Acute stress effects on the adrenal cortex in the rat. A biochemical and immunohistochemical study.

Activation of the stress system induces physiologic alterations as well as behavioural ones that ultimately improve the adaptability of the organism to adverse conditions. In our previous study on the morpho-functional evolution of the adrenal cortex, from birth to adulthood, the question of what could be the contribution of immobilization stress to the observed hormonal levels was brought up. Male adult rats were submitted to immobilization of variable duration. The antibody IZAb was used to allow a correct differentiation between the zona glomerulosa (ZG) and the inner zones of the cortex (IZ). A significant increase of the ACTH levels, especially at 5 and 30 min was observed. Corticosterone (B), surprisingly, revealed 2 peaks of secretion: one at 30 sec and another at 30 min. The area of the cortex, determined by an image analyser, only showed a slight decrease at 30 sec. The proportions of the cortical area occupied by ZG and IZ were unaltered. We concluded that a corticosterone peak at 30 sec precedes the elevation of ACTH induced by stress. Only the second peak, in view of its parallel course to ACTH, can be attributed to an effect of this pituitary hormone.