Enhancement of phagocytosis by a calmodulin antagonist (W-7) in mice

W-7 [N-(6-aminohexyl)-5-chloro-1-naphthalene sulfonamide], a well-known inhibitor of the calmodulin-dependent processes, strongly enhanced phagocytosis and ingestion of polystyrene latex beads into the peritoneal macrophages of BALB/c mice after the i.p. injection, whereas W-5 [N-(6-aminohexyl)-naphthalene sulfonamide], a less effective calmodulin antagonist, was much weaker than W-7. Binding of the third component of complement (C3) cleavage to the C3 receptor on macrophages after the i.p. injection of W-7 was enhanced as shown by the fluorescent antibody technique. These data suggest that calmodulin plays an important role in the phagocytosis of macrophages through the complement system.