LH-Induced Testicular Steroid Secretion After FSH Treatment in Immature and Young Adult Hypophysectomized Male Rats

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Abstract
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 μg/100 g body weight of NIAMDD-oFSH-13 or saline. On the sixth day the rats received either 15 μg/100g 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 5α dihydrotestosterone was elevated but not significantly. In young adults, FSH pretreatment resulted in increased levels of androstenedione, testosterone, and 5α 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 17α hydroxylase, the C17-C20 lyase as well as the 17β hydrosysteroid dehydrogenase at puberty. Additionally, FSH may be involved in the maintenance of cholesterol side chain cleavage activity, the C17-C20 lyase and the 17β hydroxysteroid dehydrogenase in the adult rat.