Role of Phospholipase A<SUB>2</SUB> in Oxidant-induced Alteration in Phosphate Transport in Primary Cultured Rabbit Renal Proximal Tubule Cells

Role of Phospholipase A<SUB>2</SUB> in Oxidant-induced Alteration in Phosphate Transport in Primary Cultured Rabbit Renal Proximal Tubule Cells

<P> The present study was undertaken to examine the role of phospholipase A<SUB>2</SUB> (PLA<SUB>2</SUB>) in oxidant-induced inhibition of phosphate transport in primary cultured rabbit renal proximal tubule cells. Uptakes of phosphate and glucose were dose-dependently inhibited by an oxidant <I>t</I>-butylhydroperoxide (<I>t</I>BHP), and the significant inhibition appeared at 0.025 mM of <I>t</I>BHP, whereas <I>t</I>BHP-induced alterations in lipid peroxidation and cell viability were seen at 0.5 mM. <I>t</I>BHP stimulated arachidonic acid (AA) release in a dose- dependent fashion. A PLA<SUB>2</SUB> inhibitor mepacrine prevented <I>t</I>BHP-induced AA release, but it did not alter the inhibition of phosphate uptake and the decrease in cell viability induced by <I>t</I>BHP. <I>t</I>BHP-induced inhibition of phosphate transport was not affected by a PKC inhibitor, staurosporine. <I>t</I>BHP at 0.1 mM did not produce the inhibition of Na<SUP>&#8290;</SUP>-K<SUP>&#8290;</SUP>-ATPase activity in microsomal fraction, although it significantly inhibited at 1.0 mM. These results suggest that <I>t</I>BHP can inhibit phosphate uptake through a mechanism independent of PLA<SUB>2 </SUB>activation, irreversible cell injury, and lipid peroxidation in primary cultured rabbit renal proximal tubular cells.