Metabolism of 3alpha, 7alpha, 12alpha-trihydroxy-5beta-cholestan-26-oic acid in normal subjects with an intact enterohepatic circulation.

The formation of cholic acid from 3alpha, 7alpha, 12alpha-trihydroxy-5beta-cholestan-26-oic acid (THCA) was studied in two normal subjects. [3H]THCA and [14C]cholic acid were administered intravenously by simultaneous injection and the specific activities (percent injected amount/mumol) of [3H]- and [14C]cholic acid were measured in bile samples collected over a 5-day period. If the administered [3H]-THCA is rapidly and completely metabolized into cholic acid, the areas under the specific activity curves of [3H]- and [14C]cholic acid should be identical. In these two subjects, the area under the [3H]cholic acid specific activity decay curves was only 18.4% and 9.0% less than the area under the [14C]cholic acid specific activity decay curves. Thus, there is rapid and nearly complete metabolism of intravenously administered [3H]THCA into cholic acid.