Release of arachidonic acid via Ca2+ increase stimulated by pyrophosphonucleotides and bradykinin in mammary tumour cells

The relationship between the increase of intracellular Ca2+ and the release of arachidonic acid by bradykinin and pyrophosphonucleotides was studied in cultured mammary tumour cells, MMT060562. Bradykinin, ATP, UTP and UDP induced an increase of intracellular Ca2+ and the release of arachidonic acid from phospholipids into the extracellular fluid. Release of arachidonic acid was also induced by the application of the Ca2+ ionophore, A23187. Liberation of arachidonic acid by bradykinin and ATP was reduced by mepacrine, a blocker of phospholipase A2 and W-7, a calmodulin antagonist. It is suggested that the increase in cytosolic Ca2+-induced release of arachidonic acid occurs through activation of calmodulin-dependent phospholipase A2.