ABSTRACT
The aim of the present work was to study the effects of the antiestrogen tamoxifen 9TAM) of progestin noresthisterone acetite (NA) and of their combination on serum prolactin levels, uterine growth and the presence of uterine immunoreactive prolactin estradiol- treated rats. Ovariectomized female Wistar rats were injected sc with estradiol valerate (VE, 50 µg/rat per week) or oil vehicle. During the secon week, estradiol-treated rats also received NA (0.12 or 1.0 mg/eat, sc, daily) or TAM (0.06 mg/rat) alone or in combination with NA (0.12mg). Serum prolactin levels were suppressed to the same extent in the TAM- and 1.0 mg NA-treated groups compared with rats given estrogen alone (2.3 ñ 0.3 and 5.6 ñ 1.5 ng/ml for TAM and NA groups vs 39.7 ñ 3.6 ng/ml for VE groups, P < 0.05). Except for the lowes dose of NA, uterine wet weight and DNA content were significant reduced in all groups compared to estradiol alone (236.8 ñ 18.0 and 295.6 ñ 27.8 mg vs 309.4 ñ 32.2 mg for uterine weight in TAM and NA groups vs VE, respectively, P 0.05; and 1.14 ñ 0.05 and 0.93 ñ 0.04 mg/uterus vs 1.33 ñ 0.06 mg/uterus for uterine DNA in TAM and NA groups vs VE groups). The combination of NA and TAM resulted in a higher degree of suppression of uterine growth than when each drug was used alone, indicating an additive antiproliferative effect of NA and TAM. Although no prolactin immunostaining was detected in the uterus of rats treated with estradiol, uterine immunoreactive prolactin was identified in those treated with NA, TAM ot both. These results suggest that an inhibitory effect on the action of estradiol can play a role in the hormonal modulation of uterine secretion