Cholyltaurine absorption by the isolated vascularly perfused rat small bowel

Isolated, vascularly perfused, rat duodenojejunum and ileum preparations were used to study the transport parameters of cholyltaurine (C-tau; taurocholate). After a bolus administration of C-tau containing trace amounts of [3H]C-tau into the lumen of the isolated vascularly perfused duodenojejunum, the rate of appearance of C-tau in the portal effluent was dose-dependent over the range 5-20 mM. At a concentration of 20 mM, the rate of absorption was constant over time and amounted to 1.25 nmol.min-1.cm-1; 2.6% of the luminal load of C-tau was recovered in the portal effluent over the 40-min experimental period. Intra-arterial infusion of ouabain (10(-3)M) did not modify significantly the absorption rate of C-tau. The C-tau absorption from the lumen of the isolated vascularly perfused ileum was 7-fold higher than that from the duodenojejunum. Total absorption of C-tau was dose-dependent over the range 1-20 mM and the estimated Km and Tmax of the absorptive area of the rat ileum were 11.5 mM and 17.7 nmol.min-1.cm-1, respectively. Intraarterial infusion of ouabain reduced by 84% the recovery of C-tau in the portal effluent. In conclusion, the absorption parameters of bile acids in the duodenojejunum and in the ileum of the ex vivo rat intestinal preparations are consistent with a passive diffusion process in the proximal small intestine and an active transport in the ileum. The isolated vascularly perfused duodenojejunum and ileum preparations are therefore appropriate models for studying bile acid absorption process and the coupling with the associated local metabolic, motor, secretory and vascular events.