title: Dexamethasone inhibits the effects of oestrogen on the pituitary gland in rats.
abstract: The administration of glucocorticoids has been shown to be effective for the induction of ovulation in patients with anovulation. In the present study, we investigated the effects of a glucocorticoid on oestrogen-induced changes in the pituitary gland. A single ip injection of 10 micrograms oestradiol-17 beta (E2) in ovariectomized and adrenalectomized rats resulted in a significant increase in pituitary weight and progesterone receptor (PgR) concentration. In these animals, serum LH level was initially suppressed and restored to control level 24 h after E2 injection. However, 1 mg of dexamethasone (Dex) injected before E2, but not after E2 administration, completely inhibited both the increases in pituitary weight and PgR concentration. The restoration of serum LH level 24 h after E2 was also prevented. These antioestrogenic effects of Dex were blocked by ip administration of the synthetic antiglucocorticoid, RU486. Dex treatment alone did not have any effect on E2-induced changes in the dynamics of pituitary oestrogen receptor. Finally, E2-pellet implanted sc in ovariectomized and adrenalectomized rats for 7 days caused marked increases in pituitary weight and PgR concentration. A single ip injection of 250 micrograms clomiphene citrate (clomiphene) significantly reduced both the pituitary weight and PgR concentration in these animals, but 1 mg of Dex failed to have a similar effect. These results suggest that glucocorticoids antagonize E2 effects on the pituitary by a mechanism different from antioestrogens such as clomiphene. These antioestrogenic effects of glucocorticoid may be involved in induction of ovulation in anovulatory women.
mesh_terms: D000315:Adrenalectomy; D000818:Animals; D002996:Clomiphene / Q000494:pharmacology; D003907:Dexamethasone / Q000494:pharmacology*; D004958:Estradiol / Q000494:pharmacology*; D004963:Estrenes / Q000494:pharmacology; D004965:Estrogen Antagonists; D005260:Female; D007986:Luteinizing Hormone / Q000097:blood; D015735:Mifepristone; D009929:Organ Size / Q000187:drug effects; D010052:Ovariectomy; D010902:Pituitary Gland / Q000187:drug effects*; D051381:Rats; D011919:Rats, Inbred Strains; D011980:Receptors, Progesterone / Q000378:metabolism; D013347:Subcellular Fractions / Q000378:metabolism
chemical_list: D004963:Estrenes; D004965:Estrogen Antagonists; D011980:Receptors, Progesterone; D002996:Clomiphene; D015735:Mifepristone; D004958:Estradiol; D003907:Dexamethasone; D007986:Luteinizing Hormone