KINETICS OF NITRIC-OXIDE AND HYDROGEN-PEROXIDE PRODUCTION AND FORMATION OF PEROXYNITRITE DURING THE RESPIRATORY BURST OF HUMAN NEUTROPHILS

Nitric oxide ((NO)-N-.) release, oxygen uptake and hydrogen peroxide ( H2O2) production elicited by increasing phorbol 12-myristate 13-acetat e (PMA) concentrations were measured in human neutrophils. Half-maxima l activities were sequentially elicited at about 0.0001-0.001 mu g PMA /ml ((NO)-N-.) and 0.001-0.01 mu g PMA/ml (H2O2). At saturated PMA con centrations, (NO)-N-. production, oxygen uptake and H2O2 release were 0.56 +/- 0.04, 3.32 +/- 0.52 and 1.19 +/- 0.17 nmol.min(-1).10(6) cell s(-1). (NO)-N-. production accounts for about 30% of the total oxygen uptake. Luminol-dependent chemiluminescence, reported to detect NO rea ctions in other inflammatory cells, was also half-maximally activated at about 0.001-0.01 mu g PMA/ml. Preincubation with NG-monomethyl-L-ar ginine (L-NMMA) decreased O-2 uptake and (NO)-N-. release but increase d H2O2 production, while superoxide dismutase (SOD) increased (NO)-N-. detection by 30%. Chemiluminescence was also reduced by preincubation with L-NMMA and/or SOD. The results indicate that (NO)-N-. release is part of the integrated response of stimulated human neutrophils and t hat, in these cells, kinetics of (NO)-N-. and O-2(.-) release favour t he formation of other oxidants like peroxynitrite.