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 μmol/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±0.42mg/g of hemoglobin, 6.2±0.13 μmol/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 μmol/l in the healthy controls and 56.3±3.9 μmol/l in cancer patients. Conclusion: Urinary hydrogen peroxide may be a marker of oxidative stress in malignancies.