Perinatal exposure to xenoestrogens impairs mammary gland differentiation and modifies milk composition in Wistar rats

The current study examined the consequences of perinatal (gestation+lactation) exposure to Bisphenol A (BPA) or diethylstilbestrol (DES) on F1 mammary gland (MG) differentiation. BPA (0, 0.7 or 64 μg/kg bw/day) or DES (6 μg/kg bw/day) was administered in the drinking water of F0 rats from gestational day 9 (GD9) until weaning. F1 females were bred, MG samples obtained on GD18 and GD21, and, during lactation, milk yield and milk protein composition were assessed. On GD18, there was a decrease in α-lactalbumin and β-casein levels that was accompanied by reduced prolactin receptor and Stat5a/b expression. On GD21, delayed histological MG differentiation was observed. β-Casein levels remained decreased on GD21 and in milk samples. Moreover, the BPA- and DES-exposed groups had an altered milk yield pattern during lactation. The long-lasting effects of perinatal exposure to low doses of xenoestrogens included delayed MG differentiation, altered milk yield and modified milk composition.