Uptake of bile acids by perfused rat liver.
The uptake of 14C-labeled cholic, taurocholic, and chenodeoxycholic acid by the perfused rat liver was studied to characterize the mechanism responsible for hepatic uptake of bile acids. A rapid-injection multiple indicator-dilution technique and the three-compartment model of Goresky were employed. The kinetics of hepatic uptake of the three bile acids could be described by the Michaelis-Menten equation. The maximal uptake velocities (Vmax) were 24.9 +/- 2.2 (mean +/- SD), 20.8 +/- 1.2, 1.2, and 11.4 +/- 0.9 nmol/s-g liver for cholic, taurocholic, and chenodeoxycholic acid, respectively. The corresponding apparent half-saturation constants (Km) were 526 +/- 125, 258 +/- 43, and 236 +/- 48 nmol/g liver. Competitive inhibition could be demonstrated between cholate and taurocholate as well as between cholate and chenodeoxycholate. Substitution of 94% of the Na+ in the perfusion medium decreased the Vmax and the apparent Km of taurocholate uptake by 68 and 55%, respectively. These findings are consistent with the hypothesis that bile acids are taken up into the hepatocyte by Na+-dependent carrier-mediated transport.
D000818:Animals; D001647:Bile Acids and Salts / Q000378:metabolism*; D001667:Binding, Competitive; D001692:Biological Transport; D002635:Chenodeoxycholic Acid / Q000378:metabolism; D002793:Cholic Acids / Q000378:metabolism; D066298:In Vitro Techniques; D007201:Indicator Dilution Techniques; D007700:Kinetics; D008099:Liver / Q000378:metabolism*; D008297:Male; D051381:Rats; D012964:Sodium / Q000378:metabolism; D013656:Taurocholic Acid / Q000378:metabolism
D001647:Bile Acids and Salts; D002793:Cholic Acids; D002635:Chenodeoxycholic Acid; D013656:Taurocholic Acid; D012964:Sodium