Influence of administered testosterone upon testicular enzymes of rats related to androgen formation.

Abstract

Male rats of the Wistar strain aged two months were administered testosterone propionate (1mg daily for 21 or 31 days), to examine its effect upon biosynthesis of androgen in testes and change of androgen biosynthesis due to withdrawal of androgen. The testicular homogenates and microsomal fractions of thus treated and control rats were incubated with 14C-labelled precursors such as pregnenolone, progesterone, 17α-hydroxyprogesterone and androstenedione. Androgen formation from progesterone by testicular homogenates was remarkably supressed by the administration of testosterone propionate and almost all progesterone added as substrate was recovered as itself. On the 11th day after termination of testosterone propionate administration, consumption of progesterone by the homogenate became increased almost comparable to the one of the control group, but 17α-hydroxyprogesterone and androstenedione were accumulated in the medium and formation of testosterone remained still poor, in comparison with those of control group. Activities of 17α-hydroxylase, the C17-C20 lyase and 17β-hydroxysteroid dehydrogenase were strongly reduced by the administration of testosterone propionate, but the activity of Δ5-3β-hydroxysteroid dehydrogenase was slightly reduced by the administration of either testosterone propionate or enantate. On the 11th day after withdrawal of testosterone propionate, activities of 17α-hydroxylase and the C17-C20 lyase were completely recovered to the control levels, while the activity of 17β-hydroxysteroid dehydrogenase remained still reduced at low level.