Exogenous NG-hydroxyl-L-arginine causes nitrite production in vascular smooth muscle cells in the absence of nitric oxide synthase activity.
Nitric oxide (NO) production from exogenous NG-hydroxy-L-arginine (OH-L-Arg) was investigated in rat aortic smooth muscle cells in culture by measuring nitrite accumulation in the culture medium. As well, the interaction between OH-L-Arg and L-arginine uptake via the y+ cationic amino acid transporter was studied. In cells without NO-synthase activity, OH-L-Arg (1-1000 microM) induced a dose-dependent nitrite production with a half-maximal effective concentration (EC50) of 18.0 +/- 1.5 microM (n = 4-7). This nitrite accumulation was not inhibited by the NO-synthase inhibitor NG-nitro-L-arginine methyl ester, L-NAME (300 microM). In contrast, it was abolished by miconazole (100 microM), an inhibitor of cytochrome P450. Incubation of vascular smooth muscle cells with LPS (10 micrograms/ml) induced an L-NAME inhibited nitrite accumulation, but did not enhance the OH-L-Arg induced nitrite production. OH-L-Arg and other cationic amino acids, L-lysine and L-ornithine, competitively inhibited [3H]-L-arginine uptake in rat aortic smooth muscle cells, with inhibition constants of 195 +/- 23 microM (n = 12), 260 +/- 40 microM (n = 5) and 330 +/- 10 microM (n = 5), respectively. These results show that OH-L-Arg is recognized by the cationic L-amino acid carrier present in vascular smooth muscle cells can be oxidized to NO and nitrite in these cells in the absence of NO-synthase, probably by cytochrome P450 or by a reaction involving a cytochrome P450 by-product.
Schott
C A
CA
Université Louis Pasteur de Strasbourg, Laboratoire de Pharmacologie Cellulaire et Moléculaire, CNRS URA600, Illkirch, France.
Bogen
C M
CM
Vetrovsky
P
P
Berton
C C
CC
Stoclet
J C
JC
D000594:Amino Acid Oxidoreductases / Q000096:biosynthesis / Q000378:metabolism*; D000818:Animals; D001120:Arginine / Q000031:analogs & derivatives* / Q000378:metabolism / Q000494:pharmacology; D002352:Carrier Proteins / Q000378:metabolism; D002478:Cells, Cultured; D004790:Enzyme Induction; D008297:Male; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000187:drug effects* / Q000201:enzymology / Q000378:metabolism; D019001:Nitric Oxide Synthase; D009573:Nitrites / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar
D002352:Carrier Proteins; D009573:Nitrites; C068309:N(omega)-hydroxyarginine; D001120:Arginine; D019001:Nitric Oxide Synthase; D000594:Amino Acid Oxidoreductases