母鼠低剂量接触甲基汞所致仔鼠学习能力及脑海马超微结构的变化

目的]研究ICR母鼠饮水暴露低剂量氯化甲基汞(MeHgCl)后,仔鼠脑组织的病理组织学变化和脑海马超微结构变化,评价低剂量饮水暴露甲基汞的安全性。方法]ICR孕鼠随机分为对照组、低剂量组和高剂量组,每组各8只,各组于怀孕第6天起,分别自由饮用蒸馏水和氯化甲基汞含量为0.01、0.1mg/L的蒸馏水,直至哺乳期结束。测试各组仔鼠学习能力,观察仔鼠脑组织病理组织学变化及脑海马超微结构变化。结果]在对仔鼠进行学习能力测试的水迷宫实验中,对照组、低剂量组和高剂量组成功率分别为81.67%、59.09%和70.00%,低剂量组和高剂量组成功率显著低于对照组(P<0.05)。低剂量组和高剂量组仔鼠脑组织有明显的病理学改变,随着甲基汞染毒剂量的增加,海马区大锥体细胞、大脑神经元和小脑浦肯野细胞嗜酸性增强。电镜结果显示,低剂量和高剂量组脑海马神经细胞有变性,严重者呈暗细胞表现。结论]实验剂量甲基汞可使仔鼠脑组织发生病理组织学改变,脑海马区超微结构改变,实验剂量甲基汞对于仔代是不安全的。

Learning Disability and Ultrastructural Changes of Hippocampus in Offspring of Maternal Mice Exposed to Low-level Methylmercury

Objective]To study the pathological changes of brain and ultrastructural changes of hippocampus in the offspring of maternal mice exposed to low level of methylmercury,and to estimate the safety of low dose exposure to methylmercury for mice.Methods]The pregnant ICR mice were randomly divided into three groups(control,low-level and high-level group), then fed with 0 mg/l,0.01 mg/l and 0.1 mg/l methylmercury respectively in drinking water from the 6th day of gestation until the end of lactation period.The learning ability and pathological changes of offspring's brain were observed.Results]In water maze,the completion rate of control group,low-level group,and high-level group were 81.67%,59.09%,70.00% respectively, and the completion rate of the intoxicated groups were significantly lower than the control group(P<0.05).Pathological changes of the offspring's brain were visible.Electronic microscopy observation indicated that in exposed groups,nerve cells were metamorphic.Conclusion]Methylmercury in the experiment dose was not safe enough for the offspring of the intoxicated mice.