Inflammatory nitrite at low pH in active colitis: A promotor of malignancy?

Abstract

Problem: Cancer development in chronic ulcerative colitis is epidemiologically related to the number and severity of acute attacks of colitis. Quantifying luminal nitrite during active and quiescent colitis should reflect immune cell production of nitric oxide which, depending on time or extent of exposure, may promote tumorigenesis. Cases and methods: Cases were either a healthy control group (21), acute ulcerative colitis (16) or quiescent ulcerative colitis (12). Proctoscopic placement of dialysis tubing in the rectum was made for 60 minutes. The volume in each tube was 1.5 mL which contained a non-dialysable volume marker of labelled dextran. The pH, pCO2 was measured by micro gas analysis and nitrite measured spectrophotometrically using the Griess reaction. Calculations on volume corrected dialysate were made. Results: Control and quiescent colitis cases had no measurable nitrite. The mean ± SE of nitrite in 16 cases of acute UC was 9.7 ± 2.6 mmol/mL but only 77% of dialysate showed detectable nitrites. The pH in healthy controls was 7.64 ± .03 (21), acute colitis 7.14 ± .05 (p < .01) and quiescent colitis 7.55 (10). Conclusion: Nitrite formation by the inflamed colonic mucosa in UC is very significant and found at a lower pH than in control cases. The extent and duration of nitrite exposure of colonic epithelial cells in acute colitis may be an important factor leading to nucleic acid changes induced by NO.