Abstract
OBJECTIVES—To determine the feasibility of monitoring the serum concentration of NG-hydroxy-L-arginine (L-NHA) as an index of an increased nitric oxide (NO) synthase activity in patients with rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE) compared with nitrate (NO3 ), the major circulating metabolite of NO whose concentration is influenced by dietary intake. METHODS—The serum concentrations of L-NHA, L-arginine (L-Arg), and NO3 were determined in 33 patients with RA, 25 patients with SLE and, 29 healthy subjects. RESULTS—Serum L-NHA was significantly increased in RA patients with high disease activity (287% of control, p<0.01), but not with low disease activity (115%), as well as in patients with SLE (173%, p<0.01). In contrast, serum NO3 did not differ significantly between either group of patients and the respective control group. CONCLUSION—NO synthase activity or expression, or both, is upregulated in RA patients with high disease activity and in patients with SLE. Serum L-NHA seems to be a more specific and reliable index of an increased activity of this enzyme in patients with acute or chronic inflammatory diseases than NO3 .
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Figure 1 .
Serum concentration of NG-hydroxy-L-arginine (L-NHA) in the groups of patients with RA of high inflammatory activity (RA+, n=12) and low inflammatory activity (RA-, n=21), in the group of patients with systemic lupus erythematosus (SLE, n=25), and in the respective control groups (Con). The figure depicts the individual concentrations of each patient or control subject, as determined by HPLC analysis, and the means (SD). Only in the RA+ group did the L-NHA concentrations not follow a Gaussian distribution, so that the non-parametric Mann-Whitney U test instead of the Student's t test was used for statistical analysis.