Effects of calmodulin inhibitor on histamine release from rat peritoneal mast cells induced by concanavalin A and ionophore A23187.

The involvement of calmodulin in stimulus-secretion coupling of histamine release from rat mast cells was examined using a specific calmodulin inhibitor, W-7 [N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide]. W-7 at low concentrations inhibited histamine release induced by either concanavalin A or ionophore A23187 and at high concentrations enhanced the release. But its congener, W-5 [N-(6-aminohexyl)-1-naphthalenesulfonamide], which has virtually no calmodulin-inhibiting activity, did not affect the release. It is concluded that W-7 modulates histamine release by inhibiting some functions of calmodulin in the cells.