Inhibition of human renal epithelial Na+/Pi cotransport by phosphonoformic acid

Phosphonoformic acid was a potent competitive inhibitor of Na+/Pi cotransport by brush border membrane vesicles isolated from human renal cortex (Ki 31 microM). The Na+/Pi cotransport system in rat renal brush border membrane vesicles was much less sensitive to inhibition (Ki 210 microM). Na+/Pi cotransport by cultured cells derived from human renal cortex also was inhibited by phosphonoformic acid. Both in isolated membranes and cells the inhibition was dose-dependent, competitive, and specific for Pi. The effectiveness of phosphonoformic acid on Na+/Pi cotransport in human kidney suggests that its administration may be a useful maneuver to increase renal Pi excretion.