Abstract
Bisphenol A (BPA) is a synthetic oestrogen that is extensively used in a wide range of daily used plastic products. This makes it one of the environmental chemicals that may have impact on human health. Due to its oestrogenic effect, BPA might affect the mammary gland. This study aimed to investigate the influence of BPA on the histological structure of the mammary gland of the adult female albino rat and its effect on epithelial cell proliferation and apoptosis status, in addition to its possible modulating effect on estrogen receptor expression. Thirty female adult albino rats were divided into control and experimental groups. The rats in the experimental group were gavaged with 5 mg/kg BPA daily for 8 weeks. The mammary glands were dissected and processed for histological and immunohistochemical stains for Ki-67, activated caspase-3 and estrogen receptor alpha (ER-α). BPA induced an increase in the number and size of the acini and ducts in the mammary gland of treated rats with hyperplasia of their lining epithelial cells. The collagen fibre content was significantly increased in the connective tissue stroma separating the ducts. Immunohistochemical results showed a significant increase in Ki-67 and caspase-3, but a non-significant increase in ER-α expression. Bisphenol A induced structural changes and affected the proliferation rate of mammary glands, so it might be one of the predisposing factors for breast cancer.