Estrogenic chemicals at puberty change ERα in the hypothalamus of male and female rats

The effects of two environmental endocrine disruptors, the synthetic pharmaceutical estrogen 17-ethinylestradiol (EE) and bisphenol-A (BPA), were analysed in male and female rats in a very sensitive developmental period, puberty. Immunohistochemistry was used to evaluate changes in the number of cells expressing estrogen receptors (ER-α) in the arcuate nucleus (ARC), ventromedial nucleus (VMH) and medial preoptic area (MPA) of the hypothalamus. Animals were treated during early puberty, from PND 23 to PND 30, with EE and BPA given orally every day. They were then sacrificed and perfused on PND 37 or PND 90, and blood and brains were collected for hormonal determination (testosterone and estradiol) and immunohistochemistry (estrogen receptors, ER). At PND 37, ER-labelled neurons were higher in males than in females in the ARC and MPA. EE and BPA increased ER-labelled neurons in the ARC and MPA. At PND 90, females showed higher ER-labelled neurons in the VMH. EE and BPA increased ER-labelled neurons in the MPA in females. EE increased testosterone in males at PND 37 and estradiol in females at PND 90. These results indicate the ability of estrogenic chemicals to change the reproductive neural circuits during puberty in male and female rats.