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-aminohippurate (PAH) uptake as well as on Na+-D-glucose and Na+-L-alanine cotransport was investigated in rat renal brush-border membrane vesicles. All three transport mechanisms were inhibited by BSP in the following order: PAH>D-glucose>L-alanine. Half-maximal inhibition of initial uptakes was observed at approximately 10, 75 and 250 mu M BSP, respectively. The inhibition of initial Na+-D-glucose uptake could not be attributed 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, such as a change in membrane fluidity. In addition, long-term incubation with 0.5 mM BSP resulted in a loss of vesicle integrity.