Effects of various phytoestrogens and of Cimicifuga racemosa (CR) in the mammary gland of ovariectomized (ovx) rats

Background

The sales of soy and red clover extracts or thereof purified isoflavones (genistein, daidzein and its metabolite equol) have increased. These substances are known to be estrogenic in the uterus but their effects in the mammary gland are unknown. The CR extract BNO 1055 has no estrogenic effect. An action in the mammary gland was not yet studied. Therefore, we treated ovx rats orally with genistein (15.5mg/day), daidzein (15.8mg/d) and equol (15.8mg/d) and with the CR extract BNO 1055 (30.0mg/d) for a period of 3 months. Control ovx animals received soy free or estradiol 17β (E2) containing food (0.25mg/d).

Morphometric analysis of mammary gland: The mammary glands of negative control animals were atrophic and the few structures consisted mostly of lobuli type II (less than 5 alveoli per lobulus). E2 treatment stimulated mammary gland tissue: The number of lobuli type I and type II (more than 5 alveoli per tubulus) increased significantly (p<0.001) and secretory material was present. Genistein > daidzein > equol stimulated the number of lobuli type I and type II also significantly (p<0.001). No proliferative effect on mammary gland tissue was observed in BNO 1055 treated animals.

It is concluded that genistein > daidzein > equol have not only uterotropic but also significant mammatropic effects whereas the CR extract BNO 1055 is devoid of such estrogenic effects in the mammary gland.