Sodium-dependent ascorbic and dehydroascorbic acid uptake by SV-40-transformed retinal pigment epithelial cells.
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 Km = 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 Km = 5.67 mmol/l; however, the Vmax 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 [14C]-ascorbate was unaffected by the presence of an excess amount of unlabelled dehydroascorbic acid.
Lam
K W
KW
Department of Ophthalmology, University of Texas Health Science Center, San Antonio 78284-6230.
Yu
H S
HS
Glickman
R D
RD
Lin
T
T
D001205:Ascorbic Acid / Q000378:metabolism*; D001693:Biological Transport, Active; D002472:Cell Transformation, Viral; D002478:Cells, Cultured; D002851:Chromatography, High Pressure Liquid; D003683:Dehydroascorbic Acid / Q000378:metabolism*; D006801:Humans; D007700:Kinetics; D010084:Oxidation-Reduction; D010857:Pigment Epithelium of Eye / Q000378:metabolism*; D013539:Simian virus 40; D012964:Sodium / Q000378:metabolism*
D012964:Sodium; D001205:Ascorbic Acid; D003683:Dehydroascorbic Acid