Receptor-mediated activation of arachidonic acid release in mouse peritoneal macrophages is linked to extracellular calcium influx

The role of external calcium in platelet-activating factor- and zymosan-stimulated arachidonic acid release from mouse macrophages was investigated. Deprivation of external Ca2+ led to strong inhibition of receptor-mediated arachidonic acid release, which was completely restored when Ca2+ was added to the incubation medium. When arachidonic acid release was examined in Ca(2+)-depleted cells, the response took place only in presence of external Ca2+. Verapamil, a voltage-dependent Ca2+ channel blocker, nearly abolished arachidonic acid release in response to both platelet-activating factor and zymosan. These results suggest that extracellular Ca2+ influx is functionally linked to arachidonic acid release and hence to phospholipase A2 activation in mouse peritoneal macrophages.