Effects of early and late treatment with soy isoflavones in the mammary gland of ovariectomized rats.

INTRODUCTION: Soy isoflavones have been shown to be an alternative to hormone therapy at menopause, without causing side-effects such as breast cancer. However, the effects of early and late treatment with isoflavones on the mammary gland remain controversial. OBJECTIVE: To investigate the effects of early and late treatment with soy isoflavones on the mammary gland of ovariectomized rats. METHODS: Thirty 3-month-old rats were ovariectomized and divided equally into groups: Control, treated with vehicle solution; or with 150 mg/kg/body weight of isoflavones by gavage; or subcutaneously treated with 10 µg/kg/body weight with 17ß-estradiol. Treatments started 3 days (early treatment) or 30 days (late treatment) after ovariectomy and lasted for 30 consecutive days. Thereafter, the animals were euthanized and the mammary glands were removed and processed for paraffin embedding. Sections were stained with hematoxylin and eosin for histomorphometry or subjected to immunohistochemical detection of Ki-67 and VEGF-A. RESULTS: The ductal, lobular and total epithelial fractions were similar between controls and the early/late isoflavone groups, but they were significantly higher in the groups treated with estradiol. In both epithelial and stromal regions, the immunoreactivity of VEGF-A and the percentage of Ki-67-positive cells were significantly higher in the groups treated with estradiol, while they were similar in the early/late isoflavone groups and control groups. CONCLUSION: Our results indicate that early and late treatment with soy isoflavones at the dose of 150 mg/kg/body weight does not show proliferative and angiogenic effects on the mammary gland of ovariectomized rats.

Do extracts of oral soybean augment the trophic effect of estrogen on the rat uterus?

OBJECTIVE: To evaluate whether soybean extracts and estrogens present additive effects on adult rat uterus. METHODS: Fifty ovariectomized rats were randomly divided into five equal groups of ten animals: Control, treated with vehicle; SE46 and SE120, treated with 46 and 120 mg/kg soybean concentrated extract (SE), respectively; EE, treated with conjugated equine estrogens (CE) 50 µg/kg; SE120 + EE, treated with 50 µg/kg (CE) plus 120 mg/kg SE. The substances were administered daily by gavage for 21 consecutive days. Thereafter the animals were weighed and killed by decapitation; trunk blood was collected for hormone determinations. Uteri were removed immediately and fixed in 10% formaldehyde, followed by dehydration, embedding in paraffin and 6-m sections staining with hematoxylin and eosin for histomorphometric analyses of myometrium and endometrium. After ANOVA analysis of the data, the study was complemented with the Tukey-Kramer test for multiple comparisons. RESULTS: The concentrated extract of soybean at high concentration (SE 120 kg/mg) and estrogens proved to have a trophic effect on the uterus (endometrium and myometrium) of castrated rats. In groups SE120, EE and SE120 + EE, all morphometric parameters examined (number of glands, eosinophils, blood vessels and the glandular area) were increased. No significant addictive effects of soybean extract plus estrogens were detected in the SE120 + EE group. CONCLUSIONS: Our results indicate that soy extract has a trophic effect on rat uterine structures. Treatment of ovariectomized rats with a concentrated soy extract in combination with conjugated estrogens had no addictive effect on the uterine response.