Interaction of nitrogen dioxide with human plasma Antioxidant depletion and oxidative damage

Nitrogen dioxide (NO* 2 ) is often present in inhaled air and may be generated in vivo from nitric oxide. Exposure of human blood plasma to NO* 2 caused rapid losses of ascorbic acid, uric acid and protein thiol groups, as well as lipid peroxidation and depletions of α‐tocopherol, bilirubin and ubiquinol‐10. No increase in protein carbonyls was detected. Supplementation of plasma with ascorbate decreased the rates of lipid peroxidation. α‐tocopherol depletion and loss of uric acid. Uric acid supplementation decreased rates of lipid peroxidation but not the loss of α‐tecopherol. We conclude that ascorbic acid, protein ‐SH groups, uric acid and α‐tocopherol may be important agents protecting against NO* 2 in vivo. If these antioxidants are depleted, peroxidation of lipids occurs and might contribute to the toxicity of NO* 2 .