Selective Suppression of Follicle-Stimulating Hormone Secretion in Anterior Pituitary Cells by the Gonadal Steroid 3α-Hydroxy-4-Pregnen-20-One*

Abstract

The effect of 3 alpha-hydroxy-4-pregnen-20-one (3HP), a Sertoli cell steroid, on the secretion of gonadotropins from rat anterior pituitary cells in culture was examined and subsequently compared with the action of other gonadal steroids and steroids structurally related to 3HP. Pituitary cells from randomly cycling, sexually mature female rats were isolated and maintained in culture 72 h before use. On the day of treatment, medium was changed, steroids (10(-16)-10(-4) M) and/or LHRH (10(-8) M) were added, and cells were allowed to incubate for a further 24 h. Medium was then examined for gonadotropin content by RIA. 3HP treatment of anterior pituitary cells resulted in a significant reduction of both basal and LHRH-induced FSH secretion, while LH secretion was unaffected. The lowest effective dose of 3HP (10(-16) M) significantly decreased basal FSH secretion to 65.6% of control levels. The lowest effective dose of 3HP that significantly inhibited (by 31%) LHRH-induced FSH secretion was 10(-14) M 3HP. Maximum suppression by 3HP of basal FSH secretion occurred between 10(-10)-10(-8) M, and maximum suppression of LHRH-induced secretion occurred at 10(-12) M. None of the other gonadal steroids tested (progesterone, testosterone, 5 alpha-dihydrotestosterone, 17 beta-estradiol, 20 alpha-hydroxy-4-pregnen-3-one, and 5 alpha-pregnane-3,20-dione) had a similar selective effect on FSH secretion; progesterone, testosterone, and 17 beta-estradiol actually resulted in increased FSH release, and 5 alpha-pregnane-3,20-dione resulted in significant increase in basal LH. A number of metabolites and structural variations of 3HP were examined in this in vitro system at concentrations of 10(-12)-10(-6) M, and none exhibited a similar selective FSH-suppressing activity as 3HP. The data suggest that the selective FSH-suppressing effect of 3HP seen previously in vivo and here in vitro is due to 3HP itself and not the result of a metabolite of this molecule.