1. A 7α-hydroxysteroid dehydrogenase preparation isolated from a strain of Escherichia coli provides a specific and rapid means for the determination of 7α-hydroxy bile acids and their conjugates.
2. When used in conjunction with 3α-hydroxysteroid dehydrogenase the method enables the concentrations of primary and secondary bile acids and salts in biological fluids to be determined directly without the use of thin-layer chromatography.
3. When used with thin-layer chromatography the method allows the specific quantitative determination of chenodeoxycholic acid or its conjugates in the presence of deoxycholic acid and its derivatives.