Low extracellular Mg2+ concentrations suppress phagocytosis in vitro by alveolar macrophages from rats

The aim of this study was to assess the effects of extracellular Mg2+ conce ntrations on phagocytosis in vitro by alveolar macrophages from rats. Phago cytosis was suppressed in the presence of low, but not high, Mg2+ concentra tions. Vanadate, a Mg2+-ATPase inhibitor, suppressed phagocytosis. In the p resence of a low Mg2+ concentration or vanadate, the cytosolic free Ca2+ co ncentration ([Ca2+]i) increased, but the cytosolic free Mg2+ concentration did not. These results suggest that low extracellular Mg2+ concentrations a nd vanadate suppress phagocytosis by rat alveolar macrophages by increasing [Ca2+]i.