of the control animals. The relative number of mitoses after heat stress showed a significant decrease in the zona glomerulosa (ZG; 66.8%), zona fasciculata (ZF; 27.8%) and ZR (86.7%) (for all zones p<0.05), while in the whole adrenal cortex the after-treatment decrease was 61.9% (p<0.05) compared to the controls. Under heat stress numerous apoptotic nuclei were seen at the light and ultrastructural levels in all the zones of the adrenal cortex. Such dynamics of mitosis/apoptosis events seriously affect adrenal cortex morphology.