ENZYME-IMMUNOASSAY FOR CONJUGATED CHOLIC AND 1-BETA-HYDROXYCHOLIC ACIDS IN URINE OF EARLY INFANCY

A direct competitive heterologous enzyme immunoassay (EIA) for conjuga ted cholic acid (CA) was developed using horseradish peroxidase labele d antigen having a shorter bridge length than that of the immunogen. A n appropriate dose-response curve for conjugated CA was obtained in th e range of 0.05-50 ng/well. Specificity of the EIA proved satisfactory in terms of cross-reactivities to 23 kinds of related bile acids. The proposed method was evaluated to be useful for the determination of c onjugated CA in urine with acceptable accuracy and inter- and intraass ay precision. The results of analysis showed a reverse relationship be tween age and urinary excretion ratio of conjugated 1 beta-hydroxy-CA to conjugated CA in the first 9 months after birth.