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.
