Institute of Anatomy, Saarland University, Kirrberger Str. 100, 66424 Homburg/Saar Germany
Background: The influence of extracellular calcium on phagocytosis is limited, and the involvement of extracellular magnesium is unclear. Aims: The role of extracellular calcium and magnesium on phagocytosis efficiency was investigated. Results: Extracellular calcium had no influence on the internalization of 1 μm polystyrene particles by primary monocytes as has been shown before for the human lymphoma-derived, differentiated cell line U937 and murine alveolar macrophage-derived MH-S cells. In contrast, the phagocytosis by differentiated U937 cells was positively affected by the presence of extracellular magnesium whereas that of MH-S cells was not. An extracellular increase in the magnesium level did not cause an increase in the free cytosolic magnesium concentration in either cell line. In contrast to magnesium, extracellular calcium caused an increase in intracellular divalent cation levels in differentiated U937 cells. Conclusions: A phagocytosis-enhancing effect in the extracellular space was observed in relation to extracellular magnesium rather than with an intracellular increase in magnesium levels, indicating that murine and human immune cells might be regulated differently.