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The xenoestrogen bisphenol A (BPA) is commonly ingested by humans. We examined the effects of neonatal exposure to low versus high doses of BPA over the control of estrogen receptor α (ERα) expression in the preoptic area (POA) of prepubertal female rats. Pups received s.c. injections every 48 h of BPA (high dose, 20 mg/kg and low dose, 0.05 mg/kg) or diethylstilbestrol (DES, 0.02 mg/kg) from postnatal day (PND) 1 to PND7 and were killed at PND8 or PND21. Relative expression of ERα transcripts containing alternative 5′-untranslated regions OS, ON, O, OT, and E1 in POA were evaluated by RT-PCR. Methylation status of ERα promoters was determined by bisulfited DNA restriction analysis and ERα protein by immunohistochemistry. In PND8, the high dose of BPA and DES diminished total ERα mRNA levels, mediated by the decreased expression of ERα-O and ERα-OT variants. In contrast, the low dose of BPA augmented total ERα mRNA by increasing the expression of the ERα-E1 variant. In PND21, both BPA doses increased total ERα mRNA by means of the augmented expression of ERα-O and ERα-OT variants. In PND21, the methylation status of the ERα promoters and the circulating levels of estradiol were similar in all experimental groups. At PND8 and PND21, DES and the high dose of BPA decreased, while the low dose of BPA increased ERα protein in the POA. These findings show that neonatal BPA exposure alters the abundance of hypothalamic ERα transcript variants and protein in a dose-dependent manner.
