Sex Differences in Metabolism of Testosterone by Rat Liver

Abstract

The sex differences in in vitro metabolism of testosterone in the homogenates, the microsomes or the 105, 000×g supernatant fluid of adult rat livers and the influence of estradiol-treatment or castration on the metabolism in male rats were investigated.
In the metabolism by liver homogenates, the predominant metabolites were hydroxylated testosterones in males, whereas they were androstanedione, androsterone and 5α-dihydrotestosterone in females. Most of the substrate, testosterone, was easily metabolized in females. In the microsomes, the amount of testosterone unmetabolized remaining was high in males, while most of testosterone was metabolized to 5α-androstane-3α, 17β-diol in females. In the supernatant, a large amount of testosterone remained unchanged in females, whereas it was mainly metabolized to 5β-androstane-3α, 17β-diol in males. Castration and estradiol-treatment of male rats induced the female type of metabolic pattern to some extent.