Enzymatic determination of bile acids from liver cells with 3 alpha-hydroxysteroid dehydrogenase--a warning.

3 alpha-Hydroxysteroid dehydrogenase was used to monitor bile acid production by rat hepatocyte suspensions. Several observations suggested that the method lacked specificity and detected some other metabolites besides bile acids. This was due to a malate dehydrogenase activity present in four different commercial enzyme preparations of 3 alpha-hydroxysteroid dehydrogenase. It is concluded that considerable error can be caused by this contaminating malate dehydrogenase activity, especially in the case of low bile acid concentration in the sample.