Analysis of cytogenetic and developmental effects on pre-implantation, mid-gestation and near-term mouse embryos after treatment with trichlorfon during zygote stage

Trichlorfon has been widely used in agriculture as a broad spectrum insecticide. We examined cytogenetic and developmental effects on early mouse zygotes exposed to trichlorfon in vivo. Pregnant female mice were intraperitoneally administered a single dose of trichlorfon (100 or 200mg/kg) at 6h post presumed conception and either sacrificed on day of gestation (dg) 3, 9 or 17 to assess the developmental toxicity and mutagenic effects on embryos.Mean cell number (dg 3) and somite number (dg 9) of embryos in the two trichlorfon-treated groups were significantly fewer than in the control group and the mean micronucleus (MN) number (dg 3) and the frequency of mosaic aneuploidies including monosomic or trisomic cell lines (dg 9) was significantly increased in both trichlorfon-treated groups compared with the control group. However, there was no difference in fetal body weight (dg 17) between the control and trichlorfon-treated groups and no increased incidence of external malformations was observed in the trichlorfon-treated groups. These findings suggest that acute exposure of trichlorfon around fertilization induces a high frequency of MN, mosaic aneuploidies and developmental retardation in pre-implantation and mid-gestation embryos, and thereafter these embryos with MN or chromosome damage appear to develop past mid-gestation and catch up with normal embryos by near-term.