The effect of pituitary adenylate cyclase activating polypeptide (PACAP) on amylase secretion from guinea pig pancreatic acini.

Pituitary adenylate cyclase activating polypeptide (PACAP) is a novel hypothalamic peptide, structurally related to vasoactive intestinal peptide (VIP). Our previous study in conscious dogs revealed that PACAP stimulated exocrine pancreatic secretion in a manner different from VIP. The objectives of this study were to characterize the effects of PACAP on amylase secretion and intracellular cAMP production in guinea pig pancreatic acini and to compare them with those of VIP and secretin. PACAP38 and PACAP27 (10(-10)-10(-8)M) stimulated amylase secretion from pancreatic acini in a concentration-related manner. The order of potency for amylase secretion was PACAP27 = VIP > PACAP38. The maximally stimulated amylase secretion by PACAP27 was not enhanced by VIP or secretin, but was synergistically increased by cholecystokinin and A23187. PACAP38 and PACAP27 (10(-2)-10(-7)M) increased intracellular cAMP levels in a concentration-related manner. The potency for cAMP production was PACAP38 = PACAP27 = VIP. These results suggest that PACAP38 and PACAP27, like VIP, directly stimulate amylase secretion from guinea pig pancreatic acini through alterations in cellular cAMP levels.