Characterization of L-arginine transport by pulmonary artery endothelial cells.
The transport of L-arginine by porcine pulmonary artery endothelial cells (PAECs) was characterized. Uptake of 50 microM L-arginine was time dependent and linear in the presence and absence of sodium, with approximately 70% of uptake occurring via a carrier-mediated Na(+)-independent process. Kinetic studies of saturable Na(+)-independent transport revealed two transport components: a high-affinity transporter [Michaelis constant (Km) = 304 +/- 23 microM, maximal transport velocity (Vmax) = 679 +/- 34 pmol.mg protein-1.30 s-1], and a low-affinity carrier (Km = 3.9 +/- 1.0 mM, Vmax = 2.8 +/- 0.7 nmol/mg protein-1.30 s-1). Saturable Na(+)-independent uptake of 50 microM L-arginine transport showed no significant variation in uptake between pH 6.0 and 8.0 and was blocked by the system y+ substrates L-arginine, L-homoarginine, L-lysine, and L-ornithine. Na(+)-dependent L-arginine transport occurred via a single high-affinity system (Km = 62 +/- 3 microM, Vmax = 211 +/- 24 pmol.mg protein-1.30 s-1) which was significantly inhibited by L-arginine, L-lysine, L-ornithine, L-leucine, L-alanine, L-cysteine, and L-glutamine, but not by 2-methylaminoisobutyric acid. Na(+)-dependent arginine uptake was pH and hormone insensitive, and lithium did not substitute effectively for sodium. These data are consistent with mediation of high-affinity arginine transport by PAECs via Na(+)-independent system y+ and Na(+)-dependent system BO,+.
Greene
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B
Department of Surgery, University of Florida College of Medicine, Gainesville.
Pacitti
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AJ
Souba
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D000596:Amino Acids / Q000494:pharmacology; D000818:Animals; D001120:Arginine / Q000378:metabolism*; D001692:Biological Transport / Q000187:drug effects; D002478:Cells, Cultured; D002794:Choline / Q000494:pharmacology; D004730:Endothelium, Vascular / Q000378:metabolism*; D007700:Kinetics; D011651:Pulmonary Artery / Q000502:physiology*; D012964:Sodium / Q000378:metabolism / Q000494:pharmacology; D013552:Swine; D014316:Tritium
D000596:Amino Acids; D014316:Tritium; D001120:Arginine; D012964:Sodium; D002794:Choline