Southorn P A, Powis G
Department of Anesthesiology, Mayo Clinic, Rochester, MN 55905.
Mayo Clin Proc. 1988 Apr;63(4):381-9. doi: 10.1016/s0025-6196(12)64861-7.
Free radicals are reactive chemical species that differ from other compounds in that they have unpaired electrons in their outer orbitals. They are capable of damaging cellular components, and accumulating evidence suggests they may contribute to various disease entities. Biologic systems are exposed to free radicals that have been formed endogenously or that result from external influences such as ionizing radiation. Oxygen free radicals are continuously being produced intracellularly by oxidation-reduction reactions. The sequential univalent reduction of molecular oxygen initially forms the superoxide anion radical, which in turn is converted, in the presence of transition metal ions, into the highly reactive hydroxyl radical. Free radicals are detected by electron spin resonance spectroscopy, but often this procedure is difficult to use for study of free radical involvement in biologic systems, and investigators have resorted to inferring their presence by identifying the products of free radical reactions. All aerobic organisms possess substances that help prevent free radical-mediated injury. These include antioxidants such as vitamin E and the enzymes superoxide dismutase and glutathione peroxidase. A second part of this review will describe the role of free radicals in specific disease entities.
自由基是具有反应活性的化学物质，与其他化合物不同的是，它们在外层轨道上有未配对的电子。它们能够破坏细胞成分，越来越多的证据表明它们可能与各种疾病有关。生物系统会接触到内源性形成的或由外部影响（如电离辐射）产生的自由基。细胞内通过氧化还原反应不断产生氧自由基。分子氧的顺序单价还原最初形成超氧阴离子自由基，在过渡金属离子存在的情况下，超氧阴离子自由基又会转化为高反应性的羟基自由基。自由基可通过电子自旋共振光谱法检测，但通常该方法难以用于研究自由基在生物系统中的作用，研究人员只能通过识别自由基反应的产物来推断它们的存在。所有需氧生物都拥有有助于预防自由基介导损伤的物质。这些物质包括抗氧化剂，如维生素E以及超氧化物歧化酶和谷胱甘肽过氧化物酶等酶。本综述的第二部分将描述自由基在特定疾病中的作用。
