Effect of vitamin E on preovulatory stage irradiated female mouse expressed as chromosomal abnormalities in generated embryos

ABSTRACT

The present study has been carried out to investigate the effects of preovulatory stage gamma-irradiation of female mice in the absence or presence of vitamin E on numerical chromosome abnormalities in 8-cell embryos after mating with nonirradiated males. The 8-11 weeks adult female NMRI mice were whole body irradiated at preovulatory stage [post PMSG injection and about 12-18 hours before injecting HCG] with 4 Gy gamma-rays generated from a cobalt-60 source alone or in combination with 200 IU/kg vitamin E, intraperitoneally administered one hour prior to irradiation. Soon after HCG injection super ovulated irradiated females were mated with non-irradiated males. About 68-h post coitus [p.c], 8-cell embryos were flushed from the oviducts of pregnant mice and were fixed on slides using standard methods in order to screen for metaphase spreads and numerical chromosome abnormalities. In control embryos, 8% of metaphase plates were aneuploid, whereas in preovulatory stage irradiated female mice, about 50% of metaphase plates of embryos showed numerical chromosome aberrations [P<0.001]. Administration of vitamin E one hour before the irradiation reduced chromosomal aberrations significantly [P=0.005]. Results show that the effects of gamma-irradiation on preovulatory stage oocytes led to chromosomal abnormalities in subsequent embryos generated by these oocytes. Increase the frequency of numerical chromosome abnormalities -mostly aneuploidy- may be due to abnormal chromosomal non disjunctions during 2[nd] meiotic division. Reduction of the frequency of chromosome aberrations in the presence of vitamin E is probably due to antioxidant effects of this vitamin, and scavenging free radicals induced by gamma-rays in mice oocytes' environment