SERUM C-24 BILE-ACIDS IN THE DEVELOPING HUMAN FETUS

The C-24 bile acids (BA) in the serum of 22 healthy human fetuses betw een weeks 20 and 37 of gestation were determined by capillary GC-MS. F etal blood samples were taken in utero from the umbilical cord monitor ed by echography. There was no correlation between total bile acids (T EA) and gestational age. The TEA concentration was 5.14 +/- 2.13 mu M. Primary BA (cholic acid and chenodeoxycholic acid) were the main BA ( 66.78 +/- 13.47%) with chenodeoxycholic acid being the main one. There were low concentrations of secondary BA (deoxycholic acid and lithoch olic acid) (10.28 +/- 7.85%), which formed by intestinal bacterial 7 a lpha-dehydroxylation of primary BA in the adult, despite the germ-free gut. The tertiary BA (ursodeoxycholic acid) was also detected (12.06 +/- 9.64%). There was 6 alpha-hydroxylation of chenodeoxycholic acid a nd of lithocholic acid to produce hyocholic acid and hyodeoxycholic ac id respectively. Two 1 beta-hydroxylated BA were detected at different times of gestation. Cholic acid was rarely found in the 6 alpha- and 1 beta-hydroxylated forms. These additional hydroxylations could help to protect the fetal liver against the accumulation of cytotoxic bile acids at a time when other detoxification pathways are poorly develope d. Traces of unsaturated bile acids like 3 beta-hydroxy-5-cholenoic ac id were detected, showing that 27-hydroxylation of cholesterol does oc cur.