ELEVATED LEVELS OF GLUCOSE AND L-FUCOSE REDUCE NA22-CELL NA+ CURRENT IN CULTURED NEUROBLASTOMA-CELLS( UPTAKE AND WHOLE)

Na+ flux was studied in cultured neuroblastoma cells grown in medium c ontaining increased glucose or L-fucose concentrations. Chronic exposu re of neuroblastoma cells to 30 mM glucose or 30 mn L-fucose caused a decrease in ouabain-sensitive and veratridine-stimulated Na-22(+) upta ke compared with cells cultured in unsupplemented medium. The Na+ curr ent, determined by using whole-cell configuration of the patch clamp, was also decreased in these cells. Tetrodotoxin (3 mu M), which blocke d whole cell Na+ currents, also blocked veratridine-stimulated Na-22() accumulation. Culturing cells in medium containing 30 mM fructose as an osmotic control had no effect on Na+ flux. Specific [H-3]saxitoxin binding was not affected by 30 mM glucose or 30 mM L-fucose compared with cells grown in unsupplemented medium, suggesting that the number of Na+ channels was not decreased. These studies suggest that exposing cultured neuronal cells to conditions that occur in the diabetic mili eu alters Naf transport and Na+-channel activity.