title: Effect of extracellular calcium on superoxide release by rat alveolar macrophages.
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.
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D002478:Cells, Cultured; D003208:Concanavalin A / Q000494:pharmacology; D004072:Digitonin / Q000494:pharmacology; D005110:Extracellular Space / Q000378:metabolism*; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D008264:Macrophages / Q000378:metabolism*; D008297:Male; D009239:N-Formylmethionine / Q000031:analogs & derivatives / Q000494:pharmacology; D009240:N-Formylmethionine Leucyl-Phenylalanine; D009842:Oligopeptides / Q000494:pharmacology; D010100:Oxygen / Q000378:metabolism*; D011650:Pulmonary Alveoli / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D013268:Stimulation, Chemical; D013481:Superoxides / Q000378:metabolism*
chemical_list: D002121:Calcium Channel Blockers; D009842:Oligopeptides; D003208:Concanavalin A; D013481:Superoxides; D009239:N-Formylmethionine; D009240:N-Formylmethionine Leucyl-Phenylalanine; D007770:L-Lactate Dehydrogenase; D004072:Digitonin; D010100:Oxygen; D002118:Calcium