EXPRESSION OF NITRIC-OXIDE SYNTHASE IN ULCERATIVE-COLITIS

Nitric oxide (NO) is generated from L-arginine by a family of enzymes called the NO synthases. Previous investigators have proposed that the expression of this inducible enzyme (iNOS) may account for the charac teristic vasodilatation, oedema and impairment of gut motility seen in active ulcerative colitis. Using a specific antibody to iNOS, we have investigated the distribution of this enzyme in colonic tissue from p atients with histologically proven ulcerative colitis. Eight patients with ulcerative colitis expressed calcium-independent citrulline activ ity (9.96 +/- 2.34 pmol citrulline mg(-1) protein min(-1)) and showed immunoreactivity to the iNOS antibody within the inflammatory infiltra te of the lamina propria, and also within the cytoplasm of the epithel ial cells lining the colon. Five age-matched controls showed no calciu m-independent citrulline activity (0.2 +/- 0.08 pmol citrulline mg(-1) protein min(-1)) and no immunoreaction to the antibody. We conclude t hat this enzyme is present in colonic tissue including the epithelium from patients with active colitis. Inhibition of this enzyme may provi de a novel therapeutic option for patients with active ulcerative coli tis.