Evaluation of the 3 alpha-hydroxysteroid dehydrogenase assay for ursodeoxycholic acid, and 7 oxo- and 12 oxo- bile acids.

3 alpha-Hydroxysteroid dehydrogenase (SDH) quantifies ursodeoxycholic acid, 3 alpha,12 alpha-diol-7-one-5 beta-cholanoic acid, 3 alpha-ol-7-one-5 beta-cholanoic acid, and 3 alpha,7 alpha-diol-12-one-5 beta-cholanoic acid in a manner similar to the more commonly measured bile acids, exemplified by taurocholic acid. The type of oxygen function at the 7 or 12 position and its orientation at the 7 position has no effect on the rate of reaction of the enzyme. Discrepancies in the glycine/taurine ratios of patient intestinal aspirates containing ursodeoxycholic acid and oxo bile acids, obtained by SDH and gas-liquid chromatographic methods are not a result of the enzyme assay procedure.