THE FATE OF C14-TESTOSTERONE AND C14-PROGESTERONE IN MICE AND RATS1,2,3

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Abstract
Following intraperit. injn. of C14_4-testosterone and C14_21_progesterone in mice and rats, radioactivity was rapidly excreted in both urine and feces. Practically all of the admd. radioactivity was recovered. About 10% of the injd. radioactivity was found in the respiratory CO2 from the animals receiving progesterone, whereas no measurable radioactivity was found in the respiratory CO2 after testosterone treatment. The tissue distr. of radioactivity in mice after testosterone admn. was studied at various time intervals and no specific localization of radioactivity was found in any organ or tissue save those concerned with the excretion of the hormone or its metabolites. Most of the radioactivity was recovered from the feces or the contents of the gastrointestinal tract. The evidence indicated that the majority was excreted in the bile and that reabsorption from the gastrointestinal tract occurred. Chemical fractionation of the excreted radioactivity could be obtained in an ether-soluble form. The conclusion was drawn that the fate of these hormones in rodents does not afford information directly applicable to the problem of steroid hormone metabolism in humans.