Na+-independent l-arginine transport in rabbit renal brush border membrane vesicles |
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Authors: | Marc R Hammerman |
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Institution: | 1. Renal and Metabolism Divisions, Department of Internal Medicine, Washington University School of Medicine, St. Louis, MO 63110 U.S.A.;2. Laboratory of Molecular Aging, Gerontology Research Center, National Institute on Aging, National Institutes of Health, Baltimore City Hospital, Baltimore, MD 21224 U.S.A. |
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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. |
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Keywords: | Brush border vesicle Amino acid transport L-Arginine (Rabbit kidney) FCCP Hepes Mes Address for correspondence: Department of Internal Medicine Washington University School of Medicine 660 South Euclid Avenue St Louis MO 63110 U S A |
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