Dehydroascorbate tissue uptake

The oxidative product of ascorbic acid, dehydroascorbic acid, is the preferred form of the vitamin for uptake by neutrophils, erythrocytes, and lymphocytes (27). Once within the erythrocyte, dehydroascorbic acid is reduced to ascorbic acid by a glutathione-dependent, dehydro-ascorbic-acid-reducing enzyme (20,28). However, the reduced form of ascorbic acid is found in most other tissues, that is, liver, lungs, kidneys, skin, and pituitary and adrenal glands (20,29). From these studies, ascorbic acid is taken up by several tissues by an energy-dependent and Na -sensitive process, but the transport of the oxidized vitamin form follows the principles of diflFusion. 

It has been stated that if 6-hydroxydopamine and 6-aminodopamine are to be selective in their neurotoxic behavior the damaging process must occur intraneuronally following uptake and hence concentration of the neurotoxin within the neuron. In vivo electrochemical measurements have shown that about 20% of 6-hydroxydopamine is converted to its p-quinone within a few minutes after injection into rat brain. " The redox equilibrium between 6-hydroxydopamine and its p-quinone or 6-aminodopamine and its p-quinoneimine is apparently maintained by an active redox buffer, probably ascorbate-dehydroascorbate, which exists in brain tissue. The potential of this redox buffer is apparently close to -0.200 V vs. SCE. 

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