Prenatal Bisphenol A exposure delays the development of the male rat mammary gland

•The male mammary gland is sensitive to endocrine disrupting chemicals.•Whole mounts evidence abnormal development in the BPA-exposed male mammary gland.•Mammary gland development is delayed in BPA-exposed prepubertal male rats.•Androgen receptor expression is decreased in BPA-exposed male mammary gland.

Our aims were to evaluate whether exposure to Bisphenol A (BPA) modifies the development of the male rat mammary gland (MG) and to evaluate whether this modification is gender specific. From gestational day 9, pregnant rats were exposed either subcutaneously to 0, 25 or 250 μg BPA/kgbw/day until parturition or orally to 0 and 64 μg BPA/kgbw/day until weaning. MG development was analyzed on postnatal days (PND) 5, 15 and 30. On PND30, steroid hormone receptor expression and mammary growth were also evaluated. On PND30, the exposure to 64BPA and 250BPA induced a delay in male MG development, evidenced by reduced ductal growth, decreased number of terminal structures and lower expression of androgen receptor (AR). In contrast, female mammary ductal growth was altered only by 250BPA. Regardless of the administration route and length of the exposure period, BPA induced a delay in MG development and modified AR expression in prepubertal male rats.