EFFECT OF PITUITARY ADENYLATE CYCLASE-ACTIVATING POLYPEPTIDE ON EXOCRINE AND ENDOCRINE SECRETION IN THE OVINE PANCREAS

The role of pituitary adenylate cyclase-activating polypeptide (PACAP) in the regulation of exocrine and endocrine pancreas was investigated in conscious sheep. Intravenous infusions of PACAP-27 and PACAP-38 (1 , 3, and 10 pmol/kg/min) for 10 min during phase II of the duodenal mi grating myoelectric complex accelerated pancreatic protein and amylase outputs dose-dependently. The responses in enzyme secretion to both P ACAPs at the highest doses were inhibited significantly by atropine in fusion (14.4 nmol/kg/min). Vasoactive intestinal polypeptide (VIP) at 3 pmol/kg/min significantly accelerated protein but not amylase output s, although the response to the highest dose was not significantly inf luenced by atropine. PACAP-27 and VIP increased pancreatic juice flow and bicarbonate output dose-dependently; however, the responses to the highest dose were not altered significantly by atropine. On the other hand, intravenous injection of PACAP-38 (100 pmol/kg) did not influen ce basal plasma concentration of insulin, glucagon, and glucose. Moreo ver, PACAP 38 (1-100 pmol/kg) altered neither pancreatic endocrine res ponse to intravenous infusion of glucose (20 mu mol/kg/min) not that t o n-butyric acid (33 mu mol/kg/min). These results suggest that PACAP contributes to the regulation of exocrine secretion of the ovine pancr eas but not to endocrine secretion. PACAP appears to accelerate pancre atic enzyme secretion mostly via the cholinergic nerves. Copyright (C) 1996 Elsevier Science Inc.