Characterization of L-arginine transport by pulmonary artery endothelial cells
Greene, B.; Pacitti, A.J.; Souba, W.W.
American Journal of Physiology 264(4 Pt 1): L351-L356
1993
ISSN/ISBN: 0002-9513 PMID: 8476065 Document Number: 419956
The transport of L-arginine by porcine pulmonary artery endothelial cells (PAECs) was characterized. Uptake of 50 mu-M L-arginine was time dependent and linear in the presence and absence of sodium, with apprx 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 (K-m) = 304 +- 23 mu-M, maximal transport velocity (V-max) = 679 +- 34 pmol cntdot mg protein-1 cntdot 30 s-1), and a low-affinity carrier (K-m = 3.9 +- 1.0 mM, V-max = 2.8 +- 0.7 nmol/mg protein-1 cntdot 30 s-1). Saturable Na+-independent uptake of 50 mu-M 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 (K-m = 62 +- 3 mu-M, V-max = 211 +- 24 pmol cntdot mg protein-1 cntdot 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 B-O,+.