Neonatal Exposure to p-tert-octylphenol Causes Abnormal Expression of Estrogen Receptor α and Subsequent Alteration of Cell Proliferating Activity in the Developing Donryu Rat Uterus:

In the present study, we investigated immunohistochemicall y the time-course alterations in estrogen receptor α (ER) expression and cell proliferating activity in the developing uteri of Donryu rats exposed neonatally to a high dose p-tert-octylphenol (OP), an endocrine disrupting chemical (EDC). OP-treatment (sc injections of 100 mg/kg, every other day from postnatal days 1 to 15) induced an early and enhanced ER expression in the luminal epithelium compared with age-matched controls from postnatal day (PND) 10, and increased proliferating cell nuclear antigen (PCNA) positive cells up to PND21. At PND28, ER expression in the luminal epithelium of the OP-treated group was decreased, in association with decline in the luminal epithelial areas. PND14, the second week of life, is coincident with the normal time for differentiation when the luminal epithelium invaginates into the stroma to form uterine glands. OP-treatment, however, delayed and inhibited gland-formation, and suppressed ER expression in the in...