Effects of dioxin, an environmental pollutant, on mouse blastocyst development and apoptosis

Objective: To evaluate the effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin ( TCDD; dioxin) on mouse embryo development and apoptosis. Design: Controlled animal study. Setting: Academic research environment. Animal(s): Female mice (CB6F1) at 3 to 6 weeks of age and proven breeders ( C578B46). Intervention(s): Mouse embryos were obtained at the morula stage and cultur ed to the blastocyst stage in a pharmacologic dose of TCDD (3.1 muM) or a c ontrol medium. The morphology was assessed, and staining for apoptosis was performed. Immunohistochemistry for the presence of aromatic hydrocarbon re ceptor (AhR) was performed in another set of morula-stage embryos. Main Outcome Measure(s): The number of embryos developing from the morula t o the blastocyst stage and number of apoptotic blastomeres in control vs. T CDD culture conditions. Result(s): No statistically significant differences were observed in the pe rcentage of embryos reaching the blastocyst stage: 80.9% (115 of 142) in th e TCDD-treated group, vs. 82.9% (121 of 146) in the control group. There wa s also no difference in the degree of apoptosis: 22.6 +/- 7.3% apoptotic ce lls (TCDD) vs. 25.3 +/- 9.7% (controls). Staining indicated the slight pres ence of aromatic hydrocarbon receptor in the morula-stage mouse embryos. Conclusion(s): TCDD at 3.1 muM did not alter the development of early mouse morula to blastocysts and did not significantly induce apoptosis in vitro. (Fertil Steril(R) 2001,75.1159-62. (C) 2001 by American Society for Reprod uctive Medicine.).