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目的研究甲基汞暴露对不同发育期大鼠学习记忆能力的影响及氧化损伤作用。方法对出生后不同时期(PND7、PND14、PND28、PND60)大鼠连续7 d氯化甲基汞(MMC)染毒,正常饲养至成年(69d)进行水迷宫测试,观察其学习记忆改变。水迷宫测试后取大鼠脑组织,用原子荧光光度计和试剂盒分别检测脑组织汞含量、超氧化物歧化酶(SOD)、谷胱甘肽超氧化物酶(GSH-Px)及一氧化氮合酶(NOS)活性。结果 PND60染毒亚组海马组织汞含量明显高于对照组(P<0.01),PND28和PND60染毒亚组皮层组织汞含量均明显高于对照组(P<0.01);空间学习能力测试结果显示,PND7、PND14染毒亚组大鼠水迷宫测试潜伏期差明显长于对照组(P<0.01);PND7、PND14和PND28染毒亚组海马组织SOD活性明显低于对照组(P<0.01),PND7和PND14染毒亚组皮层组织SOD活性明显低于对照组(P<0.01);PND14、PND60染毒组海马组织GSH-Px活性明显低于对照组(P<0.01),各染毒亚组皮层组织GSH-Px活性活性明显低于对照组(P<0.01);PND7、PND14和PND28染毒亚组海马组织NOS活性均明显低于对照组(P<0.01),各染毒亚组皮层组织NOS活性均明显高于对照组(P<0.01)。结论出生后第一和第二周接触甲基汞对大脑学习记忆功能有明显影响,且这种损伤具有不可逆性,其损伤可能与脑组织内还原性酶类活性下降有关。
Objective To investigate the effects of methylmercury exposure on learning and memory ability and oxidative damage in rats of different developmental stages. Methods Rats of different postnatal periods (PND7, PND14, PND28 and PND60) were exposed to Methylmercium Chloride (MMC) for 7 days. Normal rats were fed until the age of 69 days for water maze test, and their learning and memory abilities were observed. After the water maze test, the brain tissue of rats was taken out, and the content of mercury, superoxide dismutase (SOD), glutathione superoxidase (GSH-Px) and monoxide Nitrogen synthase (NOS) activity. Results The content of mercury in the hippocampus of PND60-treated subgroup was significantly higher than that in the control group (P <0.01). The contents of mercury in cortex of PND28 and PND60 subgroups were significantly higher than those in the control group (P <0.01) (P <0.01). The activity of SOD in hippocampus in PND7, PND14 and PND28 subgroups was significantly lower than that in control group (P <0.01), PND7 and PND14 (P <0.01). The activity of GSH-Px in the hippocampus of PND14 and PND60 groups was significantly lower than that in the control group (P <0.01) The activity of GSH-Px was significantly lower than that of the control group (P <0.01). The activity of NOS in hippocampus of PND7, PND14 and PND28 subgroups was significantly lower than that of the control group (P <0.01) Activity were significantly higher than the control group (P <0.01). Conclusions Exposure to methylmercury in the first and second weeks after birth has a significant effect on learning and memory of the brain, and this injury is irreversible. The injury may be related to the decrease of reductase activity in the brain tissue.