NITRIC-OXIDE PRODUCTION BY ACTIVATED HUMAN NEUTROPHILS EXPOSED TO SODIUM-AZIDE AND HYDROXYLAMINE - THE ROLE OF OXYGEN RADICALS

The occurrence of a nitric oxide-generating system in human neutrophil s has been controversial and the detection of nitric oxide rendered mo re difficult due to the capacity of oxygen radicals and other compound s to scavenge this molecule. Our results demonstrate that human neutro phils, when stimulated by adherence or by phorbol myristate acetate ge nerate nitrite upon exposure to NaN3 or hydroxylamine. NaN3-dependent nitrite production was further increased by the addition of superoxide dismutase (SOD). The generation of nitrite was also stimulated by exo genous added H2O2 in resting neutrophils and could be induced in a cel l-free system containing heme-enzymes, H2O2 and NaN3, suggesting a req uirement for H2O2-mediated oxidation of NaN3 in nitrite formation by t he stimulated cells, Treatment of the neutrophils with hydroxylamine l ed to the production of even larger quantities of nitrite (>25 nmol/h. 10(6) cells), an effect that was prevented by SOD, pointing to supero xide as a metabolite possibly involved in nitrite formation. These res ults emphasize the importance of oxygen radicals or other intermediate s in the generation of nitrite by stimulated neutrophils exposed to th e above compounds. (C) 1994 Academic Press, Inc.