Estradiol and pesticide methoxychlor do not exhibit additivity or synergism in the reproductive tract of adult ovariectomized mice

The pesticide methoxychlor (MXC) is a DDT substitute that exhibits estrogenic activities in different animals. To determine whether there is synergism between purified MXC and a natural estrogen, ovariectomized adult mice received 3 daily intraperitoneal doses of either 2.5 or 25 ng estradiol-17beta or 0.125, 0.25, or 0.5 mg MXC administered separately or in combination. The mice were sacrificed on d 4. Reproductive tracts were excised, weighed, and one uterine horn was flushed with phosphate-buffered saline, with the fluid electrophoresed on a one-dimensional sodium dodecyl sulfate polyacrylamide gel to determine albumin content. The remaining uterine horn and vagina were prepared for histology and epithelial height measurements. Estradiol significantly increased reproductive-tract weights. Although both the vaginal and uterine epithelial heights increased in mice treated with combined chemicals when compared to controls, the organ histology did not show increased stimulation. Albumin content was significantly elevated only in the estradiol group. The present data do not suggest that either synergism or additive effects occurred between an estrogen and MXC in the reproductive tracts of ovariectomized adult mice. In fact, combining MXC with estradiol suggests inhibitory effects.