Difference in changes of membrane fluidity of polymorphonuclear leukocytes stimulated with phorbol myristate acetate and formyl-methionyl-leucyl-phenylalanine: role of excited oxygen species.

Polymorphonuclear leukocytes (PMN) were stimulated with phorbol myristate acetate (PMA) and N-formyl-methionyl-leucyl phenylalanine (FMLP) to clarify the role of excited oxygen species in inducing changes of membrane fluidity. Membrane fluidity was assessed by the excimer-forming lipid technique using pyrenedecanoic acid and flow cytometry. Membrane fluidity of PMN decreased following stimulation with PMA, and the extent of decrease was both time- and dose-dependent. FMLP at 10(-5) M induced a decrease, while FMLP at 10(-7) M induced a rapid increase. On stimulation with 10(-7) M FMLP as well as in a resting condition, the change of membrane fluidity of PMN from patients with chronic granulomatous disease (CGD) was similar to that of normal PMN. However, on stimulation with PMA or 10(-5) M FMLP, CGD PMN did not show a significant decrease. In addition, normal PMN incubated with catalase inhibited the decrease. These findings suggest that the generation of excited oxygen species, particularly of H2O2, is important in inducing a decrease of PMN membrane fluidity.