Islet-activating protein, pertussis toxin, inhibits Ca2+-induced and guanine nucleotide-dependent releases of histamine and arachidonic acid from rat mast cells.

Islet-activating protein (IAP) suppressed Ca2+-induced histamine release and phospholipase A2 activation in Gpp(NH)p-loaded mast cells. Since the guanine nucleotide-binding protein involved in adenylate cyclase inhibition is known to lose its function upon being ADP-ribosylated by IAP, the nucleotide-binding protein is likely to mediate Ca2+-linked biosignalling leading to histamine secretion.