Exogenous N G-hydroxy- l-arginine causes nitrite production in vascular smooth muscle cells in the absence of nitric oxide synthase activity

• Published in: FEBS letters 1994-03, Vol.341 (2), p.203-207
• Main Authors: Schott, C.A., Bogen, C.M., Vetrovsky, P., Berton, C.C., Stoclet, J.C.
• Format: Article
• Language: English
• Subjects: Arginine uptake; NG-Hydroxy- l-arginine; Nitric oxide; NO-synthase; Smooth muscle cell
• ISSN: 0014-5793; 1873-3468
• DOI: 10.1016/0014-5793(94)80457-5

Nitric oxide (NO) production from exogenous N G-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 μM) induced a dose-dependent nitrite production with a half-maximal effective concentration (EC 50) of 18.0 ± 1.5 μM ( n = 4–7). This nitrite accumulation was not inhibited by the NO-synthase inhibitor N G-nitro- l-arginine methyl ester, l-NAME (300 μM). In contrast, it was abolished by miconazole (100 μM), an inhibitor of cytochrome P 450. Incubation of vascular smooth muscle cells with LPS (10 μg 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 m rat aortic smooth muscle cells, with inhibition constants of 195 ± 23 μM( n = 12), 260 ± 40 μM( n= 5) and 330 ± 10 μM( 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 and can be oxidized to NO and nitrite in these cells in the absence of NO-synthase, probably by cytochrome P 450 or by a reaction involving a cytochrome P 450 byproduct.