Zheng H, Liu J, Liu Y, Klaassen C D
Department of Pharmacology, Toxicology and Therapeutics, University of Kansas Medical Center, Kansas City, KS 66160-7417, USA.
Toxicol Lett. 1996 Oct;87(2-3):139-45. doi: 10.1016/0378-4274(96)03770-8.
Metallothionein (MT) has been proposed to play an important role in heavy metal detoxication and in the scavenging of free radicals. Effects of MT on the cytotoxicity of cadmium (Cd), tert-butylhydroperoxide (t-BHP) and N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) were examined using primary hepatocyte cultures from control (C57BL/6J) and MT-I and II knock-out (MT-null) mice. Compared to control hepatocytes, MT-null hepatocytes had minimal Cd-binding proteins (MT equivalents), but cellular glutathione concentration was similar to the control hepatocytes. MT-null hepatocytes were more sensitive than controls to the cytotoxic effects of Cd (50-300 microM) and t-BHP (125-500 microM), as indicated by the levels of lactate dehydrogenase released into the medium. Cd and t-BHP also produced more lipid peroxidation in MT-null hepatocytes than in control cells, as demonstrated by the abundance of thiobarbituric acid-reactive substances. However, MT-null hepatocytes were equally sensitive as controls to the cytotoxicity of MNNG (0.5-2.0 mM), suggesting that MT does not protect against MNNG-induced cytotoxicity. These results support the hypothesis that constitutive MT levels affect the sensitivity of mammalian cells to Cd and oxidative stress.
金属硫蛋白（MT）被认为在重金属解毒和自由基清除中发挥重要作用。使用来自对照（C57BL/6J）小鼠以及MT-I和II基因敲除（MT缺失）小鼠的原代肝细胞培养物，研究了MT对镉（Cd）、叔丁基过氧化氢（t-BHP）和N-甲基-N'-硝基-N-亚硝基胍（MNNG）细胞毒性的影响。与对照肝细胞相比，MT缺失的肝细胞具有极少的镉结合蛋白（MT等效物），但其细胞内谷胱甘肽浓度与对照肝细胞相似。如培养基中释放的乳酸脱氢酶水平所示，MT缺失的肝细胞对Cd（50 - 300 microM）和t-BHP（125 - 500 microM）的细胞毒性比对照肝细胞更敏感。如硫代巴比妥酸反应性物质的含量所示，Cd和t-BHP在MT缺失的肝细胞中也比在对照细胞中产生更多的脂质过氧化。然而，MT缺失的肝细胞对MNNG（0.5 - 2.0 mM）的细胞毒性与对照肝细胞同样敏感，这表明MT不能保护细胞免受MNNG诱导的细胞毒性。这些结果支持了组成型MT水平影响哺乳动物细胞对Cd和氧化应激敏感性的假说。
