Discrepancies in the oxygen balance of whole human neutrophils and neutrophil homogenates.

Abstract

The oxygen consumption, superoxide production and hydrogen peroxide generation was studied in human neutrophils phagocytosing zymosan particles. Application of sodium azide, as an inhibitor of catalase, and/or 1,3-bis(chloroethyl)-1-nitrosourea (BCNU), as an inhibitor of glutathione reductase, led to the conclusion that neutrophils convert about half of the oxygen consumed in the respiratory burst to hydrogen peroxide; the other half is used for formation of organic peroxides, disulfide bridges, etc. These products are rapidly degraded to water by catalase and/or the glutathione redox cycle. Reduction of exogenous cytochrome C accounted for only about 15% of the consumed oxygen. Neutrophil homogenates contain a badly damaged oxidase system, because oxygen consumption and hydrogen peroxide formation were only about one-tenth of that observed with whole cells. In contrast, cytochrome-C reduction was about three times as high as that found with intact cells. Probably, cytochrome C partly reconstitutes damaged oxidase systems, thus artificially increasing the oxidase activity. We conclude that cytochrome-C reduction is not a good parameter to characterize cell-free oxidase preparations.