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 cultured to the blastocyst stage in a pharmacologic dose of TCDD (3.1 microM) or a control medium. The morphology was assessed, and staining for apoptosis was performed. Immunohistochemistry for the presence of aromatic hydrocarbon receptor (AhR) was performed in another set of morula-stage embryos.

MAIN OUTCOME MEASURE(S): The number of embryos developing from the morula to the blastocyst stage and number of apoptotic blastomeres in control vs. TCDD culture conditions.

RESULT(S): No statistically significant differences were observed in the percentage of embryos reaching the blastocyst stage: 80.9% (115 of 142) in the TCDD-treated group, vs. 82.9% (121 of 146) in the control group. There was also no difference in the degree of apoptosis: 22.6 +/- 7.3% apoptotic cells (TCDD) vs. 25.3 +/- 9.7% (controls). Staining indicated the slight presence of aromatic hydrocarbon receptor in the morula-stage mouse embryos.

CONCLUSION(S): TCDD at 3.1 microM did not alter the development of early mouse morula to blastocysts and did not significantly induce apoptosis in vitro.