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      Sodium-Dependent Ascorbic and Dehydroascorbic Acid Uptake by SV-40-Transformed Retinal Pigment Epithelial Cells

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          The present data confirmed previous studies with other cell types that ascorbic acid and dehydroascorbic acid are transported through different transporters into SV-40-transformed retinal pigment epithelial cells. These experiments were performed on cells grown on 96-well culture plates. Ascorbic acid was taken up into the cell by a high-affinity transporter with K<sub>m</sub> = 0.041 mmol/l and a low Vmax of 2.74 pmol/min/well. Dehydroascorbic acid was taken up by a low-affinity transporter with K<sub>m</sub> = 5.67 mmol/l; however, the V<sub>max</sub> was 325.5 pmol/min/well. The uptake of both ascorbic acid and dehydroascorbic acid was dependent on the sodium concentration. The uptake of ascorbic acid does not involve oxidation-reaction steps because the uptake of [<sup>14</sup>C]-ascorbate was unaffected by the presence of an excess amount of unlabelled dehydroascorbic acid.

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          Author and article information

          Ophthalmic Res
          Ophthalmic Research
          S. Karger AG
          11 December 2009
          : 25
          : 2
          : 100-107
          aDepartment of Ophthalmology, University of Texas Health Science Center at San Antonio; bBiorhythm Research Laboratory, Division of Mathematics, Computer Science, and Statistics, University of Texas at San Antonio, Tex., USA
          267272 Ophthalmic Res 1993;25:100–107
          © 1993 S. Karger AG, Basel

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          Pages: 8
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