Modulatory influence of prepubertal biochanin A exposure on mammary gland differentiation and expression of estrogen receptor‐α and apoptotic proteins

Abstract

The modulatory influence of the phytoestrogen biochanin A, an isoflavinoid found in red clover (Trifolium pratense), on the differentiation and proliferation of mammary epithelial cells and the expression of estrogen receptor-alpha (ER-alpha) in female prepubertal Sprague-Dawley rat mammary glands was examined, for which there have been no reports to date. Biochanin A (500 microg/g bw) was injected subcutaneously on days 16, 18 and 20 post-partum. The mammary gland was dissected out and terminal end buds, terminal ducts and lobules were counted. ER-alpha, Bcl2, Bax and caspase-3 expression were determined by immunohistochemistry. Estradiol benzoate (EB) (500 ng/g bw) and dimethyl sulphoxide (DMSO) were used as the reference and vehicle, respectively. The results showed a significant enhancement of differentiation at post-natal day (PND) 21 as well as at PND 50 in the mammary glands. There was a significant decrease of ER-alpha expression at PND 21 and an increased expression of the same at PND 50, whereas increased proliferation at PND 21 and increased apoptosis at PND 50 in the mammary glands were observed in biochanin A treated animals. The mode and magnitude of the effect of biochanin A was almost similar to that of EB. These findings suggested that prepubertal exposure to biochanin A modulated the regulatory processes and in turn enhanced the differentiation and development of mammary glands in female rats. These observations may have significance in human health.