High activity of 17α-oxidoreductase in neonatally grafted mouse testes in adult female mice

Abstract

Male and female (WB-C57BL/6)F 1 hybrid mice were used. Two testes from neonatal mice were grafted into the spleen of adult male and female mice, and the grafted testes were removed 30 and 60 days after grafting. Normal testes from 30- and 60-day old mice were also used. Testicular homogenates were incubated with [ 14C]4-androstene-3,17-dione or [ 3H]progesterone, and enzyme activities per g wet tissue and progesterone metabolism were examined. Activity of 17α-oxidoreductase in the grafted testes in females (20 nmol/g/h) was approx. 10 times the activity in the grafted testes in males or in the normal testes, whereas 17β-oxidoreductase activity in the grafted testes in females was the lowest among these testes. The bilateral ovariectomy performed 1 month before the grafting of neonatal testes, artificial cryptorchidism performed at 20 days of age, and estrogen treatment for 10 days by diethylstilbestrol pellets resulted in no significant changes in 17α-oxidoreductase activities in 30- or 60-day old grafted, cryptorchid or normal testes. The major 17-hydroxy-C 19-steroids formed in vitro from progesterone by the grafted testes in female mice were testosterone and 17α-hydroxy-4-androsten-3-one (epitestosterone), but the formation of epitestosterone was insignificant in the normal testes. The present results demonstrate for the first time that epitestosterone is formed as one of major C 19-steroids in neonatally grafted mouse testes in females but not in those in males or in normal mouse testes. However, the mechanisms remain unexplained.