13C NMR evidence of the failure of human erythrocytes to metabolize ascorbate and dehydroascorbate to lactate.

13C-NMR spectroscopy was used to record time courses of the metabolism of [1-(13)C]-L-ascorbic acid (AA) and [2-(13)C]-L-ascorbic acid and their dehydro-counterparts (DHAA) by human erythrocytes. Under a range of experimental conditions, but most notably in the absence of glucose in the incubation medium, no (13)C-NMR signal for lactate emerged during any of the 5 h time courses. The NMR resonances that did emerge over time were assigned to diketogulonic (DKG) acid and CO(2). Only very minor resonances from degradation products of DKG appeared from samples that contained physiologically high concentrations of DHAA. These results are in contrast with those in a recent report that lactate is derived from AA in human erythrocytes. However, an explanation for this possible artifact is given.