Abstract

This study was undertaken with the aim of investigating the teratogenic effects of methylmercury (MeHg) on the chick embryos and evaluating the protective role of vitamin C and folic acid. Fertilized eggs received MeHg dose (2.5 mg/egg) alone or with addition of vitamin C (100 mM) and folic acid (100 mM) or with vitamin C and folic acid alone. Control eggs received saline. The eggs were injected on day zero of incubation. On day five, embryos were examined for viability, gross retardation and gross malformation and the hearts were processed for light and electron microscopy. Results showed that MeHg decreased the survival rate of embryos and caused gross malformations such as hypomorphic hearts, abnormal position of atria, exencephaly, hydrocephaly, anencephaly, everted viscera, microphthalmia, twisted body, limb malformation and hemorrhage, compared with control embryos. Histological examination of the hearts clearly revealed that the heart tissues have failed to develop correctly in the MeHg treated embryos. The corresponding pathological alterations were mainly characterized as cell death at the ultrastructural level. Embryos injected with MeHg plus vitamin C and folic acid were almost comparable to the control. Data obtained in this study suggest that supplementation with vitamin C and folic acid during pregnancy may prevent defects in heart development brought about by MeHg and other environmental xenobiotics.

Key words: Chick embryo, methylmercury, vitamin c, folic acid, teratogenicity.This study was undertaken with the aim of investigating the teratogenic effects of methylmercury (MeHg) on the chick embryos and evaluating the protective role of vitamin C and folic acid. Fertilized eggs received MeHg dose (2.5 mg/egg) alone or with addition of vitamin C (100 mM) and folic acid (100 mM) or with vitamin C and folic acid alone. Control eggs received saline. The eggs were injected on day zero of incubation. On day five, embryos were examined for viability, gross retardation and gross malformation and the hearts were processed for light and electron microscopy. Results showed that MeHg decreased the survival rate of embryos and caused gross malformations such as hypomorphic hearts, abnormal position of atria, exencephaly, hydrocephaly, anencephaly, everted viscera, microphthalmia, twisted body, limb malformation and hemorrhage, compared with control embryos. Histological examination of the hearts clearly revealed that the heart tissues have failed to develop correctly in the MeHg treated embryos. The corresponding pathological alterations were mainly characterized as cell death at the ultrastructural level. Embryos injected with MeHg plus vitamin C and folic acid were almost comparable to the control. Data obtained in this study suggest that supplementation with vitamin C and folic acid during pregnancy may prevent defects in heart development brought about by MeHg and other environmental xenobiotics.

Key words: Chick embryo, methylmercury, vitamin c, folic acid, teratogenicity.