RESPONSE OF ADULT MURINE UTERINE EPITHELIUM TO 50-PERCENT METHOXYCHLOR

This study was designed to assess the response of uterine epithelia of adult mice to a 4-week exposure of 50% methoxychlor (MXC) to ascertai n whether significant changes were induced by 50% MXC that might compr omise future implantation. Sexually mature virgin female mice were exp osed to 0.1, 0.5, 1.0, 2.5, or 5.0 mg MXC via oral gavage for 5 consec utive days for 4 weeks. Controls received either sesame oil or 25 mu g estradioi-17 beta (E-17 beta) also by gavage. At sacrifice, segments from each uterine horn were prepared for morphometric studies or for t ransmission electron microscopy. Results revealed a dose-dependent inc rease in the heights of uterine epithelial cells. Epithelial cell heig hts of the two groups treated with the highest doses of the pesticide were similar to that of the E-17 beta-treated group. Electron microsco py revealed increased vacuolization and swelling of mitochondria in ce lls of the 2.5 and 5.0 mg treated groups when compared to either of th e control groups. In addition, there were effects on the number and si ze of microvilli in the uterine epithelial cells. The present study cl early demonstrates that a 4-week exposure of adult female mice to 50% MXC elicits significant estrogenic and toxic effects on the uterine ep ithelium.