Nitric oxide generation from hydroxylamine in the presence of neutrophils and in the cell-free system

Conversion of hydroxylamine (HA) to nitric oxide (NO) has been studied in t he presence or absence of human neutrophils with or without myristate aceta te phorbol (PMA), catalase (CAT), hydrogen peroxide (H2O2), and superoxide dismutase (SOD) and nitric oxide synthase (NOS) inhibitors. The generation of NO from HA in the presence of neutrophils was higher than in the cell-fr ee system. We found that catalase did not influence the nitrite generation from HA in the cell-free system and in the presence of neutrophils. The H2O 2 enhanced the NO generation from HA in the presence of neutrophils only. W hen catalase and H2O2 were added together, a high increase of NO generation from HA in both systems was observed. The addition of SOD decreased wherea s addition of PMA enhanced the NO generation from HA in the presence of neu trophils. The presented data show the possible role of oxygen radicals in t he decomposition of HA to NO. The addition of NOS inhibitors to the culture of neutrophils decreased the generation of nitrite from HA. Our results su ggest that NO generation from HA, which is an intermediate in NO production from L-arginine, may be supported by an enzymatic pathway in which cellula r NO synthase is involved.