Ca2+ Flux as an Initial Event in Phagocytosis by Rat Kupffer Cells

Ca2+ uptake by monolayer cultures of rat Kupffer cells was strongly stimulated immediately after contact with phagocytosable material, e.g. zymosan particles. The intensity of the luminol‐mediated chemiluminescence following zymosan addition was dependent on extracellular Ca2+; addition of the Ca2+‐ionophore A 23187 did not further increase the zymosan‐elicited response. The superoxide‐mediated chemiluminescence was not inhibited by indomethacin but could be suppressed by compounds known to inhibit Ca2+‐calmodulin‐dependent reactions. Analysis of their efficiency, however, suggests that the O−2 production is mediated by Ca2+ rather than Ca2+‐calmodulin and that the inhibitors exert another, e.g. membrane‐directed influence.