Some Aspects of the Dynamics of Oxidation-Reduction of Etiocholanolone-3-3H,4-14C in Man

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Abstract
The metabolism of etiocholanolone-3-3H,4-14C has been studied in 2 subjects. There was good recovery of both isotopes as neutral urinary steroids in 4 days, with the principal portion excreted in the first day. Higher recovery of the carbon tracer was observed in both subjects; in one subject there was almost quantitative recovery of this isotope. Etiocholanolone accounted for most of the radioactivity present in these extracts, confirming earlier studies. Approximately 20% of the administered tritium appeared as body water in the 2 studies as a result of the oxidation of the 3α-hydroxyl group. This is a minimal value for the extent of dehydrogenation at C-3 since the isotope entered other nonsteroidal compounds. The oxidation of the 3α-hydroxyl group was quite rapid. By the end of the first half hour, the body water already contained over 60% of the tritium which eventually was detected in this compartment. Appreciable resynthesis of etiocholanolone from the oxidized product was demonstrated by the change in the 3H/14C ratio of the recovered steroid. Progressive decline of the isotope ratio in successive intervals further demonstrated that oxidation and reduction continued to operate throughout the study and that more than 50% of etiocholanolone isolated toward the end of the study was resynthesized steroid. Etiocholanolone conjugated as sulfate had a lower 3H/14C ratio than that conjugated as glucosiduronate. These studies show that etiocholanolone is not an inert endproduct whose sole fate is conjugation and excretion.