Influence of sex steroid hormones on rat growth hormone-releasing factor and somatostatin in dispersed pituitary cells.
The modulatory effects of glucocorticoid and sex steroid hormones on the effects of rat GH-releasing factor (GRF) and somatostatin (SRIF) on GH release and biosynthesis were studied in monolayer cultures of rat anterior pituitary cells with RIA and quantitative immunoprecipitation methods. Dexamethasone (10(-7) M), a potent synthetic glucocorticoid, increased both the sensitivity and maximum response of GH release stimulated by GRF. Progesterone (10(-7) M) also enhanced GH release stimulated by GRF. The stimulatory effects of dexamethasone and progesterone were dose dependent and required a latent period of at least 24 h to be evident. Testosterone, dihydrotestosterone, and 17 beta-estradiol showed no apparent influence on GRF-induced GH release under the same conditions. None of the hormones studied showed significant influences on basal or SRIF-suppressed GH release. Progesterone added to the maximally effective concentrations of dexamethasone had no additional effects on GRF-induced GH release. The effect of progesterone was attenuated by both 5 alpha-dihydronorethindrone, a progesterone antagonist and 17 alpha-methyltestosterone, a glucocorticoid antagonist. In terms of GH synthesis, stimulatory effects of GRF on GH synthesis were apparent only when pituitary cells were pretreated with dexamethasone. These results indicate that: pretreatment with glucocorticoid or progesterone enhances the effects of GRF on GH release and/or synthesis; these two steroids share at least one common step to enhance GRF effects; and steroid hormones have little influence on basal or SRIF-suppressed GH release.
D000818:Animals; D003907:Dexamethasone / Q000494:pharmacology; D013196:Dihydrotestosterone / Q000494:pharmacology; D004958:Estradiol / Q000494:pharmacology; D005260:Female; D005485:Flutamide / Q000494:pharmacology; D012739:Gonadal Steroid Hormones / Q000494:pharmacology*; D013007:Growth Hormone-Releasing Hormone / Q000378:metabolism*; D008777:Methyltestosterone / Q000494:pharmacology; D009640:Norethindrone / Q000031:analogs & derivatives / Q000494:pharmacology; D010902:Pituitary Gland / Q000187:drug effects* / Q000378:metabolism; D011374:Progesterone / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D013004:Somatostatin / Q000378:metabolism*; D013739:Testosterone / Q000494:pharmacology
D012739:Gonadal Steroid Hormones; D013196:Dihydrotestosterone; D013739:Testosterone; D011374:Progesterone; D004958:Estradiol; D013004:Somatostatin; C014485:5 alpha-dihydronorethindrone; D005485:Flutamide; D003907:Dexamethasone; D013007:Growth Hormone-Releasing Hormone; D009640:Norethindrone; D008777:Methyltestosterone