Corticosteroid Regulation of Gonadotropin Secretion and Induction of Ovulation in the Rat

Abstract

In the human polycystic ovarian syndrome, glucocorticoids have been demonstrated to have beneficial effects in inducing ovulation in a number of cases. These beneficial effects were assumed to be due to suppression of adrenal overproduction of androgens. However, the possibility exists that glucocorticoids may directly regulate gonadotropin secretion and thereby improve menstrual rhythm and ovulatory activity. Herein, we report that the corticoid, deoxycorticosterone, and the synthetic glucocorticoid, triamcinolone acetonide, like progesterone (P4), are able to induce luteinizing hormone and follicle-stimulating hormone surges and facilitate ovulation in the pregnant mare serum gonadotropin-primed rat. This effect is not shared by cortisol. Prolactin release was also stimulated by deoxycorticosterone, cortisol, and progesterone, but not by triamcinolone acetonide. Similar to progesterone, triamcinolone acetonide and deoxycorticosterone administration caused a loss of fluid retention in the uterus. This effect of triamcinolone acetonide and deoxycorticosterone may be related to progesterone action as opposed to anti-inflammatory action since cortisol had no effect on uterine fluid retention. These findings raise the possibility that the beneficial effects seen with glucocorticoids in inducing ovulation in polycystic ovarian syndrome may be due in part to their direct effects upon the release of gonadotropins.

Endogenous Excitatory Amino Acid Involvement in the Preovulatory and Steroid-Induced Surge of Gonadotropins in the Female Rat*

“…Trunk blood was collected and allowed to clot for 12 h at 4 C, after which the blood was centrifuged at 2500 rpm for 30 min at 4 C, and serum was separated and stored at -20 C for subsequent RIA of LH, FSH, and PRL. Peak values for the LH surge occur later in the PMSG-treated and cycling rat than in the progesterone-treated estrogen-primed ovariectomized rat (1800 h vs. 1400 h, respectively) (13,19,22); therefore, it was decided to administer two injections of MK801 (0.2 mg/kg BW) at 1100 and 1500 h to ensure adequate blockade of NMDA neurotransmission throughout the critical period and the afternoon of proestrus.…”

Dexamethasone Enhances Fertility and Preovulatory Serum Prolactin Levels in eCG/hCG Primed Immature Rats

“…restraint), presumably activating the endogenous hypothalamic-pituitary-adrenal axis, can enhance ovulation and increase fertility [26]. These stimulatory effects have been reported in rodent models, especially the rat, usually following treatment with dexamethasone (DEX) but triamcinolone acetonide, corticosterone and cortisol have also been used and some of these compounds give similar results [23,27]. Prior studies did not assess whether DEX-enhanced reproductive function also impacted fertility or offspring quality.…”

“…Synthetic corticoids variably stimulate the release of pituitary hormones, follicle stimulating hormone (FSH), luteinizing hormone (LH) and prolactin (PRL) [21], enhance FSH action in the follicular phase of the cycle [10], and may accelerate the timing of ovulation and increase the number of oocytes released [22][23][24][25]. In addition, acute exposure to stressful stimuli (e.g.…”

Progesterone Suppression of Glutamic Acid Decarboxylase (GAD₆₇) mRNA Levels in the Preoptic Area: Correlation to the Luteinizing Hormone Surge

“…The immature ovariectomized estrogen-primed, pro gesterone-treated female rat was used in these studies due to our extensive experience with this model in inducing a gonadotropin surge which is similar in amplitude and duration to the preovulatory surge exhibited by the nor mally cycling rat and its attenuation by RU486 [22,26,[28][29][30][31][32], Estrogen treatment of ovariectomized immature rats for 2 days resulted in the suppression of basal LH levels and estradiol by itself did not induce an LH surge ( fig. 1).…”