Hydrogen peroxide in human urine: Implications for antioxidant defense and redox regulation

The presence of hydrogen peroxide, at levels sometimes exceeding 100 mu M, in human urine samples was established by three different assay methods: 2-oxoglutarate decarboxylation and the ferrous oxidation-xylenol orange (FOX) assay and an oxygen electrode. Detected levels of H2O2 were decreased by addition of superoxide dismutase. We conclude that urine contains autooxidizable molecules that, upon exposure to 21% O-2, undergo rapid superoxide-dependent autooxidation reactions to generate H2O2. The exposure of human tissues to hydrogen peroxide may be greater than is commonly supposed, which has implications in relation to the proposed role of this species in cell signaling. (C) 1999 Academic Press.