RELEASE OF ARACHIDONIC-ACID VIA CA2-TUMOR CELLS( INCREASE STIMULATED BY PYROPHOSPHONUCLEOTIDES AND BRADYKININ IN MAMMARY)

The relationship between the increase of intracellular Ca2+ and the re lease 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 A(2) and W-7, a calmodulin antagonist. It is suggested that the increase in cyt osolic Ca2+-induced release of arachidonic acid occurs through activat ion of calmodulin-dependent phospholipase A(2).