Stereospecific Reduction of 3- and 7-Oxo Groups of Oxocholanic Acids in Isolated Perfused Rat Liver

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Abstract
The metabolism of 3- and 7-oxo groups of oxocholanic acids was studied in isolated perfused rat liver. The metabolites in bile were determined enzymatically using 3.alpha.- and 7.alpha.-hydroxysteroid dehydrogenases. The 3-oxo group of all the oxocholanic acids tested (dehydrocholate, glycodehydrocholate, taurodehydrocholate, 3,7-dioxocholanate, 3,12-dioxocholanate and tauro-7,12-dihydroxy-3-oxocholanate) was reduced stereospecifically to 3.alpha.-hydroxy metabolites. On the other hand, the 7-oxo group was excreted partially unchanged (30% of the dose) and partially as 7.alpha.-hydroxy metabolites (6-10% of the dose). The remainder of the 7-oxo group was concluded to have been reduced to 7.beta.-hydroxy metabolites. The 7-oxo group of oxocholanic acids is reduced predominantly to 7.beta.-hydroxy metabolites in rats rather than to 7.alpha.-hydroxy metabolites as found in man.