RECTAL SUBSTANCE-P CONCENTRATIONS ARE INCREASED IN ULCERATIVE-COLITISBUT NOT IN CROHNS-DISEASE

Substance P, a neurotransmitter found in colonic mucosa, can alter gut immunologic, vascular, and motor phenomena. Thus, it may have an impo rtant role in the pathogenesis of ulcerative colitis (UC) and Crohn's disease (CD). By radioimmunoassay of the extracts of endoscopically ob tained rectal mucosal biopsies in affected patients, we evaluated muco sal substance P levels. Non-inflammatory bowel disease patients underg oing lower endoscopies and biopsies served as controls. There were sig nificantly increased concentrations of substance P in patients with UC , compared with controls (p < 0.05) and compared with patients with CD (p < 0.005). The mucosal levels in CD patients were significantly low er than in controls (p < 0.05). Patients with active rectal CD had low er levels than patients with no evidence of active rectal disease. For the CD and UC patients, there was a strongly positive correlation bet ween rectal mucosal substance P concentrations and total histologic in flammation scores (r = 0.7, p = 0.001). A strong correlation existed f or rectal mucosal substance P concentrations and mucosal mononuclear c ell scores (r = 0.7, p = 0.001) and for rectal mucosal substance P con centrations and the combined scores of mucosal neutrophils and eosinop hils (r = 0.7, p = 0.002). In conclusion, the rectal mucosal substance P concentrations in patients with UC and CD are significantly differe nt. Thus, substance P may have a different role in the pathogenesis of each of these entities. It is possible that the elevated concentratio ns in patients with UC are contributing to the increased inflammation seen in these patients. Alternatively, measured mucosal substance P le vels may simply reflect the end result of the different inflammatory p rocesses in UC and CD, rather than the cause. It is possible that the inflammatory cells are contributing to the measured concentrations.