出生前后甲基汞暴露对幼鼠海马和小脑结构的影响

Effects of perinatal exposure to methylmercury on the structure of hippocampus and cerebellum in young rats

目的评价出生前后低水平甲基汞暴露对幼鼠海马和小脑结构的影响。方法将SD孕鼠随机分为Ⅰ、Ⅱ和Ⅲ组。Ⅰ组为对照组,自由饮用蒸馏水;Ⅱ、Ⅲ组自孕7天至哺乳期末饮水中分别加入0·1和1mg/(kg·d)甲基汞。观察各组幼鼠早期生理发育指标,21天时取其海马和小脑组织观察结构变化情况。结果各组幼鼠无明显形态和早期生理发育指标的异常改变,21日龄时汞暴露组幼鼠体重低于对照组。光镜下Ⅲ组海马和小脑有个别神经细胞固缩改变,海马结构排列紊乱,Ⅱ组无明显病理改变。免疫组化方法分析阳性表达率,海马NFⅢ组和Ⅱ组低于Ⅰ组(F=7·94,P<0·01);海马GFAPⅢ组和Ⅱ组高于Ⅰ组(F=10·10,P<0·01);小脑NFⅢ组小于Ⅰ组和Ⅱ组(F=6·85,P<0·05);小脑GFAPⅢ组大于Ⅰ组和Ⅱ组(F=4·98,P<0·05)。电镜下观察到Ⅱ组和Ⅲ组均有超微结构改变,如神经元核不规则、胞体固缩、线粒体变性、突起溶解等。结论出生前后低水平甲基汞暴露影响了小脑和海马的超微结构和神经细胞表达。

Objective To evaluate the effects of perinatal exposure to methylmercury on the structure of hippocampus and cerebellum in young pups. Methods Divided the 9 pregnant SD rats into three groups randomly ： group Ⅰ, Ⅱ and Ⅲ . After exposing the rats of the three groups from day 7 in pregnancy through lactation with methylmercury （the dose were 0, 0.1 and lmg/（kg·d） respectively）, examined the early physiology development and the structure of hippocampus and cerebellum of day-21-offspring rats. Results Except for changes in body weight on 21 day, the offspring showed no apparent changes in appearance and physiology, Pyknosis in several neurons and disturbance arrangement of pyramidal cells in CA3 and CA4 region of the hippocampus were observed in hippocampus and cerebellum of the rats in group Ⅲ under the microscope, while no pathological changes were observed in group Ⅱ. Testing the positive expression of immunohistochemistry, we found out that the NF expression of hippocampus in Ⅱ and Ⅲ groups were lower than group Ⅰ （F = 7.94, P 〈 0.01）, while that of GFAP were increased significanlty （ F = 10.10, P 〈 0.01 ）. NF expression of cerebellum in group Ⅲ was lower than group Ⅱ and group Ⅰ （ F = 6.85, P 〈 0.05）. while that of GFAP was higher than the other two groups（ F = 6.85, P 〈 0.05）. The uhrastructure changes happened in both H and m groups examined through electron microscope, including irregular form in nucleus of neurons, pyknosis of soma, degeneration of mitochondria, lysis of dendrite and axon, et al. Conclusion Perinatal low-level methylmercury exposure affected the tdtrastructure and expressions of the neural cells in cerebellum and hippocampus of the young rats.