Martins E A, Mori L, Birnboim H C, Meneghini R
Department of Biochemistry, University of Sao Paulo, Brazil.
Mol Cell Biochem. 1992 Dec 16;118(2):181-9. doi: 10.1007/BF00299397.
We have investigated the antioxidant properties of V79 Chinese hamster cells rendered resistant to menadione by chronic exposure to increasing concentrations of this quinone. MD1, a clone of resistant cells, was compared to the parental M8 cells; the former showed increased activity of catalase (3 fold), glutathione peroxidase (1.6 fold) and DT-diaphorase (2.6 fold), as well as an increase in glutathione (3.2 fold). Although one of the products of menadione metabolism is superoxide anion, no changes in total superoxide dismutase activity was observed in MD1 cells. MD1 menadione resistant cells were also resistant to killing by hydrogen peroxide and contained tandem duplication of chromosome 6. A similar duplication of chromosome 6 was seen in several independently derived menadione resistant clones and therefore seems closed linked to the establishment of the resistance. Upon removal of menadione from the medium, some of these properties of MD1 cells, viz., resistance to menadione, elevated glutathione levels, and glutathione peroxidase activity, were lost and the cells resembled M8 cells. However, resistance to H2O2, elevated catalase activity and the duplicated chromosome remained stable for more than 40 cell passages in the absence of menadione. The increase in catalase activity was correlated with an increase in catalase mRNA content and a 50% amplification of catalase gene, as determined, respectively, by Northern and Southern blot analysis. The role of the chromosome 6 duplication in resistance to oxidative stress remains to be established. It is not responsible directly for elevated catalase levels since the catalase gene is on chromosome 3.
我们研究了通过长期暴露于浓度递增的甲萘醌而对其产生抗性的V79中国仓鼠细胞的抗氧化特性。将抗性细胞克隆MD1与亲本M8细胞进行比较；前者过氧化氢酶活性增加（3倍）、谷胱甘肽过氧化物酶活性增加（1.6倍）和DT-黄递酶活性增加（2.6倍），同时谷胱甘肽含量也增加（3.2倍）。虽然甲萘醌代谢产物之一是超氧阴离子，但在MD1细胞中未观察到总超氧化物歧化酶活性有变化。MD1甲萘醌抗性细胞对过氧化氢杀伤也具有抗性，并且含有6号染色体的串联重复。在几个独立衍生的甲萘醌抗性克隆中也观察到了类似的6号染色体重复，因此似乎与抗性的建立紧密相关。从培养基中去除甲萘醌后，MD1细胞的一些特性，即对甲萘醌的抗性、谷胱甘肽水平升高和谷胱甘肽过氧化物酶活性丧失，细胞类似于M8细胞。然而，在没有甲萘醌的情况下，对H2O2的抗性、过氧化氢酶活性升高和重复的染色体在超过40次细胞传代中仍保持稳定。通过Northern印迹和Southern印迹分析分别确定，过氧化氢酶活性的增加与过氧化氢酶mRNA含量的增加以及过氧化氢酶基因50%的扩增相关。6号染色体重复在抗氧化应激中的作用尚待确定。它不是过氧化氢酶水平升高的直接原因，因为过氧化氢酶基因位于3号染色体上。
