INHIBITION OF SODIUM-PHOSPHATE COTRANSPORT IN RENAL BRUSH-BORDER MEMBRANES WITH THE STILBENEDISULFONATE, H-2-DIDS

Membrane proteins involved with sodium/phosphate cotransport across the renal brush border provide the sensitive control for phosphate homeostasis. The present study describes the inhibition of sodium/phosphate cotransport with the stilbenedisulfonate derivatives, DIDS and H-2-DIDS. Preincubation of the rat brush-border membrane vesicles with H-2-DIDS led to the inhibition of sodium-dependent phosphate uptake with a half maximal concentration, IC50, of about 10-mu-M. The inhibition was irreversible supporting the notion that H-2-DIDS forms covalent bonds with the cotransporter. The cotransporter could be protected by excess sodium phosphate but not sodium chloride, sodium sulfate, sodium succinate, sodium bicarbonate, nor sodium phosphonoformate. These observations suggest that the stilbenedisulfonates may be useful in labeling the sodium/phosphate cotransporter within renal brush-border membranes.