Fate of Cholesterol-4-C14 and -26-C14 in the Perfused Liver

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Abstract
In the isolated perfused liver chol-esterol-26-Cl4 was readily oxidized to Cl4O2- Smaller amounts appeared in the bile, both in neutral and acidic fractions. Cholesterol-4-C14 was not oxidized to C14O2- Instead, the C14 was excreted in the bile. About 10-20% of the biliary C14 was in the neutral fraction; the remainder in the bile acid fraction. Taurochenodesoxycholic acid, taurocholic acid, and an unidentified substance (compound Y) were labeled. A time study of the incorporation of C14 into these bile acids revealed that taurochenodesoxycholic acid and compound Y became labeled well before any C14 appeared in taurocholic acid. Indeed, taurochenodesoxycholic acid is the major product of cholesterol-4-C14 metabolism in the perfused liver, presumably because of the gradual breakdown of the organ before taurocholic acid has time to become dominant. The similarity of the results obtained in the present study with those in the intact animal indicates that cholesterol metabolism in the rat may be regarded, qualitatively at least, as the result of processes occurring in the liver.