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 estrogen ic activities in different animals. To determine whether there is synergism between purified MXC and a natural estrogen, ovariectomized adult mice rec eived 3 daily intraperitoneal doses of either 2.5 or 25 ng estradiol-17 bet a 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 polyacryl amide gel to determine albumin content. The remaining uterine horn and vagi na were prepared for histology and epithelial height measurements. Estradio l significantly increased reproductive-tract weights. Although both the vag inal and uterine epithelial heights increased in mice treated with combined chemicals when compared to controls, the organ histology did not show incr eased stimulation. Albumin content was significantly elevated only in the e stradiol group. The present data do not suggest that either synergism or ad ditive effects occurred between an estrogen and MXC in the reproductive tra cts of ovariectomized adult mice. In fact, combining MXC with estradiol sug gests inhibitory effects.