Direct determination of colonic nitric oxide level - A sensitive marker of disease activity in ulcerative colitis

Objective: In active ulcerative colitis, colonic nitric oxide (NO) generation is enhanced and probably has an important role in its pathogenesis. We tested the reliability of an NO electrode in monitoring colonic NO levels in ulcerative colitis patients and control subjects and its possible usage as a marker of disease activity. Methods: Colonic NO level was determined by the NO detection system model NO-501 (InterMedical, Nagoya, Japan). The working electrode was inserted into a 7-mm diameter polyvinyl tube and introduced at a distance 6 cm from the anus. In each subject sigmoidoscopy was performed and mucosal biopsies were obtained. NO synthase (NOS) activity was determined by monitoring the conversion of ³H-arginine to citrulline. Results: Colonic NO level is significantly increased in patients with active ulcerative or Crohn's colitis-more than 2-fold higher than in control subjects. There was good correlation between colonic NO level and NOS activity and the clinical and endoscopic indices of disease activity. Conclusion: Direct determination of colonic NO level is convenient, and reliable, and may help to monitor disease activity in ulcerative colitis.