Role of the vasoactive intestinal peptide in a neuroendocrine regulation of the adrenal cortex.

Using a method for isolation and perfusion of pig adrenal glands with preserved nerve supply, we measured the release of cortisol and aldosterone and of the vasoactive intestinal peptide (VIP) after electrical stimulation of the splanchnic nerves. Additionally, the effect of VIP (at final concentrations of 10(-10)-10(-7) M) in the perfusion medium on the release of cortisol and aldosterone was investigated. The amount of VIP contained within the adrenal was measured by chromatography, and the localization of VIP in the adrenal gland was investigated immunohistochemically. Stimulation of the splanchnic nerves provoked a significant release of VIP (2.7- to 17-fold) and of the corticosteroids cortisol (2.5- to 6.7-fold) and aldosterone (1.6- to 2.8-fold). VIP added to the perfusion medium stimulated secretion of both corticosteroids with a maximal effect at 10(-8) M. Cortisol release increased 20- to 58.5-fold over basal, aldosterone release increased 2.9- to 4.9-fold over basal. This VIP-stimulated release had the same range of magnitude as the release stimulated by adrenocorticotropic hormone in physiological concentrations (10(-10) M). The mean concentration of VIP-like immunoreactivity in the adrenal glands was 8.9 +/- 2.1 pmol/g wet weight. Immunohistochemical investigations showed immunoreactive cells within the adrenal medulla as well as VIP-ergic nerve fibers in the cortex of the adrenal gland. These data show that the adrenal cortex can be stimulated independent of the hypothalamus-pituitary-adrenal axis via a neuroadrenocortical axis. In this regulatory pathway, the VIP-ergic innervation of the adrenal cortex may be a potent stimulatory element.