The biological activity of a single dose of tamoxifen in the adult ovariectomized rat.
1 The peripheral and central activities of tamoxifen were studied in the ovariectomized adult rat, up to 16 d after a single dose of 7.0 or 0.7 mg/kg. 2 Food consumption and body weight were decreased; only food consumption returned to control values after 16 d. 3 The weights of the uterus and of the uterine luminal fluid were increased for up to 8 d. 4 Serum follicle-stimulating hormone (FSH) concentrations decreased, but only significantly 1 and 8 d after 7.0 mg tamoxifen/kg. Serum luteinizing hormone (LH) and prolactin concentrations were elevated for up to 4 d. 5 Lordosis behaviour was absent throughout the period studied. 6 Within 3 d of administration, tamoxifen partially antagonized the oestrogen-induced changes in uterine luminal fluid, prolactin and LH secretion and lordosis behaviour. 7 Tamoxifen did not alter oestrogen-induced changes in uterine weight, food consumption and body weight. 8 The experiments demonstrate that tamoxifen is active for up to 16 d after a single intraperitoneal dose; oestrogen agonist, partial agonist and antagonist activities were demonstrated. The duration and type of activity depends upon the dose of tamoxifen and the target tissue response examined.
D000818:Animals; D001835:Body Weight / Q000187:drug effects; D002369:Castration; D004965:Estrogen Antagonists; D005247:Feeding Behavior / Q000187:drug effects; D005260:Female; D005640:Follicle Stimulating Hormone / Q000097:blood; D007986:Luteinizing Hormone / Q000097:blood; D011388:Prolactin / Q000097:blood; D051381:Rats; D011919:Rats, Inbred Strains; D012725:Sexual Behavior / Q000187:drug effects; D013629:Tamoxifen / Q000494:pharmacology*
D004965:Estrogen Antagonists; D013629:Tamoxifen; D011388:Prolactin; D007986:Luteinizing Hormone; D005640:Follicle Stimulating Hormone