Effect of pancreatic polypeptide on gallbladder filling

Recent studies suggest that pancreatic polypeptide (PP) alters gallbladder pressure and reduces delivery of bile to the duodenum. Whether this peptide influences gallbladder emptying and/or filling is not clear. Using the prairie dog model, we tested the hypothesis that exogenous PP induces gallbladder filling. Animals maintained on control diets underwent laparotomy with placement of catheters into the gallbladder and common bile duct. The gallbladder was perfused with [14C]polyethtyleneglycol ([14C]PEG)-labeled lactated Ringer's solution (LR) at 0.1 ml/min. Effluent from the common bile duct was collected at 5-min intervals during 30-min intravenous infusions of LR, LR + 2% serum albumin, and LR + 2% serum albumin + bovine PP (10 and 50 ng/kg/min). Gallbladder pressure was continuously recorded. Total and incremental fillings were calculated based on volume and [14C]PEG concentration changes. Infusion of PP, 50 ng/kg/min, induced significant gallbladder filling. The filling response was progressive and peaked during the final 10 min of peptide infusion. These findings coupled with the observation that serum PP levels are increased for up to 6 hr postprandially suggest that PP may play an important role in the regulation of interdigestive gallbladder filling.