Abstract: Purpose : Uterot rophic assay has been kown efficient for detecting endocrine disrupters. To examine the est rogenic activity of bisphenol A(BPA) using the immature female SD rat . Methods : The vehicle cont rol(the peanut oil) , positive cont rol (est radiol benzoate , E2B , 0. 4 mg/ kg ) and BPA(200 mg/ kg ,400 mg/ kg and 800 mg/ kg) were given orally for 3 and 7 consecutive days beginning postnatal day 21. Then rat s were sacrificed 24 hour after the last administ ration. Results : Uterine weight , uterine/ weight , the thickness of the myomet rium and the height of the luminal epithelium increased in E2B , BPA 400 mg/ kg and 800 mg/ kg group ( P <0. 01) with a dose2response relationship. Administered BPA for 7 days , the vaginal opening time of the immature female SD rat s advanced. Conclusion : BPA has weak est rogenic activity in SD rat . The hypert rophy andhyperplasia of myomet rial cell of uterus may induce the uterine weight increase.

Key words: uterot rophic assay, bisphenol A, est rogenic activity, immature female SD rat