六价铬对大鼠学习记忆的影响

Effect of chromium exposure on rats' learning and memory ability

摘要:

目的 观察六价铬[Cr(VI)] 对大鼠学习记忆的影响。方法 母鼠哺乳期分别给予双蒸水（对照组）、 低（0.8 mg/kg）、中（4.0 mg/kg）、高（20 mg/kg）重铬酸钾溶液（低、中、高剂量重铬酸钾组）。断乳后仔鼠 灌胃与其母鼠相同剂量的重铬酸钾溶液，共6 个月。石墨炉原子吸收光谱法测定大鼠脑组织中铬含量；Morris 水迷宫实验测试大鼠学习记忆能力；尼氏染色和免疫组织化学等方法观察大鼠海马神经细胞及星形胶质细胞 的形态学改变；高效液相色谱法测定谷胱甘肽（GSH）含量。结果 低、中、高剂量重铬酸钾组脑组织中铬 含量与对照组比较，差异有统计学意义（P <0.05）。随着染毒剂量增加，大鼠平均逃避潜伏期和第1 次寻找平 台的潜伏期延长，穿越原平台次数减少，在原平台象限停留时间缩短（P <0.05）。与对照组比较，重铬酸钾组大 鼠海马组织出现损伤、神经元排列紊乱及细胞核浓染固缩。星形胶质细胞GFAP 阳性表达现象随剂量的增加 而加重。与对照组比较，铬暴露组大鼠海马组织的GSH 含量下降（P <0.05）。结论 重铬酸钾可引起大鼠海 马神经元结构及其功能损伤，学习记忆能力降低，其机制可能与Cr（VI）所诱导的氧化应激有关。

Abstract:

Objective To investigate the effects of chromium exposure on learning and memory in rat model. Methods The rats were fed with distilled water (control group) or different concentrations of potassium bichromate solution (0.8, 4.0, 20.0 mg/kg) during lactation period. After weaning, the offspring rats were directly fed with the solutions the same as their mother rats for 6 months. The content of chromium in cerebral tissue were determined with the graphite furnace atomic absorption spectrophotometer. Learning and memory abihties of rats were tested by the Morris water maze experiment. The Nissl staining and immunohistochemical assay were performed to observe the morphological changes of the rat hippocampal nerve cells and astrocytes. High performance liquid chromatography was utilized to determine the content of glutathione (GSH). Results Chromium content in cerebral tissue of rats receiving various concentrations of potassium dichromate increased significantly compared with control group (P < 0.05). The time of passing through the platform and staying around the platform in potassium dichromate exposure group were prolonged compared with control group. With the increase of exposure dose, The average latency and latency to first entry were increased while number of animals crossing original platform and time of stay in the primary quadrant were decreased in dose dependent manner in exposure group when compared with those in control group (P < 0.05). Compared with the control group, potassium bichromateinduced hippocampus damage including disordered neurons, and concentrated and contracted nucleus. Expression of GFAP in astrocytes increased while GSH content in hippocampus tissue decreased in exposure group in dose dependent manner when compared with control group (P < 0.05). Conclusion Exposure to chromium causes disfunction of hippocampal neurons, compromising learning and memory ability.