Ascorbate transport and recycling by SH-SY5Y neuroblastoma cells: response to glutamate toxicity.
Neurons maintain relatively high intracellular concentrations of vitamin C, or ascorbic acid. In this work we studied the mechanisms by which neuronal cells in culture transport and maintain ascorbate, as well as how this system responds to oxidant stress induced by glutamate. Cultured SH-SY5Y neuroblastoma cells took up ascorbate, achieving steady-state intracellular concentrations of 6 mM and higher at extracellular concentrations of 200 microM and greater. This gradient was generated by relatively high affinity sodium-dependent ascorbate transport (Km of 113 microM). Ascorbate was also recycled from dehydroascorbate, the reduction of which was dependent on GSH, but not on D-glucose. Glutamate in concentrations up to 2 mM caused an acute concentration-dependent efflux of ascorbate from the cells, which was prevented by the anion channel blocker 4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid. Intracellular ascorbate did not affect radiolabeled glutamate uptake, showing absence of heteroexchange.
May
James M
JM
Department of Medicine, Vanderbilt University School of Medicine, 2220 Pierce Ave., 715 Preston Research Blg, Nashville, TN 37232-6303, USA. james.may@vanderbilt.edu
Li
Liying
L
Hayslett
Kendra
K
Qu
Zhi-chao
ZC
D001205:Ascorbic Acid / Q000378:metabolism*; D001692:Biological Transport; D045744:Cell Line, Tumor; D018698:Glutamic Acid / Q000633:toxicity*; D005978:Glutathione / Q000378:metabolism; D006801:Humans; D009447:Neuroblastoma / Q000378:metabolism* / Q000473:pathology
D018698:Glutamic Acid; D005978:Glutathione; D001205:Ascorbic Acid