Evidence for loss of tritium from 3 beta-tritiated deoxycholic acid during enterohepatic cycling in man.

A double-label single-intubation isotope technique was assessed for studying deoxycholic acid metabolism by simultaneous IV administration of [3 beta-3H]deoxycholic acid and [24-14C]deoxycholic acid to five healthy subjects. The 3H/14C ratio in duodenal bile fell progressively in all subjects, the mean reduction on day four being 48.8%. When the same labeled bile acids were administered to three ileostomy subjects, again the ratio fell with a mean reduction of 44.4% on day four. This fall more likely was due to hepatic exchange of tritium for hydrogen, rather than to colonic bacterial oxidation. [3 beta-3H]Deoxycholic acid should not be used to study the kinetics and metabolism of deoxycholic acid.