Glucose-independent transport of dehydroascorbic acid in human erythrocytes.
It has been previously reported that glucose and its structural analogs inhibit dehydroascorbic acid (DHA) transport across the membranes of nonpolar cells, which led to the suggestion that the hexose transporter mediates dehydroascorbic acid transport. The present study examines the role of the erythrocyte hexose transport system in dehydroascorbic acid uptake. We have confirmed that dehydroascorbic acid may be a ligand of the hexose transport system under certain experimental conditions. However, there is an additional pathway of dehydroascorbic acid transport that is uninfluenced by external glucose. This pathway is one of facilitated diffusion, demonstrating saturation kinetics of transport, cis-inhibition, and trans-stimulation. The Km for the system is 412 microM. It is suggested that this previously undescribed sugar-independent transporter is the physiologically important route of DHA uptake in erythrocytes.
D000328:Adult; D001205:Ascorbic Acid / Q000031:analogs & derivatives*; D003683:Dehydroascorbic Acid / Q000378:metabolism*; D004912:Erythrocytes / Q000378:metabolism*; D005947:Glucose / Q000502:physiology*; D006801:Humans; D013997:Time Factors
D005947:Glucose; D001205:Ascorbic Acid; D003683:Dehydroascorbic Acid