Effects of methoxychlor on the reproductive system of the adult female mouse. 1. Gross and histologic observations.

The purpose of this study is to examine the effects of the pesticide methoxychlor (MXC) on the reproductive system of the adult female mouse. Sexually mature (7- to 8-week) virgin female CD-1 mice were exposed to 1.25, 2.5, or 5.0 mg MXC (50% technical grade) via oral gavage for 5 consecutive days each week for either 2 or 4 weeks. Control groups received either 0.025 mg estradiol-17 beta (E-17 beta) or the sesame oil vehicle for the same time period. Vaginal smears were taken daily, and weights were recorded weekly. Twenty-four hours following the final exposure, animals were sacrificed. Ovaries and reproductive tracts were removed and weighed. One ovary from each animal was prepared for light microscopic evaluation. Results revealed a dose dependency of MXC in inducing persistent vaginal estrus (PVE). Ovaries of MXC-exposed and E-17 beta-exposed animals weighed significantly less than the sesame oil controls. In addition, there was an increase in the number of atretic large follicles in the E-17 beta group and in those mice treated with the two highest doses of MXC, indicating a potential reduction in the immediate fertility of the animal. Thus, this commonly employed pesticide appears to mimic closely those effects on the female reproductive system induced by estrogens.