Micromolar Concentrations of Bromosulfophthalein Affect Transport of <i>D</i>-Glucose, <i>L</i>-Alanine and <i>p</i>-Aminohippurate in Rat Renal Brush-Border Membranes

Abstract

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 µM 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.