In vivo metabolism of 3H-testosterone in adult male rats: Effects of estrogen administration

Abstract The metabolism of testosterone (T) was studied in normal adult male rats using a constant infusion of trace amounts of the 3 H-steroid into a tail vein for 3 h in order to attain a state of equilibrium. Samples of plasma, liver, kidney, prostate, seminal vesicles and muscle were analysed for 3 H-testosterone, 3 H-5α-dihydrotestosterone (5αDHT) and 3 H-5α-androstanediol (Adiol). When compared to the 3 H-T level in plasma there were high levels of 3 H-T in kidney and of 3 H-5αDHT in prostate and seminal vesicles. Intraperitoneal estradiol valerate administration (100 μg/ day) for 4 days decreased the 3 H-T levels in kidney and increased the 3 H-T and 3 H-5αDHT levels in the prostate and seminal vesicles. The estrogen administration increased the T metabolic clearance rate from 17.5 1/24 h/ 100 g body wt to 22.6 1/24 h/100 g body wt.