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

Abstract

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.