Ascorbate function and metabolism in the human erythrocyte.
Ascorbate function and metabolism in the human erythrocyte.
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DOI：
10.2741/a262
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发表时间：
1998
期刊：
影响因子：
--
通讯作者：
J. M. May
中科院分区：
文献类型：
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作者：
J. M. May
抗坏血酸，即维生素C，是血浆中一种重要的抗氧化剂，它能清除氧自由基，并有助于保护脂蛋白中的α - 生育酚（维生素E）。红细胞作为血液中数量最多的细胞，有助于维持血浆中的抗坏血酸含量。与能大量富集抗坏血酸的有核细胞不同，红细胞中的抗坏血酸浓度与血浆中的相同。然而，红细胞具有很强的能力将其双电子氧化形式——脱氢抗坏血酸（DHA）还原为维生素。DHA通过丰富的葡萄糖转运蛋白GLUT1被这些细胞迅速摄取。细胞内的DHA在直接化学反应中被谷胱甘肽（GSH）迅速还原为抗坏血酸，不过也已证实存在涉及谷氧还蛋白和硫氧还蛋白还原酶的依赖酶的机制。在生理pH值下带负电荷的抗坏血酸缓慢地进出细胞。尽管如此，抗坏血酸从红细胞中缓慢释放既能维持血浆中维生素的浓度，又能防止低密度脂蛋白中的α - 生育酚被氧化。此外，细胞内的抗坏血酸可以节省并可能循环利用红细胞膜中的α - 生育酚。反过来，α - 生育酚保护细胞膜免受脂质过氧化。红细胞循环利用抗坏血酸的能力，以及抗坏血酸保护细胞膜和脂蛋白中α - 生育酚的能力，为预防血管床炎症区域（如与动脉粥样硬化有关的区域）的脂质过氧化损伤提供了一种潜在的重要机制。
Ascorbic acid, or vitamin C, is an important antioxidant in plasma, where it consumes oxygen free radicals and helps to preserve alpha-tocopherol (vitamin E) in lipoproteins. Erythrocytes, as the most plentiful cell in blood, help to preserve ascorbate in the blood plasma. In contrast to nucleated cells, which avidly concentrate ascorbate, the erythrocyte ascorbate concentration is the same as that in plasma. Erythrocytes nonetheless have a high capacity to regenerate the vitamin from its two electron-oxidized form, dehydroascorbic acid (DHA). DHA is rapidly taken up by these cells on the abundant glucose transport protein, GLUT1. Intracellular DHA is rapidly reduced to ascorbate by GSH in a direct chemical reaction, although enzyme-dependent mechanisms involving both glutaredoxin and thioredoxin reductase have also been demonstrated. Ascorbate, which carries a negative charge at physiologic pH, enters and leaves the cells slowly. Nonetheless, this slow release of ascorbate from erythrocytes can preserve both the plasma concentration of the vitamin, and prevent oxidation of alpha-tocopherol in low-density lipoprotein. In addition, intracellular ascorbate can spare and possibly recycle alpha-tocopherol in the erythrocyte membrane. In turn, alpha-tocopherol protects the cell membrane from lipid peroxidation. The ability of erythrocytes to recycle ascorbate, coupled with the ability of ascorbate to protect alpha-tocopherol in the cell membrane and in lipoproteins, provides a potentially important mechanism for preventing lipid peroxidative damage in areas of inflammation in the vascular bed, such as those involved with atherosclerosis.