Bisphenol-A differently affects estrogen receptors-alpha in estrous-cycling and lactating female rats

The effect of long-term exposure to bisphenol-A (BPA) on estrogen receptor- alpha (ER) immunoreactivity was studied in the medial preoptic area, arcuat e nucleus and the ventromedial nucleus of the hypothalamus of estrous cycli ng and lactating female rats. Pregnant/lactating or estrous cycling rats we re exposed to BPA (40 mg/Kg/day) or peanut oil. Lactating females showed fe wer ER-immunoreactive cells than non-lactating females in the medial preopt ic area and ventromedial nucleus of the hypothalamus. BPA induced an increa se in ER-immunoreactive cells in the medial preoptic nucleus irrespective o f lactation. BPA only induced a decrease in ER-immunoreactive cells in the arcuate nucleus of the lactating group; oil induced an increase in ER-immun oreactive cells in the lactating with respect to non-lactating group. The r esults demonstrate that exposure of adult females to BPA modifies the numbe r of ERs. (C) 2001 Published by Elsevier Science Ireland Ltd.