Serum bile acid determination after different doses of orally ingested chenodeoxycholic acid. Evaluation of a simplified enzymatic method.

A simplified enzymatic method for determination of serum 3 alpha-hydroxy bile acids (3 alpha-HBA) has been evaluated. Analytical precision was low in the normal range but satisfactory for elevated values. The fasting upper reference value was 8.0 mumol/l. In 12 healthy subjects serum 3 alpha-HBA levels were measured after oral loads (125, 250, 500, and 1000 mg) of unconjugated chenodeoxycholic acid (CDA). After the 125-mg CDA loading dose no significant increase in serum 3 alpha-HBA was observed, but with the 250 mg CDA loading dose serum 3 alpha-HBA levels were elevated at 30, 60, and 120 min. The loading doses of 500 mg and 1000 mg CDA produced significant increases in serum 3 alpha-HBA levels throughout the observation period (3 h). When sera with increased serum bile acids were analyzed by radioimmunoassay for CDA, the results correlated well with those obtained enzymatically. The usefulness of the simplified method is evident in this situation, and we also find it useful for serum bile acid determination after an oral bile acid loading test with CDA. The method is easy to perform and requires only standard laboratory equipment.