氯化甲基汞致脑发育损伤形态学研究

Morphological research on injury of brain development induced by methyl mercuric chloride

目的:探讨氯化甲基汞(MMC)致大鼠不同发育阶段脑组织形态结构改变。方法:雌性Wistar大鼠体重(120±20)g,随机分为3个实验组和对照组各30只。3个实验组母鼠从妊娠前90天至仔鼠出生后30天连续喂饲含有不同剂量(0.75、1.50和3.00 mg/kg)MMC的普通饲料,对照组给予普通饲料。脑切片经苏木精-伊红染色,在光镜下观察长期接触低剂量MMC仔鼠脑组织形态结构。采用荧光原位末端标记法,在激光共聚焦显微镜下计数两组生后不同时间点仔鼠大脑、小脑和海马发生凋亡的神经元,以PCD阳性率表示凋亡的多少。结果:在实验设计的接触剂量下,仔鼠大脑、小脑和海马神经元体积缩小、固缩,核染色质致密等凋亡形态特征。实验组和对照组生后不同时间点仔鼠脑神经元都存在凋亡。结论:大鼠长期低剂量接触不同浓度MMC可使其生后仔鼠大脑、小脑和海马部分神经元出现凋亡形态学改变,随仔鼠脑汞含量升高神经元凋亡率明显增加。

Objective： To explore the morphological and structural changes of brain tissues of rats during different developmental stages induced by methyl mercuric chloride （MMC）. Methods ： Female Wistar rats whose body weight was （ 120 ± 20） g were randomly di- vided into three experimental groups and control group, 30 rats in each group. The female rats in the three experimental groups were fed with general fodder containing different doses of MMC （0. 75, 1.50, and 3.00 mg/kg） from 90 days before pregnancy to 30 days after birth of newborn rats. The rats in control group were fed with general fodder. The brain slices were treated with HE staining, the morphology and structure of brain tissue of newborn rats exposure to low - dose MMC for a long time were observed under light microscope. Fluorescence in situ end labeling method was used to count the apoptotic neurons in cerebrum, cerebellum, and hippocampus at different time points in the two groups under laser scanning confocal microscope, the positive rate of PCD was used to indicate the degree of apoptosis. Results： The volumes of cerebrum, cerebellum, and hippocampus of newborn rats were decreased under the designed dose, the morphological characteristics of apoptosis could be observed, such as karyopyknosis, dense nuclear chromation. Apoptosis of brain neurons could be observed in newborn rats at different time points after birth in experimental groups and control group. Conclusion： Exposure to different concentrations of MMC for a long time in female rats can induce morphological change of apoptosis of partial neurons in cerebrum, cerebellum, and hippocampus of newborn rats after birth, the apoptotic rate of neurons is increased significantly with the increasing of brain mercury content in newborn rats.