Effect of Somatostatin and Bombesin on Secretin-Stimulated Ductular Bile Flow in Dogs

Abstract

The effects of somatostatin and bombesin on the choleresis produced by intraduodenal acid infusion were evaluated in dogs. Because of the documented effect of these agents on hormone release, serum gastrin and plasma secretin levels were monitored. Intraduodenal acid (12 mmol/h) increased bile flow and bile bicarbonate secretion and nearly doubled systemic plasma secretin levels. Bombesin significantly increased the bicarbonate-rich choleresis produced by intraduodenal acid and increased secretin release. Somatostatin inhibited completely the choleresis produced by 12 mmol/h of intraduodenal acid but did not significantly change systemic plasma secretin levels. Subsequent studies evaluated the effects of somatostatin (10 micrograms/kg . h) on bile flow and on systemic and portal plasma secretin concentrations stimulated by exogenous secretin administration and intraduodenal acid infusion. These studies demonstrated that somatostatin did not significantly change the choleretic response or the increases in plasma secretin produced by exogenous secretin. During duodenal acid infusion, somatostatin inhibited the choleresis and significantly decreased portal plasma secretin release. Evaluation of the relationship of the increase in bile flow to the increase in portal vein secretin concentrations, as well as comparison of the degree of inhibition of bile flow with the inhibition of secretin release produced by somatostatin, indicates that secretin produces approximately 80% of the choleresis produced by acid in the duodenum. Bombesin augments bile flow stimulated by infusion of acid into the duodenum by increasing secretin release, while somatostatin decreases bile flow produced by acid in the duodenum by directly inhibiting the release of secretin from the duodenal mucosa.