Action of Secretin and Vasoactive Intestinal Peptide (Vip) on the Adenylate Cyclase System of Pancreatic Acinar Cells

Abstract

The binding of secretin and VIP to the plasma membrane of pancreatic aci nar cells from the rat or the guinea pig results in the activation of aden ylate cyclase which in turn leads to the sécrétion of hydrolases. The N terminal moiety of both hormones has the activation site for adenylate cyclase and is capable of minimal spécifie binding. The Cterminal part contributes to the potency. Two functionally distinct classes of receptors with overlapping affinities for secretin and VIP are présent in guinea pig pancreatic acinar cells, one class with a high affinity for secretin and a low affinity for VIP, and another class with opposite affinities. The effects of secretin and VIP are modulated by a guanyl regulatory site, membranebound glycoproteins and lipids, switching off mechanisms, and the interaction of other gastrointestxnal hormones.