CELLULAR COMMUNICATION IN THE NEUROADRENOCORTICAL AXIS - ROLE OF VASOACTIVE INTESTINAL POLYPEPTIDE (VIP)

It is well established now that adrenocortical function, besides being regulated through systemic factors, is influenced by intra-adrenal me chanisms. In this context paracrine influences between the sympathoadr enal system and the adrenal cortex play an important role. As a prereq uisite for these interactions, adrenal medullary cells and cortical ce lls are highly interwoven as revealed by immunohistochemistry. The pot ential role of VIP in the regulation of human adrenal steroidogenesis was now investigated in human adrenal cells in primary culture. The pr imary cultures contained both, cortical and chromaffin cells which wer e found to be in close cellular contact as revealed by immunocytochemi stry. VIP enhanced cortisol secretion from adrenal cells in a dose-dep endent manner with a maximal effect at 10(-7) M. VIP stimulated the re lease of dehydroepiandrosterone (DHEA), testosterone, androstenedione, and aldosterone significantly. The addition of propranolol, a beta-ad renergic antagonist, to the incubation medium attenuated VIP-induced c orticosteroid secretion. It is concluded that VIP is a paracrine messe nger in the human adrenal that could regulate adrenocortical function at least in part via catecholamines released from the medulla.