Urinary hydrogen peroxide: a probable marker of oxidative stress in malignancy

BACKGROUND: Urinary hydrogen peroxide was postulated to be a biomarker of oxidative stress. We estimated urinary hydrogen peroxide along with other established parameters of oxidative stress in malignancies where oxidative stress is well documented. METHODS: The oxidative stress markers tested were concentrations of erythrocyte glutathione, erythrocyte malonaldehyde (MDA) and plasma hydroperoxide, and activities of plasma glutathione-S-transferase (GST) and erythrocyte catalase. Urinary hydrogen peroxide was measured by a modified ferrous ion oxidation xylenol orange version-2 (FOX-2) method on a spot random sample of urine. RESULTS: In healthy controls (n=10), erythrocyte glutathione concentration was 4.41+/-0.057mg/g of hemoglobin, plasma hydroperoxide was 2.5+/-0.07 micromol/l, erythrocyte MDA was 0.9+/-0.15 nmol/ml of packed cell suspension and erythrocyte catalase and plasma GST were 74.66+/-9.2/s/ml of packed cell suspension and 6.12+/-0.84 IU/l, respectively. In cancer patients (n=25), erythrocyte glutathione, plasma hydroperoxide and erythrocyte MDA were 9.32+/-0.42 mg/g of hemoglobin, 6.2+/-0.13 micromol/l and 2.3+/-0.27 nmol/ml of packed cell suspension, respectively; and activities of erythrocyte catalase and plasma GST were 151.04+/-6.5/s/ml of packed cell suspension and 10.9+/-0.36 IU/l, respectively. Urinary hydrogen peroxide concentration was 15+/-9.8 micromol/l in the healthy controls and 56.3+/-3.9 micromol/l in cancer patients. CONCLUSION: Urinary hydrogen peroxide may be a marker of oxidative stress in malignancies.