Mammary Gland Morphology and Gene Expression Signature of Prepubertal Male and Female Rats Following Exposure to Exogenous Estradiol

In order to properly understand whether xenoestrogens act as estrogens, it is essential to possess a solid portrait of the physiological effects of exogenous estradiol. Because the estrogen-dependent gene expression is one of the primary biomarkers of estrogenic action, we have assessed effects of three doses of exogenous estradiol (0.1, 1.0 and 10 µg/kg of body weight/day) on the mammary gland morphology and gene expression profiles by microarray analysis of prepubertal male and female rats of both sexes compared to untreated controls. Estradiol was administered subcutaneously with minipumps from weaning at PND21 to the end of the experiment at PND33. The data suggest that the male mammary is a sensitive tissue for estrogenicity assessment. Groups of male and female rats were infused subcutaneously with mini-osmotic pumps with 17β-estradiol from weaning on post-natal day (PND) 21 until PND 33. Pumps delivered doses of 0, 0.1, 1.0 and 10 µg/kg/d. At sacrifice (PND 33) abdominal mammary gland pairs were collected and fresh frozen in liquid nitrogen.