Influence of organochlorine pesticides on development of mouse embryos in vitro.

The effect of DDT, methoxychlor (MXC), and gamma-hexachlorocyclohexane (gamma HCH) on preimplantation mouse embryos in culture was evaluated by the proportion of eight-cell stage embryos developing to expanded and hatched blastocysts. A concentration of 29 micrograms/mL DDT or gamma HCH led to a complete degeneration of exposed embryos. The addition of 29 micrograms/mL MXC showed blastocyst formation (72.3%), but fewer than half of the blastocysts were intact and only 4.3% hatched from the zona pellucida. A concentration of 14.5 micrograms/mL DDT led to 57.5% blastocyst formation and to 6.8% hatched blastocysts; the same concentration of gamma HCH and MXC showed 66.7 and 95.9% blastocyst formation and 22.9 and 49% hatched blastocysts, respectively. The addition of 7.25 micrograms/mL led to 85.9% (DDT), 77.6% (gamma HCH), and 81% (MXC) blastocysts in total, and to 28.2, 35.5, and 49.4% hatched blastocysts, respectively. Compared with untreated controls, only the 3.625 micrograms/mL concentration for all pesticides showed no significant differences in blastocyst formation and hatching. These results show different toxicity of these three pesticides for the preimplantation mouse embryo in the order MXC < gamma HCH < or = DDT).