Vera J C, Rivas C I, Fischbarg J, Golde D W
Program in Molecular Pharmacology and Therapeutics, Memorial Sloan-Kettering Cancer Center, New York, New York 10021.
Nature. 1993 Jul 1;364(6432):79-82. doi: 10.1038/364079a0.
Although vitamin C is critical to human physiology, it is not clear how it is taken up into cells. The kinetics of cell and tissue accumulation of ascorbic acid in vitro indicate that the process is mediated by specific transporters at the cell membrane. Some experimental observations have linked the transport of ascorbic acid with hexose transport systems in mammalian cells, although no clear information is available regarding the specific role(s) of these transporters, if any, in this process. Here we use the Xenopus laevis oocyte expression system to show that the mammalian facilitative hexose transporters are efficient transporters of the oxidized form of vitamin C (dehydroascorbic acid). Two transport pathways, one with low affinity and one with high affinity for dehydroascorbic acid, were found in oocytes expressing the mammalian transporters, and these oocytes accumulated vitamin C against a concentration gradient when supplied with dehydroascorbic acid. We obtained similar results in experiments using normal human neutrophils. These observations indicate that mammalian facilitative hexose transporters are a physiologically significant pathway for the uptake and accumulation of vitamin C by cells, and suggest a mechanism for the accumulation of ascorbic acid against a concentration gradient.
尽管维生素C对人体生理至关重要，但尚不清楚它是如何进入细胞的。体外抗坏血酸在细胞和组织中的积累动力学表明，该过程由细胞膜上的特定转运蛋白介导。一些实验观察结果将抗坏血酸的转运与哺乳动物细胞中的己糖转运系统联系起来，尽管关于这些转运蛋白在此过程中（如果有）的具体作用尚无明确信息。在此，我们利用非洲爪蟾卵母细胞表达系统表明，哺乳动物易化型己糖转运蛋白是维生素C氧化形式（脱氢抗坏血酸）的有效转运蛋白。在表达哺乳动物转运蛋白的卵母细胞中发现了两条对脱氢抗坏血酸具有低亲和力和高亲和力的转运途径，并且当提供脱氢抗坏血酸时，这些卵母细胞会逆浓度梯度积累维生素C。我们在使用正常人中性粒细胞的实验中也得到了类似结果。这些观察结果表明，哺乳动物易化型己糖转运蛋白是细胞摄取和积累维生素C的一条具有生理意义的途径，并提示了抗坏血酸逆浓度梯度积累的机制。
