Indirect evidence that intestinal bile salt absorption in rats and hamsters is under positive feedback control

Bile salts are reabsorbed from the intestine by active and passive transport mechanisms with great efficacy. Conflicting data do not allow to judge for certainty whether bile salt absorption is under negative or positive feedback control. To address this issue, we analyzed bile salt absorption in vivo along the entire intestinal tract of rats and hamsters that received intraduodenal bile salt infusions for 54 h following interruption of the enterohepatic circulation. Taurocholate absorption in rats was complete, even when unphysiologically high concentrations of taurocholate were given. The combined infusion of taurocholate together with potent inhibitors of bile salt synthesis such as deoxycholate, taurodeoxycholate or taurochenodeoxycholate, failed to inhibit bile salt absorption. In the hamster, taurochenodeoxycholate and taurocholate absorption was complete and could not be inhibited when given in supraphysiological concentrations. Finally, taurocholate absorption was not impaired when deoxycholic acid was infused. These results provide indirect evidence that bile salt absorption is under positive feedback control regulated by luminal bile salt concentrations.