Pituitary adenylate cyclase activating polypeptide (PACAP) redistributes the blood within the pancreas of...

The aim of the study was to evaluate the effects of pituitary adenylate cyclase activating polypeptide-38 (PACAP-38) on splanchnic blood flow in anesthetized rats. For this purpose, either PACAP-38 dissolved in saline or saline alone was injected intravenously 5 (10 nmol/kg body weight (bw) PACAP-38) and 30 min (5 or 10 nmol/kg) before measurements. The blood flow to the whole pancreas, islets, duodenum and colon was then measured with a microsphere technique. The higher dose of PACAP-38 slightly increased blood glucose concentrations at both 5 and 30 min after administration, whereas the lower had no effect. Both doses of PACAP-38 induced a transient initial decrease in mean arterial blood pressure. The lower dose of PACAP-38 decreased fractional islet blood flow 30 min after administration, but did not affect the other blood flows. The higher dose of the peptide (10 nmol/kg bw) caused an increase in whole pancreatic blood flow at both 5 and 30 min after administration, whereas islet blood flow was only increased at the former time. At both time points PACAP-38 redistributed the blood flow within the pancreas in favour of the exocrine pancreas. This resulted in a decreased fractional islet blood flow, i.e., the fraction of whole pancreatic blood flow diverted through the islets. At 5 min after PACAP-38 administration duodenal blood flow was decreased, whereas after 30 min no effects on duodenal or colonic blood flow were observed. Administration of a VIP antagonist intravenously (20 nmol/kg bw) decreased the PACAP-38-induced pancreatic blood flow increase and intrapancreatic redistribution. When only the VIP antagonist was given both pancreatic and islet blood decreased in concert. It is concluded that administration of PACAP-38 induces a blood flow increase in the pancreas, preferably in the exocrine parts of the gland, by actions mediated by PACAP-38 receptors shared with VIP.