Stimulation vivo of testicular 7α-hydroxylase activity in immature rats by LH and hCG

Abstract

Testicular C 19-steroid 7α-hydroxylase activity rises during puberty in the rat. Hormonal mechanisms responsible for this rise are unknown. The present study is to the best of our knowledge the first to report successful stimulation of testicular 7α-hydroxylase in immature rats. Administration of crude and purified hCG every day for 3 or more days to immature rats in doses of 3 I.U. lead to significant stimulation of testicular 7α-hydroxylase activity. Purified preparations of subunits of hCG did not stimulate 7α-hydroxylase activity. Stimulation of testicular 7α-hydroxylase was, however, recorded when purified subunits of hCG were allowed to recombine and then administered to the animals. Several preparations of LH failed to cause stimulation of 7α-hydroxylase when administered to immature rats. Treatment of immature rats with mixtures of LH and FSH, LH and prolactin or LH togethtr with FSH and prolactin was also ineffective in this respect. Large doses of highly purified ovinc-LH, rat LH and human LH were. however, able to stimulate testicular 7α-hydroxylase activity in immature rats. Preparations comprising hybrids of ovine-LH and hCG (oLHα + hCGβ, hCGα + oLHβ) stimulated testicular 7α-hydroxylase activity in immature rats. Administration of the same amounts of a hybride preparation of human and ovine-LH (oLHa + hLHβ) to immature rats was ineffective in this respect. Administration of testosterone or estradio] to immature rats lead to supression of testicular 7α-hydroxylase activity. Combined treatment of such rats with hCG and testosterone or with estradiol and hCG augmented testicular 7α-hydroxylase activity to the same degree as that of animals treated with hCG only.