MICROMOLAR CONCENTRATIONS OF BROMOSULFOPHTHALEIN AFFECT TRANSPORT OF D-GLUCOSE, L-ALANINE AND P-AMINOHIPPURATE IN RAT RENAL BRUSH-BORDER MEMBRANES

The effect of bromosulfophthalein (BSP) on potential-stimulated p-amin ohippurate (PAH) uptake as well as on Na+-D-glucose and Na+-L-alanine cotransport was investigated in rat renal brush-border membrane vesicl es. All three transport mechanisms were inhibited by BSP in the follow ing order: PAH>D-glucose>L-alanine. Half-maximal inhibition of initial uptakes was observed at approximately 10, 75 and 250 mu M BSP, respec tively. The inhibition of initial Na+-D-glucose uptake could not be at tributed to increased cation permeability, since equilibrium exchange was equally affected by BSP. The nonspecific short-term inhibition of unrelated transport systems by BSP suggests a more general effect, suc h as a change in membrane fluidity. In addition, long-term incubation with 0.5 mM BSP resulted in a loss of vesicle integrity.