Vasoactive intestinal peptide is a local regulator of adrenocortical function

Several immunohistochemical studies have shown that vasoactive intestinal peptide (VIP) is present in nerve terminals supplying the adrenal capsule and zona glomerulosa, but its function in this tissue has been unclear. Using the intact perfused rat adrenal preparation we showed that VIP is a vasodilator in this tissue, and stimulates aldosterone and corticosterone secretion. The effects of VIP are dependent on the tissue preparation used, and we have evidence that the effect on aldosterone secretion is secondary to local catecholamine release. Administration of a low sodium diet greatly enhanced the aldosterone response to VIP stimulation. Receptor binding studies reveal an increase in the number of VIP receptors in zona glomerulosa tissue in the low sodium group. We have also investigated the regulation of adrenal tissue content of VIP. The low sodium diet caused an increase in peptide content, while a high sodium diet had the opposite effect. Splanchnic nerve section, on the other hand, had no effect on zona glomerulosa VIP content. These findings suggest that adrenal VIP has a significant role in the regulation of zona glomerulosa function, particularly in response to altered electrolyte balance.