Interaction of vasoactive intestinal peptide (VIP) with a mouse adrenal cell line (Y-1): specific binding and biological effects.

Y-1 cells specifically bind radiolabelled vasoactive intestinal peptide (VIP) with a dissociation constant of about 10^?9 M. [¹²⁵I]-VIP bound was not displaced by ACTH. VIP stimulates both steroid and cAMP production, with half-maximal stimulation at 10^?9 and 10^?8 M, respectively. At maximal concentration VIP produces the same stimulation of steroidogenesis as ACTH, but induced three times lower production of cAMP than ACTH. Y-1 DNA synthesis is inhibited by VIP in a dose-dependent manner with half-maximal inhibition at 10^?8 M. At submaximal concentrations the effects of VIP and ACTH on cAMP and steroid production and on inhibition of DNA synthesis are additive. Similar additive effects on cAMP production and on inhibition of DNA synthesis were observed at submaximal ACTH and maximal VIP concentration, but the phenomenon was no longer seen at maximal concentrations of both peptides. These data suggest that in Y-1 cells VIP stimulates, through its own distinct receptors, only a part of the pool of adenylate cyclase sensitive to ACTH.