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Dehydroascorbate (DHA) competitively inhibits the uptake of 2-deoxy-D-glucose and of 3-O-methyl-D-glucose by human blood neutrophils; 2-deoxyglucose and 3-O-methylglucose competitively inhibit dehydroascorbate uptake. Ratios of Km to Kl are near unity for each of these ligands. Exposure of cultured human fibroblasts to insulin enhances cytochalasin B-inhibitable uptake of DHA and of 2-deoxyglucose, both to the same degree. These observations suggest that DHA transport is mediated by glucose transport systems in human neutrophils and fibroblasts.

Incubation of human leukocytes with dehydroascorbate (DHA) results in an increase in their reduced ascorbate (AA) content and hexose monophosphate shunt (HMS) activity, independent of oxygen supply. Incubation with AA induces these changes only in the presence of oxygen. The increase in HMS activity observed as cell AA increases by 1 µmol is the same during incubation with either DHA or AA. We propose that human leukocytes take up ascorbate as DHA (AA after oxidation to DHA) and reduce it promptly to AA, and that HMS stimulation upon incubation with either AA or DHA is a result of DHA reduction.

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