Effects of combined estrogen and raloxifene therapy on rat endometrium - Revista Brasileira de Ginecologia e Obstetrícia

PURPOSE: to evaluate the effects of conjugated equine estrogens (CEE) and raloxifene (Ral), alone or combined, on the rat endometrium. METHODS: fifty-six adult rats were ovariectomized and randomly divided into seven groups: GCont (control); GCEE (CEE 50 µg/kg); GCEE/25 (CEE 25 µg/kg); GRal/0.75 (Ral 0.75 mg/kg); GRal/0.4 (Ral 0.4 mg/kg); GCEERal (50/0.75) – (CEE 50 µg/kg + Ral 0.75 mg/kg), and GCEE-Ral (25/0.4) – (CEE 25 µg/kg + Ral 0.4 mg/kg). The drugs were orally administered (gavage) for 21 consecutive days. At the end of the experiment, all animals were anesthetized and sacrificed. Fragments of uterus were removed, fixed in 10% formaldehyde and processed for paraffin inclusion. The histological sections were stained by HE and submitted to histomorphometric evaluation. The following parameters were analyzed: thickness of superficial epithelium and number of endometrial glands/mm² and of blood vessels/mm². The data were evaluated using ANOVA followed by the Turkey-Kramer test. RESULTS: in the GCont and only Ral treatment (GRal/0.75 and GRal/0.4) the endometrium showed signals of atrophy. In the groups treated with only CEE signs of endometrial proliferation were observed, mainly in group GCEE/50. Also, there was endometrial proliferation in the groups that received combined CEE and Ral (Ral GCEE (50/0.75) and GCEE-Ral (25/0.4)), but it was more intensive in the animals treated with isolated estrogen than in those that received combined estrogen and raloxifene. CONCLUSION: raloxifene may partially block the action of estrogen on the castrated adult rat endometrium.