Formation of Bile Acids in Hemoglobin-Free Perfused Rat Livers

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Abstract
The formation of bile acids was studied in isolated rat livers perfused with Krebs-Ringer bicarbonate buffer (pH 7.4)-5.5 mM glucose oxygenated with O2/CO2 (95: 5). When livers were perfused with 150 ml of the medium in a recirculating system, bile was secreted at a rate of around 30 mg/g liver/h during a 3-h period. Gas chromatographic analysis of biliary bile acid components gave the following results. As regards cholic acid, after that present in the hepatic pool was washed out during the initial 0.5 h, secretion of de novo cholic acid at a level of about 3 nmol/g liver/h lasted for at least 2 h. The pattern of bile acid was essentially similar to that in bile-fistula rats. However, secretion of β-muri-cholic acid relative to cholic acid increased more than 60% in the perfusion period of 1.5–2.5 h compared with that in the period of 0.5–1.0 h. In tracer experiments with [24-14C]chenodeoxycholic acid, no accelerated incorporation into α- and β-muricholic acids was observed in the perfusion period of 1.5–2.5 h, as compared with that of 0.5–1.5 h. Specific radioactivity of muricholic acids, especially of β-muricholic acid, was far lower than that of chenodeoxycholic acid. These data suggest the existence of a compartmentalized pool of endogenous chenodeoxycholic acid.