Sonia J. Ringstrom

Effects of corticosterone and testosterone on pituitary gonadotropin content, secretion, bioactivity and messenger RNA levels in the presence or absence of GnRH in male rats

The effects of corticosterone (B) and testosterone (T) on pituitary and serum bioactive and immunoreactive gonadotropins and on gonadotropin hormone subunit messenger RNA levels were compared in the absence of GnRH. Male rats were implanted with pellets of either cholesterol, B or T. At implantation, 2 and 4 days later half of each group received GnRH antagonist and animals were killed 5 days after implantation. As expected, GnRH antagonist lowered bioactive and immunoreactive serum FSH and LH, pituitary FSH, LHβ and FSHβ mRNA. B treatment alone lowered bioactive and immunoreactive serum FSH and immunoreactive serum LH. B reversed the antagonist effect on bioactive and immunoreactive pituitary FSH and FSHβ mRNA. T alone lowered bioactive and immunoreactive serum FSH and LH levels. T reversed the antagonist effect on bioactive and immunoreactive pituitary FSH. T lowered bioactive and immunoreactive pituitary LH and LHβ mRNA and partially reversed the antagonist effect on FSHβ mRNA. The data suggest that either B or T enhance FSH synthesis by acting directly at the gonadotrope, but that B does not affect LH variables to the same extent as T. The results suggest that in stressed animals, when T levels are reduced, B can substitute for T in sustaining FSH synthesis.

Effects of in Vivo Exposure to Glucocorticoids on Pituitary, Serum, and Messenger Ribonucleic Acid Levels of the Gonadotropin Hormones FSH and LH in Male

Publisher Summary Glucocorticoids (both corticosterone, the native glucocorticoid in the rat, and cortisol) have different effects on the two anterior pituitary hormones, luteinizing hormone (LH) and follicle-stimulating hormone (FSH), which regulate reproductive processes. Sustained exposure to high levels of glucocorticoids, such as those present in a stress response, suppresses serum levels of LH, while not affecting or only minimally affecting pituitary content of LH in both sexes. This suggests that glucocorticoids inhibit the release of LH from the gonadotropes. In contrast, high levels of circulating glucocorticoids do not affect or only slightly affect serum levels of FSH, but increase pituitary content of FSH in both sexes. This indicates that glucocorticoids either increase synthesis or block the degradation of FSH in the gonadotropes. Treatment of male rats with elevated levels of cortisol caused a decrease in serum LH, but pituitary content of LH was not affected; immunoreactive serum FSH was not affected in males treated with cortisol; pituitary content of FSH was increased in male rats treated with cortisol; and cortisol treatment completely reversed the effects of a gonadotropin-releasing hormone (GnRH) antagonist on pituitary FSH in female rats.