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  • Title: Superoxide generation and granule enzyme release induced by ionophore A23187. Studies on the early events of neutrophil activation.
    Author: Simchowitz L, Spilberg I, Atkinson JP.
    Journal: J Lab Clin Med; 1980 Sep; 96(3):408-24. PubMed ID: 6156974.
    Abstract:
    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.
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