COMPARISON BETWEEN THE EFFECTS OF VIP AND THE NOVEL PEPTIDE PACAP ON THE EXOCRINE PANCREATIC-SECRETION OF THE RAT

The effect of intravenous infusion of pituitary adenylate cyclase-acti vating peptide (PACAP) 27, a novel regulatory peptide that shows a clo se structural and chemical similarity to vasoactive intestinal peptide (VIP), on the rat exocrine pancreatic secretion was studied. PACAP an d VIP stimulated the flow rate of exocrine pancreatic secretion (p < 0 .05). However, protein output and amylase secretion were mainly stimul ated by PACAP. Intravenous infusion of VIP increased the plasma levels of secretin (p < 0.05). On the other hand, PACAP released neither sec retin nor VIP. Our results show: (a) both PACAP and VIP stimulate exoc rine pancreatic secretion, (b) PACAP stimulation of pancreatic amylase and protein secretion is greater than that induced by VIP, and (c) PA CAP probably exerts a direct effect on exocrine pancreas whereas some of the actions of VIP might be mediated by secretin.