PURPOSE: to evaluate histomorphometric changes in the rat myometrium upon treatment with isoflavones, as compared with estrogens, using histological and morphometric techniques. METHODS: twenty-eight oophorectomized adult rats were randomly divided into four treatment groups: GPropi = propylene glycol (control); GExtr10 - 10 mg/kg soybean extract; GExtr300 - 300 mg/kg soy bean extract; GCee - 200 µg/kg conjugated equine estrogens (Cee). Drugs or drug vehicle were administered by gavage once a day for 21 days. Upon sacrifice, the uteri were removed and weighed. Fragments of uterine horns were collected and fixed in 10% formaldehyde and processed for paraffin inclusion. The histological sections were stained by hematoxylin and eosin and evaluated microscopically by means of an image analyzer to quantify the myometrial thickness and the number of blood vessels and eosinophils. The data were studied by analysis of variance (ANOVA) followed by the Tukey-Kramer multiple comparison test. RESULTS: isoflavones in the concentration of 300 mg/kg induced a significant increase in the myometrium thickness (GExtr300=25.6±5.0 mm) compared to control (GPropi=5.5±0.5 mm). The effect of this high dose is similar to the estrogen effect (GCee=27.5±7.9 mm). In low doses (10 mg/kg), the effect was similar to control. Isoflavones (GExtr300) induced also an increase in the number of blood vessels (GPropi=3.5±1.6; GExtr300=10.2±3.6 vessels/mm²) and of eosinophils (CPropi=0.15±0.01; GExtr300=4.3±0.9 eosinophils/mm²). These effects were comparable to those produced by Cee treatment in GCee (9.2±1.1 eosinophils/mm²). CONCLUSION: a high-dose treatment with isoflavones (300 mg/kg per day, 21 days) elicited an estrogen-like, highly significant proliferative action on the rat myometrium.
Isoflavones; Estrogens; Myometrium; Experimental study
