Elevated serum nitrate concentrations in active spondyloarthropathies.

We determined the concentrations of nitrate, reflecting endogenous nitric oxide (NO) production, by gas chromatography in the sera of patients with spondyloarthropathy. In those patients with active disease, as indicated by elevated C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR) serum nitrate levels (n = 7; mean 73.2 +/- s.d. 21.7 mumol/l) were significantly (P < 0.001) increased in comparison to patients with inactive spondyloarthropathy (n = 7; 31.7 +/- 9.5 mumol/l) and healthy volunteers (n = 10; 33.4 +/- 15.9 mumol/l). The nitrate serum levels correlated closely with CRP and ESR (r = 0.8, P < 0.001, each). There were no major differences in dietary nitrate intake between the study groups. The increased concentrations of serum nitrate in patients with active spondyloarthropathy indicate that NO production is enhanced in these patients.