Scanning electron microscopic study of the effect of chlorpyrifos on the developing neural tube in comparison with Arsenic in mouse embryo

Abstract

Background: Arsenic is an important environmental toxicant which is usually found in drinking water in inorganic form. Arsenic exposure in pregnant mice causes neural tube defects (NTDs). Chlorpyrifos, an organophosphorus insecticide, recommended universally and in Egypt to control various pests, was evaluated for its potential developmental toxicity. Studies have shown increasing evidence to suggest an association between environmental exposure to this agricultural pesticides and adverse reproductive outcomes. The hypothesis tested in this investigation is chlorpyrifos causes significant defects on the developing central nervous system compared to the proven Arsenic.
Objectives: The aim of this work was to assess congenital malformations induced by the organophosphorus insecticide chlorpyrifos on the neural tube and brain development in comparison with the positive control Arsenic.
Methods: Virgin female ICR (CD-1) mice, approximately 10 weeks old were mated with adult males. The day the vaginal plug was found was considered day 0 of gestation. It consisted of 320 mice. They were subdivided into four groups of 80 bred mice each. Each group was divided into 4 subgroups, and 20 mice per each were treated by gavage as follows: 30 mg/kg/day chlorpyrifos (tested group), 40 mg/kg/day sodium Arsenite (positive control group), and corn oil and distilled water (negative control groups) on days 6–15 of gestation. Maternal observations throughout gestation were reported. In each subgroup the mice proved to be pregnant were sacrificed on gestational days; GD 10, 11, 12 and 16. The day of scarification was determined according to the neural tube developmental stages. The conceptus extraction was done and their number reported to be subjected to the SEM study. After mice scarification, the uteri were opened and a total of 30 embryos and fetuses, randomly selected from each subgroup were processed for scanning electron microscopy investigating the neural tube developmental defects.

Results: CPF ingested by gravid mice at dose of 30 mg/kg/day started from 6th day of gestation proved to produce NTDs as compared to Arsenite.
Conclusion: Neural tube defects are due to chlorpyrifos that may directly influence brain cell replication and differentiation.