Effect of <I>t</I>-butylhydroperoxide on Na<SUP>+</SUP>-dependent Glutamate Uptake in Rabbit Brain Synaptosome

Effect of <I>t</I>-butylhydroperoxide on Na<SUP>+</SUP>-dependent Glutamate Uptake in Rabbit Brain Synaptosome

<P> The effect of an organic peroxide, <I>t</I>-butylhydroperoxide (<I>t</I>-BHP), on glutamate uptake was studied in synaptosomes prepared from cerebral cortex. <I>t</I>-BHP inhibited the Na<SUP>+</SUP>-dependent glutamate uptake with no change in the Na<SUP>+</SUP>-independent uptake. This effect of <I>t</I>-BHP was not altered by addition of Ca<SUP>2+</SUP> channel blockers (verapamil, diltiazem and nifedipine) or PLA<SUB>2</SUB> inhibitors (dibucaine, butacaine and quinacrine). However, the effect was prevented by iron chelators (deferoxamine and phenanthroline) and phenolic antioxidants (<I>N,N </I>-diphenyl-phenylenediamine, butylated hydroxyanisole, and butylated hydroxytoluene). At low concentrations (＜1.0 mM), <I>t</I>-BHP inhibited glutamate uptake without altering lipid peroxidation. Moreover, a large increase in lipid peroxidation by ascorbate/Fe<SUP>2+</SUP> was not accompanied by an inhibition of glutamate uptake. The impairment of glutamate uptake by <I>t</I>-BHP was not intimately related to the change in Na<SUP>+</SUP>-K<SUP>+</SUP>-ATPase activity. These results suggest that inhibition of glutamate uptake by <I>t</I>-BHP is not totally mediated by peroxidation of membrane lipid, but is associated with direct interactions of glutamate transport proteins with <I>t</I>-BHP metabolites. The Ca<SUP>2+</SUP> influx through Ca<SUP>2+</SUP> channel or PLA<SUB>2</SUB> activation may not be involved in the <I>t</I>-BHP inhibition of glutamate transport.