Deficiency of 5 alpha-steroid formation in guinea pig ovaries compared with immature rat and hamster ovaries.

Activities of 4-ene-5 alpha-reductase and the metabolism of progesterone were estimated in ovaries of guinea pigs, rats and golden hamsters. In the ovaries of 20-90-day old guinea pigs, the major C21-17-hydroxysteroids and C19-steroids formed from progesterone were 4-ene-3-ketosteroids, such as 17-hydroxy-4-pregnene-3,20-dione and 4-androstene-3,17-dione, and 5 alpha-C21-17-hydroxysteroids and 5 alpha-C19-steroids were not produced. In contrast, the major steroids formed by the ovaries of immature rats and immature hamsters were 5 alpha-steroids, such as 3 alpha, 17-dihydroxy-5 alpha-pregnan-20-one and androsterone, and no 4-ene-3-ketosteroids were found. The 5 alpha-reductase activity (nmol/g tissue/h) in the ovaries of immature hamsters was approx 150 times higher than those in the ovaries of guinea pigs of different ages. In contrast to rats and hamsters, the ovaries of immature guinea pigs do not form a significant amount of 5 alpha-androgens.