Distribution of inducible nitric oxide synthase in ulcerative colitis.

To investigate reports that the biosynthesis of nitric oxide (NO) is increased in the colonic mucosa of patients with active ulcerative colitis (UC), which suggests that serum NOx levels may be an important indicator of UC activity. To determine the role of NO within the colon, we purchased polyclonal antibodies against human-inducible NO synthase (iNOS). We then examined the distribution of iNOS-reactive cells in UC colon tissues. In specimens from 12 UC patients, iNOS-positive neutrophils and macrophages were observed at the base of the ulcer but not in distant areas in the active stage. iNOS expression in colon mucosa was virtually absent during the inactive stage of UC and within the colon of patients with non-UC colitis. We conclude that NO in colonic mucosa may play a potential role in the pathogenesis of UC.