Direct, concentration-dependent inhibition by taurocholate of pancreatic exocrine secretion and CCK release in conscious rats

Abstract

In conscious rats, bile inhibits pancreatic secretion. The role of luminal taurocholate (TC), a major component of rat bile, in the regulation of pancreatic secretion was studied in conscious rats with external bile and pancreatic fistulae. On the fourth postoperative day, after the basal collection of bile and pancreatic juice (PJ) returned to the duodenum, graded doses of TC (0, 0.4, 4, 40 mM) containing 10 mM CaCl2 were infused into the duodenum instead of bile and PJ for 2 hr (1 ml/hr), with or without 1 mg/ml of porcine trypsin. Luminal trypsin activities were not affected by any dose of TC. The increases in pancreatic secretion in response to diversion of bile and PJ were progressively inhibited with increasing doses of infused TC from 0 mM to 4 mM both with and without trypsin infusion. The effects with 4 and 40 mM TC were not significantly different. Changes in plasma cholecystokinin concentrations roughly correlated with changes in protein output in rats without trypsin infusion. We concluded that TC directly inhibited pancreatic secretion independent of the luminal trypsin activity and that its inhibitory action was concentration dependent.