Superoxide generation and granule enzyme release induced by ionophore A23187. Studies on the early events of neutrophil activation.
The responses of isolated human peripheral neutrophils to activation by the divalent cation ionophore A23187 (4 x 10(-8) M to 2 x 10(-5) M) were studied over the course of 15 min at 37 degrees C. Dose-dependent increases were noted in the following A23187-induced functions: (1) membrane depolarization, as assessed by a fluorescent cyanine dye, (2) altered membrane permeability to 22Na+ and 45Ca2+, (3) increased intracellular levels of cAMP, (4) O2-generation, and (5) granule enzyme release. Membrane depolarization and the cAMP response preceded the onset of O2- generation and exocytosis, which began after a latency period of approximately 30 sec. All five functions induced by 2 x 10(-5) M A23187 required approximately 1 mM Ca0 for optimal expression and declined substantially as Ca0 was reduced towards a nominal O mM. In contrast, the Na+ ionophore gramicidin D (0.1 to 10 microgram/ml) caused cell depolarization and increased 22Na+ ionophore gramicidin D (0.1 to 10 microgram/ml) caused cell depolarization and increased 22Na+ uptake but did not stimulate 45Ca2+ uptake, the cAMP response, O2- generation, or exocytosis of granule constituents. The observations dissociate membrane depolarization and altered Na+ permeability, on the one hand, from a Ca2+ influx, cAMP response, O2- release, and exocytosis on the other. These studies, then, are consistent with a hypothesis that a Ca2+ influx is required for the biologic expressions of cell activation.
D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D000001:Calcimycin / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism; D000242:Cyclic AMP / Q000096:biosynthesis; D006152:Cyclic GMP / Q000096:biosynthesis; D003594:Cytoplasmic Granules / Q000201:enzymology*; D004305:Dose-Response Relationship, Drug; D006096:Gramicidin / Q000494:pharmacology; D006801:Humans; D008856:Microscopy, Fluorescence; D009504:Neutrophils / Q000502:physiology*; D010100:Oxygen / Q000096:biosynthesis*; D012964:Sodium / Q000378:metabolism; D013481:Superoxides / Q000096:biosynthesis*; D013997:Time Factors
D000900:Anti-Bacterial Agents; D013481:Superoxides; D006096:Gramicidin; D000001:Calcimycin; D012964:Sodium; D000242:Cyclic AMP; D006152:Cyclic GMP; D010100:Oxygen; D002118:Calcium