LH-induced testicular steroid secretion after FSH treatment in immature and young adult hypophysectomized rats.

Immature and young adult male rats were hypophysectomized on day 21 and 71 respectively. Beginning 2 days later, animals received five daily subcutaneous injections of 4 microgram/100 g body weight of NIAMDD-oFSH-13 or saline. On the sixth day the rats received either 15 microgram/100 g body weight of NIAMDD-oLH-21 or saline intraperitoneally and were decapitated 1 hr later. Serum levels of steroids were measured by radioimmunoassay. Serum steroid levels in animals receiving a saline injection on day 6 were low to undetectable and not affected by pretreatment. The serum steroid concentrations after LH challenge on day 6 were altered by FSH pretreatment. In immature rats, pretreatment with FSH resulted in a significant increase in 17 hydroxyprogesterone, androstenedione and testosterone. Progesterone and estradiol were unaffected, while 5 alpha dihydrotestosterone was elevated but not significantly. In young adults, FSH pretreatment resulted in increased levels of androstenedione, testosterone, and 5 alpha dihydrotestosterone, but not progesterone, 17 hydroxyprogesterone, or estradiol. These data suggest that FSH may play a role in stimulating cholesterol side chain cleavage activity, the 17 alpha hydroxylase, the C17-C20 lyase as well as the 17 beta hydroxysteroid dehydrogenase at puberty. Additionally, FSH may be involved in the maintenance of cholesterol side chain cleavage activity, the C17-C20 lyase and the 17 beta hydroxysteroid dehydrogenase in the adult rat.