Effects on extra- and intracellularly localized, chemoattractant-induced, oxygen radical production in neutrophils following modulation of conditions for ligand-receptor interaction.

Results obtained with the luminol-dependent chemiluminescence (CL) technique show that with this technique, generation of oxygen radicals from an extra- as well as from an intracellular source is quantified. This investigation was performed in order to study the relationship between intra- and extracellularly generated radicals in human granulocytes stimulated with the chemoattractant formyl-methionyl-leucyl-phenylalanine (FMLP). A difference in time course between extra- and intracellular CL was observed. The extracellular response reached a maximum value after 1-2 min, whereas the intracellular response reached a maximum value after 5-7 min. The ED50 values for the two responses were the same, whereas the onset time was a little longer for the intracellular response. Both high and low concentrations of FMLP gave rise to CL. However, the ratio between the extra- and the intracellular response differed depending on the concentration of FMLP; the ratio was decreased at low concentrations of FMLP. The same type of change was obtained when the ligand-receptor ratio was decreased through modulation of the number of exposed receptors. The ratio between extra- and intracellular activities was also changed by cytochalasin B, removal of Ca2+, or removal of Na+. The role of the extra- and intracellular oxygen radical production as well as possible regulatory mechanisms are discussed.