Evaluation of the ileal absorption capacity for bile acids in the rabbit

The intestinal absorption of bile acids has so far been studied from the measurement of the biliary secretion after their intestinal infusion. In the present investigation, the ileal absorption capacity for two different bile acids has been evaluated by means of an intestinal perfusion technique and the simultaneous blood drainage from the mesenteric vein corresponding to the isolated loop. Taurocholic acid and unconjugated cholic acid were infused at different concentrations (0.5-10.0 mM), at a flow rate of 4 ml/min/cm intest. Taurocholic acid absorption increased to a maximum with dose, then reaching a plateau, suggesting that a saturable process had taken place. Cholic acid uptake showed a saturable, possibly active, process, together with a nonsaturable one. These results are consistent with the physicochemical properties of the two bile acids. The technique seems so far suitable for the study of the intestinal absorption of substances undergoing the enterohepatic circulation, since it provides a direct measure of the absorbed fraction, without any distortion arising from the hepatic uptake and biliary secretion.