Effects of coumestrol on estrogen receptor function and uterine growth in ovariectomized rats.

Isoflavonoids and related compounds such as coumestrol have classically been categorized as phytoestrogens because these environmentally derived substances bind to the estrogen receptor (ER) and increase uterine wet weight in immature rats and mice. Assessment of the binding affinities of isoflavonoids for ER and subsequent effects on uterine growth suggest these compounds are less active estrogens than estradiol and therefore may reduce the risk of developing breast or prostate cancer in humans by preventing estradiol binding to ER. With the renewed interest in the relationships between environmental estrogens and cancer cause and prevention, we assessed the effects of the phytoestrogen coumestrol on uterotropic response in the immature, ovariectomized rat. Our studies demonstrated that in this animal model, coumestrol is an atypical estrogen that does not stimulate uterine cellular hyperplasia. Although acute (subcutaneous injection) or chronic (multiple injection or orally via drinking water) administr...