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 mechanisms. In this context paracrine influences between the sympathoadrenal system and the adrenal cortex play an important role. As a prerequisite for these interactions, adrenal medullary cells and cortical cells are highly interwoven as revealed by immunohistochemistry. The potential role of VIP in the regulation of human adrenal steroidogenesis was now investigated in human adrenal cells in primary culture. The primary cultures contained both, cortical and chromaffin cells which were found to be in close cellular contact as revealed by immunocytochemistry. VIP enhanced cortisol secretion from adrenal cells in a dose-dependent manner with a maximal effect at 10(-7) M. VIP stimulated the release of dehydroepiandrosterone (DHEA), testosterone, androstenedione, and aldosterone significantly. The addition of propranolol, a beta-adrenergic antagonist, to the incubation medium attenuated VIP-induced corticosteroid secretion. It is concluded that VIP is a paracrine messenger in the human adrenal that could regulate adrenocortical function at least in part via catecholamines released from the medulla.