Oxygen consumption by stimulated human neutrophils

Oxygen consumption by stimulated human neutrophils has been studied. An initial lag after stimulation of about 20 s is followed by a linear phase of oxygen consumption which lasts about 60 s and then declines exponentially. The duration of the respiratory burst is thus much shorter than has been generally recognized. The cessation of the linear phase of oxygen consumption occurs at a constant time after stimulation, is not due to depletion of the substrate of the oxidase enzyme (since linear oxygen consumption can be re-initiated), and is due to termination or saturation of particle uptake. The curtailment of oxygen consumption probably marks the end of the oxygen-dependent microbial role of the phagocytic vacuole, preparing it for the secondary and independent function of digestion. A novel cytochrome b becomes associated with the phagosomes and probably forms a component of a complex electron-transport chain. Superoxide may be an intermediate in this system, but it is unlikely to be released free from the cell or to form the final product of the system.