title: Selective release of luteinizing hormone by 3 alpha-hydroxy-5 alpha-pregnan-20-one in immature ovariectomized estrogen-primed rats.
abstract: This study investigated the role of 3 alpha-hydroxy-5 alpha-pregnan-20-one (3 alpha,5 alpha-THP) in the modulation of gonadotropin secretion using the immature ovariectomized (OVX) rat primed with a low dose of estradiol. A treatment regimen of either 0.2 or 0.4 mg/kg of 3 alpha,5 alpha-THP given in conjunction with estradiol for 4 days significantly increased levels of serum luteinizing hormone (LH) but had no effect on serum follicle-stimulating hormone (FSH). Estrogen-primed rats receiving a single injection of 3 alpha,5 alpha-THP at 0930 h showed an increase in serum and pituitary LH levels at 1200 h and 1500 h. At 1800 h, only pituitary levels of LH remained significantly higher than controls. An injection of 3 alpha,5 alpha-THP at 1230 h in estrogen-primed rats resulted in enhanced levels of pituitary LH at 1500 h and elevated levels of both serum and pituitary LH at 1800 h. When 3 alpha,5 alpha-THP was given at 0930 h and 1230 h, elevated serum levels of LH were maintained for over 6 h. The administration of pentobarbital (Pb) 30 min after an injection of 3 alpha,5 alpha-THP at 0930 h or 1230 h prevented the increases in serum LH at 1200 h, 1500 h or 1800 h. This suggests that LH-releasing hormone (LHRH) is involved in mediating the LH response by 3 alpha,5 alpha-THP. There was no change in the sensitivity of the pituitary to LHRH following 3 alpha,5 alpha-THP treatment, indicating the absence of a pituitary effect of this steroid.
mesh_terms: D000818:Animals; D002369:Castration; D004958:Estradiol / Q000494:pharmacology; D005260:Female; D005640:Follicle Stimulating Hormone / Q000378:metabolism; D007987:Gonadotropin-Releasing Hormone / Q000494:pharmacology; D007986:Luteinizing Hormone / Q000097:blood / Q000378:metabolism*; D010424:Pentobarbital / Q000494:pharmacology; D010902:Pituitary Gland / Q000187:drug effects / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains
chemical_list: D007987:Gonadotropin-Releasing Hormone; D004958:Estradiol; D007986:Luteinizing Hormone; D005640:Follicle Stimulating Hormone; D010424:Pentobarbital