Since the generation of superoxide and hydrogen peroxide by NADPH oxidase and nitric oxide (NO) by NO synthase (NOS) in granulocytes is NADPH-dependent, we investigated the production of NO, superoxide and H P O P in glucose 6-phosphate dehydrogenase (G6PD)-deficient human granulocytes. Our results showed that upon stimulation with either 5 W Wg/ml of lipopolysaccharide (LPS) or 10 W WM of phorbol 12-myristate 13-acetate (PMA), the production of nitrite in normal granulocytes was elevated, 252 þ 135% and 239 þ 72%, respectively, compared to the resting stage. In contrast, G6PD-deficient granulocytes did not produce more nitrite upon stimulation with either LPS or PMA compared to the resting stage. Western blot analysis indicated a normal expression pattern of inducible NOS in G6PD-deficient granulocytes. In addition, the production of H P O P and superoxide was also significantly impaired in G6PD-deficient granulocytes compared to control cells. These data demonstrate that G6PD deficiency causes an impairment in the production of NO, superoxide and H P O P .z 1998 Federation of European Biochemical Societies.