Continuous Exposure to 2,3,7,8-Tetrachlorodibenzo-P-Dioxin Inhibits the Growth of Surgically Induced Endometriosis in the Ovariectomized Mouse Treated with high Dose Estradiol

The objectives of this study were to evaluate the effects of repeated injection of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) on the growth of endometriosis and the formation of adhesions in the mouse. Sexually mature female B6C3F1 mice (n = 19) were ovariectomized and subcutaneously implanted with a silastic capsule containing estradiol (E2). Uterine tissues in full thickness (I x I mm2, 5 pieces) from the left uterine horn were surgically autotransplanted to 5 different locations in the peritoneal cavity. One week later the animals were randomly assigned to four groups and treated with: vehicle alone (corn oil). 10.50 or 100 ng/kg/day TCDD for 28 days. Two days after last dose a necropsy was performed to measure the diameter of endometrial implants and to score the adhesions. Endometrial implants were harvested for histology and blood was collected for assessment of E2 levels. The diameter of endometrial implants was significantly smaller in the TCDD treated groups compared to the controls (p < 0.05). Survival of endometrial implants, the formation and scores of adhesions, and serum E2 levels were not significantly different among the dosing groups. Histology of implants showed a significant regression of endometrial tissues in the animals receiving 50 and 100 ng/kg/day TCDD compared to the controls. We conclude that continuous exposure to TCDD resulted in regression of the endometriotic implants in the ovariectomized mice treated with a high dose exogenous F2.