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  • Title: Effect of extracellular calcium on superoxide release by rat alveolar macrophages.
    Author: Forman HJ, Nelson J.
    Journal: J Appl Physiol Respir Environ Exerc Physiol; 1983 May; 54(5):1249-53. PubMed ID: 6305896.
    Abstract:
    Alveolar macrophages can be stimulated to release superoxide into the extracellular medium. The mechanism of activation of superoxide release has been reported to be mediated by the movement of Ca2+ into the cytosol, but the involvement of extracellular Ca2+ in this process has remained uncertain. Extracellular Ca2+ was not an absolute requirement for activation of superoxide release; however, 1.3 mM extracellular Ca2+ caused an approximate twofold enhancement of superoxide release stimulated by either concanavalin A or formyl-methionyl-leucyl-phenylalanine but had no effect on digitonin-stimulated superoxide release. Concanavalin A-stimulated superoxide was inhibited by the "Ca2+ entry blockers," Mn2+ (1 microM) or methoxyverapamil (D-600) (100 microM). Inhibition by Mn2+ was competitive with extracellular Ca2+, whereas inhibition by D-600 was noncompetitive. Neither inhibitor, however, affected superoxide release after initiation. Thus activation of superoxide release by alveolar macrophages can be accomplished, in part, through the entrance of Ca2+ into the cell.
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