Abstract
Recently, environmental pollution with man-made chemicals having weak estrogenic effects, which may disturb the endocrine systems of wildlife and human beings, has become an important social problem. In particular, effects of perinatal exposure to such endocrine disrupting chemicals (EDCs) are a focus of attention, because of their potential to act as estrogens and influence on the growth and differentiation of organs. In rodents, the reproductive tract undergoes rapid growth and differentiation within the first 2 weeks of postnatal life named 'critical point' or 'a unique window of vulnerability', because this period is very sensitive with regard to exogenous estrogens or androgens. In female mammals, inappropriate neonatal exposure to these hormones is known to induce the serious effects on the reproductive system, called 'androgenization' due to irreversible disruption of the hypothalamo-pituitary-gonadal control system immediately after birth. This paper will be presented effects of neonatal exposure to estrogenic EDCs for different periods on the female reproductive system including uterine carcinogenesis using 2-stage uterine cancer model in Donryu rat. As a result, the neonatal exposure for different periods induced different types of uterine adenocarcinomas, suggesting that two different pathways driven by androgenization or delayed anovulatory syndrome, the latter being incomplete androgenization, dependent upon exposure periods develop the tumors.
