Nitric oxide synthesis is increased in patients with systemic lupus erythematosus.

Nitric oxide (NO) is believed to have a role in the inflammatory process. NO production was measured in 26 patients with systemic lupus erythematosus (SLE) and 20 healthy volunteers, using spectrophotometrically determined serum nitrite and citrulline as surrogate markers. Both nitrite and citrulline levels were significantly higher in patients with SLE than in controls (P < 0.001). Twelve and 10 patients, respectively, with SLE had nitrite and citrulline levels that were two standard deviations higher than the mean level of controls. These patients had a significantly higher measure of disease activity (SLE Disease Activity Index). These data show that there is increased NO production in SLE and that it may serve as a marker for disease activity.