The effects of soy extract on the uterus of castrated adult rats

Abstract

Objective The aim of this study was to evaluate the effects of different doses of a standardized soy extract on the uterus of castrated rats. Methods Fifty-six adult castrated female Wistar rats were randomly divided into seven groups (eight animals in each) that received: GI—drug vehicle (propylene glycol); GII—soy extract 10 mg/kg per day; GIII—soy extract 50 mg/kg per day; GIV—soy extract 100 mg/kg per day; GV—soy extract 300 mg/kg per day; GVI—soy extract 600 mg/kg per day; GVII—conjugated equine estrogens (CEE) 200 μg/kg per day. After 21 days of treatment, all animals were sacrificed and fragments of the uterine horns were immediately removed, fixed in 10% formaldehyde and submitted to routine histological techniques for morphometric study. The endometrial cell proliferation index was determined with the PCNA antibody PC-10 and expressed as the percentuals of the PCNA-positive nuclei relative to the total countings. Other fragments were immediately frozen in liquid nitrogen for RNA extraction and VEGF analysis using RT-PCR technique. Results The minimal dose of soy extract that produced a significant increase of the morphometric parameters was 100 mg/kg (GIV). The maximum effects on endometrial and myometrial morphometry were detected in the groups treated with 300 and 600 mg/kg of soy extract (groups V and VI) and CEE (GVII). The expression of PCNA in the endometrial epithelium and stroma was increased by treatment with 100–600 mg/kg per day of soy extract (groups IV–VI) or with CCE (group VII). Doses equal to or higher than 50 mg/kg of soy extract (groups III–VI) and CEE stimulated the expression of VEGF. Conclusion The treatment of adult castrated rats during 21 days with doses of 100 mg/kg per day or higher of soy extract may determine significant proliferation in the endometrium and myometrium.