Effect of truncal vagotomy on pancreatic polypeptide response after intravenous glucose administration

Intravenous glucose infusion was performed in six dogs with and without truncal vagotomy, and plasma pancreatic polypeptide (PP) responses were compared before and after truncal vagotomy. Following truncal vagotomy, basal PP levels decreased significantly from 286 +/- 64 pg/ml (mean +/- S.E.) to 94 +/- 14 pg/ml (P less than 0.05). Basal plasma insulin and blood glucose levels also tended to be lower, but not significantly. During the infusion of glucose, blood glucose concentrations rose rapidly in both groups and after 15 min reached peak values which were not significantly different from each other. In the vagotomized group the plasma insulin response to intravenous glucose infusion was significantly lower than in the control group. Following intravenous glucose loading, plasma PP concentrations decreased rapidly in both groups, but the PP level in the vagotomized group was suppressed only to 77 +/- 4% of the basal level whereas in the control group it decreased by 45 +/- 8%, significantly lower than in the vagotomized group (P less than 0.01). These results suggest that basal PP is regulated by vagal tonus and that vagus controls, at least in part, suppression by intravenous glucose administration.