Facilitated transport of L-phenylalanine across blood-nerve barrier of rat peripheral nerve.
L-Phenylalanine transport across the blood-nerve barrier was studied by perfusing Ringer solution containing trace amounts of L-[14C]phenylalanine and [3H]dextran (a vascular marker) through the hindlimb of an anesthetized rat. At the end of perfusion, a segment of sciatic nerve was removed, frozen, desheathed, and processed for radioactivity counting. The permeability-surface area product of the blood-nerve barrier (PABNB) to L-[14C]phenylalanine decreased from 58 +/- 9 X 10(-5) to 1.7 +/- 0.3 X 10(-5) (SE) ml.s-1.g wet wt-1, as the perfusate concentration of unlabeled L-phenylalanine was increased to 10 mM. D-Phenylalanine had less of an inhibitory effect on L-[14C]phenylalanine uptake than did L-phenylalanine. PABNB did not change in the presence of 50 mM alpha-(methylamino)isobutyric acid (MeAIB) in the perfusion medium, nor by replacing NaCl by Tris.HCl. However, addition of 50 mM 2-aminobicyclo(2,2,1)heptane-2-carboxylic acid (BCH) reduced PABNB to 2.1 +/- 0.3 X 10(-5) ml.s-1.g wet wt-1 (n = 4). PA at epiperineurial barrier (PAper) of L-[14C]phenylalanine at the epiperineurial barrier, determined from in situ incubation, was 1.4 +/- 0.2 X 10(-5) ml.s-1.g wet wt-1 (n = 6) and was unaffected by 10 mM L-phenylalanine concentration in the incubation medium. The results demonstrate for the first time carrier-mediated transport system for L-phenylalanine at the blood-nerve barrier of the rat peripheral nerve.
Wadhwani
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KC
Laboratory of Neurosciences, National Institute on Aging, National Institutes of Health, Bethesda, Maryland 20892.
Smith
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Rapoport
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SI
D000596:Amino Acids / Q000494:pharmacology; D000598:Amino Acids, Cyclic; D000621:Aminoisobutyric Acids / Q000494:pharmacology; D000818:Animals; D001692:Biological Transport; D002199:Capillary Permeability; D007275:Injections, Intravenous; D008297:Male; D009994:Osmolar Concentration; D010477:Perfusion / Q000379:methods; D010525:Peripheral Nerves / Q000098:blood supply / Q000378:metabolism*; D010649:Phenylalanine / Q000097:blood / Q000493:pharmacokinetics*; D051381:Rats; D013395:Sucrose / Q000493:pharmacokinetics; D013997:Time Factors
D000596:Amino Acids; D000598:Amino Acids, Cyclic; D000621:Aminoisobutyric Acids; C006504:2-aminobicyclo(2,2,1)heptane-2-carboxylic acid; C017911:2-(methylamino)isobutyric acid; D010649:Phenylalanine; D013395:Sucrose