Regulation of plasma cholecystokinin levels by bile and bile acids in the rat.

To determine whether intraduodenal bile acids inhibit pancreatic secretion and cholecystokinin (CCK) release independent of pancreatic proteases, experiments were conducted in rats with bile and pancreatic juice chronically diverted to the ileum. Diversion of bile and pancreatic juice increased plasma CCK concentration to 19.1 +/- 4.0 pmol/L. Intraduodenal sodium taurocholate (78 mumol/h) reduced plasma CCK concentration to 6.6 +/- 1.5 pmol/L after 1 hour, but values increased to 17.3 +/- 2.3 pmol/L after 13.5 hours despite continued taurocholate infusion. Pancreatic protein secretion was also significantly but transiently inhibited by taurocholate. However, neither acute nor chronic intraduodenal bile infusion significantly reduced plasma CCK concentration compared with sodium bicarbonate infusion (13.4 +/- 1.9 pmol/L vs. 15.0 +/- 1.7 pmol/L, respectively). Chronic (13.5 hours) intraduodenal infusion of taurocholate plus pancreatic juice caused a sustained reduction of plasma CCK level to 3.1 +/- 0.5 pmol/L, which significantly increased to 9.4 +/- 1.1 pmol/L after cessation of taurocholate but with continued infusion of pancreatic juice. The results indicate that bile does not inhibit CCK release and that bile acids do not physiologically inhibit pancreatic secretion or CCK release independent of the presence of pancreatic proteases.