Na +-independent l-arginine transport in rabbit renal brush border membrane vesicles

Abstract

Na +-independent l-arginine uptake was studied in rabbit renal brush border membrane vesicles. The finding that steady-state uptake of l-arginine decreased with increasing extravesicular osmolality and the demonstration of accelerative exchange diffusion after preincubation of vesicles with l-arginine, but not d-arginine, indicated that the uptake of l-arginine in brush border vesicles was reflective of carrier-mediated transport into an intravesicular space. Accelerative exchange diffusion of l-arginine was demonstrated in vesicles preincubated with l-lysine and l-ornithine, but not l-alanine or l-proline, suggesting the presence of a dibasic amino acid transporter in the renal brush border membrane. Partial saturation of initial rates of l-arginine transport was found with extravesicular [arginine] varied from 0.005 to 1.0 mM. l-Arginine uptake was inhibited by extravesicular dibasic amino acids unlike the Na +-independent uptake of l-alanine, l-glutamate, glycine or l-proline in the presence of extravesicular amino acids of similar structure. l-Arginine uptake was increased by the imposition of an H + gradient (intravesicular pH<extravesicular pH) and H + gradient stimulated uptake was further increased by FCCP. These findings demonstrate membrane-potential-sensitive, Na +-independent transport of l-arginine in brush border membrane vesicles which differs from Na +-independent uptake of neutral and acidic amino acids. Na +-independent dibasic amino acid transport in membrane vesicles is likely reflective of Na +-independent transport of dibasic amino acids across the renal brush border membrane.