Differential effects of in vitro glucocorticoids on luteinizing hormone and follicle-stimulating hormone secretion: dependence on sex of pituitary donor

We have used a dynamic perifusion system to determine whether glucocorticoids exert a direct effect on the secretion of LH and FSH from rat anterior pituitaries. Anterior pituitary fragments from male, proestrous female, or metestrous female rats were perifused for 8 h in either the absence (basal secretion rate) or presence of pulsatile GnRH administration (50 ng/ml peak concentration). Perifusions used medium containing 0.05% ethanol (vehicle), 600 ng/ml corticosterone, or 600 ng/ml cortisol. GnRH-stimulated secretion of FSH was enhanced in pituitaries from both male and female rats after in vitro incubation with either corticosterone or cortisol. The basal secretion rate of FSH was also elevated in proestrous females after glucocorticoid treatment. The GnRH-stimulated secretion rate for LH was significantly decreased in pituitaries from male rats treated with either glucocorticoid. In contrast, pituitaries from proestrous rats responded to either cortisol or corticosterone with an increase in LH secretion. Metestrous pituitaries showed divergent effects of the glucocorticoids on LH secretion; corticosterone enhanced secretion rates, and cortisol effected a decrease. Our data demonstrate that 1) glucocorticoids exert a direct effect on the secretion of LH and FSH from male and female rat pituitaries; 2) glucocorticoids elicit different effects on the secretion of LH and FSH, suggesting that they act at separate sites to regulate LH and FSH secretion; and 3) the effect of in vitro glucocorticoid treatment on gonadotropin secretion is dependent on sex and cycle stage of the pituitary donor and may be linked to prior in vivo concentrations of estrogen.