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.