Mitochondrial Injury as the Mechanism of Paraquat Toxicity

在体外，人们普遍认为NADPH-细胞色素C还原系统在NADPH存在的情况下还原百草枯，因此微体部分(对应于内质网)是毒性机制的细胞内部位。相反，我们证明内质网状系统可能在百草枯的解毒作用中起作用。百草枯不改变体内内质网结构，但仅损伤肺、肝线粒体和培养的肺泡II型细胞。体外培养的大鼠肝线粒体在百草枯和NADH存在下肿胀和破坏，并被超氧化物歧化酶、细胞色素C或对苯二酚保护。用电子细胞化学技术证明了百草枯依赖的自由基产生部位的亚细胞定位。过氧化氢酶、细胞色素c、超氧化物歧化酶和对苯二酚抑制线粒体外膜超氧化物歧化或过氧化氢的产生，经DEAE层析、凝胶过滤和CM层析，从大鼠肝线粒体内分离出一种表达52kD单一多肽的NADH-百草枯还原酶。该多肽对鱼藤酮不敏感，在百草枯和NADH存在下产生超氧阴离子。

In has generally been believed that NADPH-cytochrome c reductase systems reduce paraquat in the presence of NADPH in vitro, and therefore the microsomal fractions (correponding to the endoplasmic reticulum) are the intracellular site of the toxic mechanism. Contraversely, we deonstrated that the endoplasmic reticular systems may play a role in the detoxication of paraquat. Paraquat did not alter the endoplasmic reticulum structure in vivo but damaged mitochondria alone of the lung and liver, and of cultured alveolar type II cells.Isolated rat liver mitochodnria were swollen and destructed in the presence of paraquat and NADH,and protected by SOD,cytochorme c or p-benzoquinone. Electron-cytochemical techniques were used to demonstrate the subcellular location of paraquat-dependent free radical production sites. The production of superoxide or hydrogen peroxide was restricted to the outer mitochondrial membrane and inhibited by catalase, cytochrome c, SOD and p-benzoquinone."NADH-paraquat reductase" repesenting 52 kD single polypeptide was ioslated from the rat liver mitochndoria through DEAE chromatography, gel filtration and CM chromatography. This peptide was insensitive to rotenone and produced superoxide anions in the presence of paraquat and NADH.