RESUMO
To determine whether it is the hypothalamic-pituitary axis or the ovary that plays the predominant role in abnormal estrous cycling induction by postnatal exposure to estrogenic compounds, female rats were subcutaneously injected with 100mg/kg p-tert-octylphenol or vehicle for 5 or 15 days after birth (OP-PND5, OP-PND15 or control). Ovaries were exchanged between control and treated groups on PND28. Controls receiving control or OP-PND5 ovaries showed normal cycles within 4 weeks after the exchange, and corpora lutea were detected in transplanted ovaries. Controls receiving OP-PND15 ovaries consistently increased persistent estrus (PE). OP-PND15 rats receiving control or OP-PND15 ovaries immediately descended into PE, and transplanted ovaries were atrophic with cystic follicles, indicating anovulation. OP-PND5 rats receiving control or OP-PND5 ovaries showed early onset of PE after normal cycling. The hypothalamic-pituitary axis is predominant in abnormal cycling induction by postnatal exposure to OP. OP-PND15 ovaries were impaired compared to other groups.