Stimulatory effect of vasoactive intestinal peptide (VIP) on the secretory activity of dispersed rat adrenocortical cells. Evidence for the interaction of VIP with ACTH receptors

VIP dose-dependently increased basal, but not submaximally ACTH (10 −10 M)-stimulated, aldosterone (ALDO) and corticosterone (B) secretion of dispersed rat capsular and inner adrenocortical cells, respectively. The maximal stimulatory effect (60–70% rise) was obtained with a VIP concentration of 10 −8 M. [4-Cl-D-Phe 6 ,Leu 17 ]-VIP, a VIP-receptor antagonist (VIP-A), and corticotropin inhibiting peptide (CIP), an ACTH receptor antagonist (both 10 −6 M), completely annulled VIP (10 −8 M)-evoked rises in basal ALDO and corticosterone secretions. The ACTH (10 −10 M)-enhanced (about 5-fold) production of both hormones was completely reversed by CIP (10 −6 M) and only partially reduced (about −30%) by VIP-A (10 −6 M). The hypothesis is advanced that the weak secretagogue effect of VIP on dispersed rat capsular and inner adrenocortical cells may be due to its positive interaction with ACTH receptors.