SUPEROXIDE GENERATION AND GRANULE ENZYME-RELEASE INDUCED BY IONOPHORE A23187 - STUDIES ON THE EARLY EVENTS OF NEUTROPHIL ACTIVATION

  • 1 January 1980
    • journal article
    • research article
    • Vol. 96  (3) , 408-424
Abstract
The responses of isolated human peripheral neutrophils to activation by the divalent cation ionophore A23187 (calcimycin) at doses of 4 .times. 10-8 M to 2 .times. 10-5 M were studied over 15 min at 37.degree. C. Dose-dependent increases were noted in the following A23187-induced functions: membrane depolarization, as assessed by a fluorescent cyanine dye, altered membrane permeability to 22Na+ and 45Ca2+, increased intracellular levels of cAMP, O2- [superoxide] generation and 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 s. All 5 functions induced by 2 .times. 10-5 M A23187 required .apprx. 1 mM Ca0 [extracellular Ca2+ concentration] for optimal expression and declined substantially as Ca0 was reduced towards a nominal 0 mM. The Na+ ionophore gramicidin D (0.1-10 .mu.g/ml) caused cell depolarization and increased 22Na+ uptake but did not stimulate 45Ca2+ uptake, the cAMP response, O2- generation, or exocytosis of granule constituents. These observations dissociate membrane depolarization and altered Na+ permeability from Ca2+ influx, cAMP response, O2- release and exocytosis. The hypothesis that a Ca2+ influx is required for the biologic expressions of cell activation is supported.