The aim of this study was to find out whether mifepristone, known mainly as a substance with an antiprogesterone and antiglucocorticoid effect, also has an in vivo antiestrogenic activity on the adenohypophysis of the rat. Male Wistar rats were given chronically either estradiol-benzoate (EB, 1 mg s.c. twice a week) for a period of 12 days, or the non steroidal antiestrogen tamoxifen (1 mg/day/rat), or mifepristone (1 mg/day/rat), or EB together with mifepristone or tamoxifen. The hypertrophic effect of the EB on the weight of the adenohypophysis (AP) was significantly suppressed both by tamoxifen and by mifepristone. Mifepristone and tamoxifen reduced the increased content of PRL in the estrogenized adenohypophysis. Mifepristone but not tamoxifen significantly increased the content of the LH in the adenohypophysis of estrogen treated rats. Mifepristone and tamoxifen suppressed the increased concentration of cyclic nucleotides cAMP and cGMP in the estrogenized adenohypophysis. Mifepristone given alone increased serum levels of corticosterone, but when given together with EB deepened inhibiting effect EB on them. The results of our preliminary study show that mifepristone exerts a weak antiestrogenic activity on the level of hypophysis, however the pharmacology is not identical to tamoxifen.

• MeSH
• Pituitary Gland, Anterior drug effects   MeSH
• Estrogen Antagonists administration & dosage   pharmacology   MeSH
• Estradiol administration & dosage   analogs & derivatives   pharmacology   MeSH
• Drug Combinations MeSH
• Injections, Subcutaneous MeSH
• Corticosterone blood   MeSH
• Rats MeSH
• Mifepristone administration & dosage   pharmacology   MeSH
• Rats, Wistar MeSH
• Tamoxifen administration & dosage   pharmacology   MeSH
• Body Weight drug effects   MeSH
• Organ Size drug effects   MeSH
• Animals MeSH
• Check Tag
• Rats MeSH
• Male MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• Estrogen Antagonists MeSH
• estradiol 3-benzoate MeSH Browser
• Estradiol MeSH
• Drug Combinations MeSH
• Corticosterone MeSH
• Mifepristone MeSH
• Tamoxifen MeSH