EFFECTS OF ZINC ON PRODUCTION OF ACTIVE OXYGEN SPECIES BY RAT NEUTROPHILS

The effects of zinc on the production of active oxygen species were in vestigated in rat neutrophils by chemiluminescence and spectrophotomet ric assays. The luminol-dependent chemiluminescence in unstimulated ne utrophils showed a single peak. Zinc al concentrations lower than 0.1 mM augmented the intensity of chemiluminescence and showed a bimodal p attern, the first peak of which was inhibited by superoxide dismutase and catalase, while the second peak disappeared in the presence of cat alase, but was unaffected by superoxide dismutase. At the same concent rations of zinc, O-2(-) and H2O2 production increased, but secretion a nd activity of myeloperoxidase were not affected. Zinc at 0.1 mM enhan ced the second peak of luminol-dependent chemiluminescence, and concom itantly O-2(-) and H2O2 production of neutrophils stimulated with form yl-methionyl-leucyl-phenylalanine. Homogenized neutrophils showed a bi modal pattern on induction by zinc, the second peak of which was inhib ited slightly by catalase and completely by sodium azide, but was not inhibited by superoxide dismutase. Zinc-induced O-2(-) production was inhibited by pertussis toxin, but was not significantly inhibited by a protein kinase C inhibitor, 1-(5-isoquinolinesulfonyl)-2-methylpipera zine dihydrochloride (H-7), or a calmodulin antagonist, N-(6-aminohexy l)-5-chloro-1-naphthalenesulfonamide (W-7). These results suggest that zinc can augment luminol-dependent chemiluminescence by increasing O- 2(-) production through the classical signal transduction pathway, and by increasing H2O2 not via O-2(-).