Quantitative determination of serum bile acids using a 7alpha-hydroxysteroid dehydrogenase.

A crude 7alpha-hydroxysteroid dehydrogenase isolate from P. testosteroni requires NADP specifically and provides a simple and specific means for the determination of 7alpha-hydroxy bile acids and their conjugates. A specific and reliable enzymatic-fluorimetric method for the quantitative measurement of the primary bile acids in serum is described. Overall recovery from normal and jaundiced serum averaged 85%. The mean concentration of serum 7alpha-hydroxy bile acids in fasting, healthy subjects was 2.5 mumoles/1 (S.D. 1.45 AND RANGE 1.2-6.3), averaging 73% (S.D. 11.5) of the total, measured as the 3alpha-hydroxy bile acid concentration. In parenchymatous liver disease and cholestatic hepatobiliary disorders, the proportion of 7alpha-hydroxy bile acids was significantly increased, mean 92.5% (S.D. 6.6)(p less than 0.001).