BILE SALT-DEPENDENT INHIBITION OF GALLBLADDER EMPTYING

Little is known about the inhibitory controls of gallbladder emptying. Since cholestyramine, a binding agent that reduces luminal concentrat ion of bile salt, has been reported to accelerate gallbladder emptying , suggesting that bile salt is inhibitory, we hypothesized that fat-st imulated gallbladder emptying is inhibited by a bile salt-dependent me chanism. To test this idea, we compared gallbladder emptying in 10 dog s equipped with duodenal and jejunal fistulas that allowed for complet e diversion of the native bile while varying concentrations of bile sa lt were perfused into the small intestine. In six dogs, 30 mM oleate a nd 5, 10, or 20 mM sodium taurocholate was perfused into the whole int estine. Since bile salt availability alters fat absorption, in a separ ate experiment in seven dogs we also compared gallbladder emptying whi le 30 mM oleate and 5 mM taurocholate were perfused between fistula an d 0, 5, 10, or 20 mM taurocholate were perfused beyond jejunal fistula to separate fat from varying concentrations of bile salt. We found th at intestinal taurocholate inhibited fat-stimulated gallbladder emptyi ng in a dose-dependent fashion (P < 0.01; analysis of variance, signif icant linear dose effect) and that the inhibitory effect of bile salt persisted when 5-20 mM taurocholate was perfused beyond the jejunal fi stula (0 vs. average of 5-20 mM taurocholate, P < 0.05, paired t-test) . We conclude that fat-stimulated gallbladder emptying is inhibited by a bile salt-dependent inhibitory mechanism.