In vitro metabolism of 3-H-androstenedione by the male rat pituitary, hypothalamus, and hippocampus.

The in vitro metabolism of 2,2-3-H-androstenedione by the pituitary, hypothalamus, and hippocampus of intact and castrated adult male rats was studied. Conversion of androstenedione to radiochemically pure 5alpha-androstanedione, testosterone, 5alpha-dihydrotestosterone, androsterone, and traces of 3alpha, 5alpha-androstanediol was demonstrated in minced preparations of the three tissues in the absence of cofactors. 5alpha-androstanedione was the metabolite formed in the highest proportion. The pituitary showed the highest enzymatic conversions followed in decreasing order by the hippocampus and the hypothalamus. Castration performed three weeks prior to the experiments resulted in a significant decrease of pituitary 17beta-old-dehydrogenase activity with a concomitant increase of 5alpha-reductase. No significant changes were observed after castration in the hypothalamus and the hippocampus.