Differences in the effect of arachidonic acid on polymorphonuclear and mononuclear leukocyte function

Incubation of human polymorphonuclear leukocytes with arachidonic acid resulted in a stimulation of the oxidative metabolism of the cells. Upon stimulation with 80 μM arachidonic acid, neutrophils (5·106 cells/ml) produced superoxide (53±8 nmol/5·106 cells per 15 min), generated chemiluminescence (1211 100±157 000 cpm) and consumed oxygen (20±1 nmol/106 cells per 5 min). The stimulation of the cell metabolism could be reduced 40–60% by prior incubation of the cells with 10 μM indomethacin. Incubating polymorphonuclear leukocytes with arachidonic acid also resulted in a diminished chemotaxis towards an attractant, a decreased uptake of opsonized staphylococci and aggregation of the cells. This may be due to inhibitory products of arachidonic acid metabolism and toxic oxygen species produced during stimulated oxidative metabolism. The effects of arachidonic acid are specific for neutrophils, as mononuclear phagocytes only produced 17±8 nmol superoxide/5·106 cells per 15 min and generated 27 000±15 000 cpm chemiluminescence when stimulated with 80 μM arachidonic acid. When monocytes and neutrophils were stimulated with particles such as opsonized staphylococci, the amount of superoxide produced, oxygen consumed and chemiluminescence generated were similar. The phagocytic activity of the monocytes was also not affected by prior incubation with arachidonic acid. We conclude that in contrast to monocytes, neutrophil metabolism can be stimulated with arachidonic acid and this stimulation resulted in a decreased phagocytic activity of these cell