Metabolism in vivo of [3H] androstenedione and [3H] testosterone by androgen dependent tissues.

Abstract

ABSTRACT The radioactive material present in the different prostatic lobes and the seminal vesicles was isolated and identified after intramuscular injection of [1,2-3H] testosterone to adult castrated male rats. 5α-Dihydrotestosterone was the main metabolite, representing 70, 72, 49, 56 and 70%, respectively, of the total activity in the ventral, dorsal and lateral prostate, the coagulating glands and the seminal vesicles one hour after the administration of hormone. The corresponding values for unchanged [3H] testosterone were 16, 6.4, 23, 6 and 15%, respectively. In rectus abdominis muscle less than 0.3% was 5α-dihydrotestosterone, while 37% represented unconverted [3H] testosterone. Of the activity in liver, [3H]-testosterone accounted for 0.2%, whereas less than 0.1% was 5α-dihydrotestosterone. One hour after administration of [1,2-3H] androst-4-ene-3,17-dione to adult castrated rats, the uptake of radioactivity in the ventral prostate was about 2.7 times higher than in skeletal muscle. In the ventral prostate, 32% of the total activity present at this time was represented by 5α-dihydrotestosterone, while 3.5% was unmetabolized [3H] androstenedione. The corresponding values for the seminal vesicles were 24 and 3.7%, respectively. In the 105 000 × g supernatant fraction of homogenized ventral prostate tissue, part of the radioactivity was associated with soluble macromolecules one hour after the administration of [3H]-androstenedione.