Pathway from progesterone to 5alpha-reduced c19 steroids not involving androstenedione and testosterone in immature mouse testes in vitro.

Testicular homogenates from mice of 23 and 70 days of age were incubated for 3-120 min with either 3-H-progesterone, 14-C-progesterone, 3-H-5alpha-pregnane-3,20-dione or 14-C-progesterone plus 3H-5alpha-pregnane-3,20-dione in the presence of NADPH. After incubation, radioactive products were purified and identified by column and paper chromatography, with derivative formation and recrystallization to constant specific activity. In immature mouse testes, the results indicate two biosynthetic pathways leading to C19 steroids from progesterone, one from progesterone via 17-hydroxyprogesterone and androstenedione to testosterone and a second via 5alpha-reduced C21 steroids to 5alpha-reduced C19 steroids such as androsterone and 5alpha-androstane-3alpha,17beta-diol. In adult mouse testes, very few 5alpha-reduced metabolites of all the delta-4-3-ketosteroids are shown to be produced from progesterone, while evident 17alpha-hydroxylation of 5alpha-pregnane-3,20-dione followed by C17-20 lyase reaction is demonstrated.