Metabolism of 5 beta-cholestane-3 alpha, 7 alpha, 12 alpha, 26-tetrol and 5 beta-cholestane-3 alpha, 7 alpha, 12 alpha, 25-tetrol into cholic acid in normal human subjects.

Side chain oxidation and cleavage of precursors in cholic acid synthesis is thought to involve initial hydroxylation at either position 25 or 26 of the side chain. Therefore, the conversion of 5 beta-cholestane-3 alpha, 7 alpha, 12 alpha, 26-tetrol and 5 beta-cholestane-3 alpha, 7 alpha, 12 alpha, 25-tetrol into cholic acid was studied in normal subjects after single intravenous injections of these labeled alcohols. Eighty-six percent and 82% of 5 beta-cholestane, 3 alpha, 7 alpha, 12 alpha, 26-tetrol was converted into cholic acid in two subjects, respectively. However, only 14 and 16% of the injected 5 beta-cholestane-3 alpha, 7 alpha, 12 alpha, 25-tetrol was converted into cholic acid in two subjects, respectively. Thus, this study indicates that 5 beta-cholestane-3 alpha, 7 alpha, 12 alpha, 25-tetrol is an inefficient substrate for cholic acid biosynthesis in man and that the major route of cholic acid synthesis probably involves the 26-hydroxylated intermediate.