Reduction of 1-nitroso-2-naphthol by NADPH in the presence of liver microsomes.

1. The endogenous, NADPH-supported production of H2O2 and of O2-.-radicals in liver microsomes, was very strongly enhanced in the presence of 1-nitroso-2-naphthol. 2. A 30-fold induction by NON was the consequence of its direct reduction to NON-radicals, catalyzed by microsomal NADPH:cytochrome P450 reductase. 3. Nitroso radicals reduce molecular oxygen to superoxide anion radicals, which were readily dismutated by superoxide dismutase to hydrogen peroxide. 4. O2-.-radicals were the sole precursors of all NON-induced production of H2O2 in liver microsomes.