Interactions among ascorbate, dehydroascorbate and glucose transport in cultured hippocampal neurons and glia

There is an increasing recognition of the damaging role played by oxygen ra dicals in mediating necrotic neuronal injury. As such, it becomes important to understand the transport mechanisms that help maintain appropriate leve ls of small molecule antioxidants such as ascorbate in the brain. It has lo ng been known that the transport of dehydroascorbate (DHA) into a variety o f cell types is accomplished through the Glut-1 glucose transporter. In thi s paper, we characterize interactions among the transports of ascorbate, DH A and glucose in hippocampal cultures. We find: (a) sodium-dependent transp ort of ascorbate in mixed neuronal/glial, pure glial, and neuron-enriched h ippocampal cultures; in contrast, we observed no such transport of DHA; (b) such ascorbate. transport appeared to be independent of the glucose transp orter, in that glucose did not compete for such transport, and overexpressi on of the Glut-1 glucose transporter did not alter ascorbate uptake; (c) in contrast, ascorbate, at concentrations ranging from 1 to 20 mM inhibited 2 -dexogyglucose transport in mixed, glial and enriched neuronal hippocampal cultures; (d) potentially, ascorbate, by acting as an electron donor, could impair the function of molecules involve in the transport or metabolism of glucose. We observed mild inhibition of glucose transport by one unrelated electron donor (glutathione). Moreover, transport was also inhibited by an ascorbate analog which is not an electron donor. Thus, we conclude that as corbate transport in hippocampal neurons and glia occurs independent of the glucose transporter but that, nevertheless, ascorbate, at concentrations g enerally thought to be supraphysiological, has the potential for disrupting glucose transport. (C) 2001 Published by Elsevier Science B.V.