REDUCED NA+ K+ ATPASE TRANSPORT ACTIVITY, RESTING MEMBRANE-POTENTIAL,AND BRADYKININ-STIMULATED PHOSPHATIDYLINOSITOL SYNTHESIS BY POLYOL ACCUMULATION IN CULTURED NEUROBLASTOMA-CELLS/

In these studies we examined the effect of polyol accumulation on neur al cell myo-inositol metabolism and properties. Neuroblastoma cells we re cultured for two weeks in media containing 30 mM glucose, fructose, galactose or mannose with or without 0.4 mM sorbinil or 250 mu M myo- inositol. Chronic exposure of neuroblastoma cells to media containing 30 mM glucose, galactose, or mannose caused a decrease in myo- inosito l content and myo-[2-H-3]inositol accumulation and incorporation into phosphoinositides compared to cells cultured in unsupplemented medium or medium containing 30 mM fructose as an osmotic control. These monos accharides each caused an increase in intracellular polyol levels with galactitol > sorbitol = mannitol accumulation. Chronic exposure of ne uroblastoma cells to media containing 30 mM glucose, galactose, or man nose caused a significant decrease in Na+/K+ ATPase transport activity , resting membrane potential, and bradykinin-stimulated P-32 incorpora tion into phosphatidylinositol compared to cells cultured in medium co ntaining 30 mM fructose. In contrast, basal incorporation of P-32 into phosphatidylinositol or basal and bradykinin-stimulated P-32 incorpor ation into phosphatidylinositol 4,5-bisphosphate were not effected. Ea ch of these cellular functions as well as myo-inositol metabolism and content and polyol levels remained near control values when 0.4 mM sor binil, an aldose reductase inhibitor, was added to the glucose, galact ose, or mannose supplemented media. myo-Inositol metabolism and conten t and bradykinin-stimulated phosphatidylinositol synthesis were also m aintained when media containing 30 mM glucose, galactose, or mannose w as supplemented with 250 mu M myo-inositol. The results suggest that p olyol accumulation induces defects in neural cell myo-inositol metabol ism and certain cell functions which could, if they occurred in vivo, contribute to the pathological defects observed in diabetic neuropathy .