Objective To study a local effect of pituitary adenylate cyclase activating polypeptide (PACAP1-27) on glucose-evoked insulin release under in vivo conditions.
Intervention Glucose and PACAP1-27 were locally infused to the pancreas via the superior pancreaticoduodenal artery without interrupting the blood supply.
Main outcome measures Plasma insulin and glucose concentrations were determined in samples obtained from the superior pancreaticoduodenal vein and the aorta. Superior pancreaticoduodenal venous blood flow was measured to compute the net output of insulin.
Results PACAP1-27 (0.005-5 µg) increased the basal insulin secretion by about 15 folds in a dose-dependent manner. Local infusion of either glucose (5%) or PACAP1-27 (0.05 µg) resulted in a significant increase in the basal insulin output to about 300 µU·min-1g-1, which was highly reproducible upon the second administration of the same dose with an interval of 30 min. When PACAP1-27 was simultaneously given during glucose infusion, the increased insulin output due to glucose was further enhanced to about 600 µU·min-1g-1. The net increase in PACAP1-27-induced insulin output in the presence of glucose was significantly greater than that obtained with PACAP1-27 alone. There exists a strong and highly significant correlation between changes in glucose level and those in insulin output when both glucose and PACAP1-27 were administered simultaneously.
Conclusion The results indicate that PACAP1-27 directly enhances the glucose-evoked insulin secretion in the endocrine pancreas in anesthetized dogs. The study suggests that PACAP may play a local facilitating role in insulin secretion in response to glucose loading.