XANTHINE-OXIDASE ACTIVITY IS NOT INCREASED IN THE COLONIC MUCOSA OF ULCERATIVE-COLITIS

Aim: To measure urate and xanthine by highperformance liquid chromatog raphy in mucosal biopsies from patients with ulcerative colitis and co ntrols, Results: Reactive oxygen metabolite activity was demonstrated by a cystine to cysteine ratio of 0.24 +/- 0.08 in the control biopsie s compared with 1.79 +/- 0.25 in ulcerative colitis, The product to su bstrate ratio (urate to xanthine) for xanthine oxidase and mucosal ura te concentrations were not different between ulcerative colitis patien ts and controls, Xanthine oxidase activity after incubation of homogen ized biopsies was 0.451 (+/- 0.175) nmol.min/mg protein in ulcerative colitis patients compared with 2.585 (+/- 0.823) nmol.min/mg protein i n controls (P < 0.01). Conclusion: These results suggest that xanthine oxidase may not be the major source of superoxide formation in ulcera tive colitis.