Measurement of conjugated 1 beta-hydroxycholic acid in urine of newborns by specific radioimmunoassay.

Anti-tauro 1 beta-hydroxycholic acid antisera were prepared by immunizing rabbits with N-(1 beta,3 alpha,7 alpha,12 alpha-tetrahydroxy-5 beta-cholan-24-oyl)glycine bovine serum albumin conjugate. The immunoglobulin G fraction was obtained by ammonium sulfate precipitation, followed by diethylaminoethyl cellulose column chromatography. The antibody was characterized using [2-3H]tauro 1 beta-hydroxycholic acid which has a high affinity (Ka = 1.09 x 10(9) M-1) and reasonable specificity. Cross-reactivity for glyco 1 beta-hydroxycholic acid was 100% and those for other 1 beta-hydroxylated bile acids ranged from 4.32 to 29.6%. Concentrations of conjugated 1 beta-hydroxycholic acid in urine of newborns at 0-20 d after birth were determined by radioimmunoassay to be significant (0.2-11.1 micrograms/ml), exhibiting a tendency to increase during the 20 d after birth.

A radioimmunoassay for tauro-beta-muricholic acid suitable for use with isolated rat liver cells.

A new radioimmunoassay which can be used to measure the amounts of tauro-beta-muricholic acid produced by isolated rat hepatocytes in vitro is described. Cross reactivities of other bile acids known to be present in rat liver with the antiserum used in the assay were not sufficient to interfere with the measurement of tauro-beta-muricholic acid. Exogenous taurochenodeoxycholic acid was metabolised by isolated rat hepatocytes concurrently with the appearance of tauro-beta-muricholic acid in the cell.

A highly specific 125I-radioimmunoassay for cholic acid conjugates.

Several modifications of the immunization procedure permitted development of a highly specific radioimmunoassay (RIA) for cholic acid conjugates. Antiserum was produced in guinea pigs using cholic acid-thyroglobulin complex as immunogen. 125-I-Cholyglycylhistamine was prepared as radioactive ligand according to a modification of the method of Spenney et al. (Spenney, J.G., Johnson, B.J., Hirschowitz, B.I., Mihas, A.A. and Gibson, R. (1977) Gastroenterology 72, 305--311). The association constant of the antisera to taurocholic acid was 1.8 x 10(7) l/mol, the working range of the assay between 9.5--890 pmol. Cross-reactivities of the antiserum to bile acids other than cholic acid species were less than 3%, which is lower than for any published bile acid RIA. Concentrations of cholic acid conjugates in sera obtained from 17 healthy fasting volunteers ranged from 0.4--1.9/mumul/l.