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Xanthine oxidase activity is not increased in the colonic mucosa of ulcerative colitis
P D Reynolds1, S T Rhenius, J O Hunter
1Department of Gastroenterology, Addenbrooke's Hospital, Cambridge, UK.
Aim:
To measure urate and xanthine by high-performance liquid chromatography in mucosal biopsies from patients with ulcerative colitis and controls.
Results:
Reactive oxygen metabolite activity was demonstrated by a cystine to cysteine ratio of 0.24 +/- 0.08 in the control biopsies compared with 1.79 +/- 0.25 in ulcerative colitis. The product to substrate ratio (urate to xanthine) for xanthine oxidase and mucosal urate concentrations were not different between ulcerative colitis patients and controls. Xanthine oxidase activity after incubation of homogenized biopsies was 0.451 (+/- 0.175) nmol.min/mg protein in ulcerative colitis patients compared with 2.585 (+/- 0.823) nmol.min/mg protein in controls (P < 0.01).
Conclusion:
These results suggest that xanthine oxidase may not be the major source of superoxide formation in ulcerative colitis.