Effects of methylmercury chloride on the brain chromatin structure in rats at various developing stages

Pregnant rats were injected peritoneally with methylmercury chloride of dosage of 2mg/kg sequently from 7th-11th day after gestation (organogenetic period). Brain nuclei of natal rats at various developing stages were separated and purified with Hewish-Burgoyne method. The effects of methylmercury chloride on brain chromatin structure of natal rats in different developing period were studied. Brain nuclei of rats exposed or unexposed to methylmercury chloride were digested by DNase 1 or EcoR 1, and then nick translation was performed. The amount of ~(3)H-dAMP incorporation into the nuclei of rats from exposed group of 3-day old was significantly lower than that of the unexposed group of 3-day old (P<0.05). We believed that the effects of methylmercury chloride on chromatin structure of the brain nuclei at different developing stages might be closely related to sensitivity of the fetal and infant rats to neurotoxicity of methylmercury chloride.