Calcium ionophore A 23187 induces arachidonic acid release from phosphatidylcholine in cultured human endothelial cells

Cultured endothelial cells from human umbilical vein were incubated with (³H)arachidonic acid for 24 hours. The label was incorporated into phospholipids (79.3 %), neutral lipids (15.6 %) and non-esterified fatty acids (4.7 %). Upon challenge with the calcium ionophore A 23187, 5.3 % of the total radioactivity were found in supernatant and corresponded to 6-keto-prostaglandin F_1α (1.6 %) and free arachidonic acid (3.7 %). This release was accompanied by a concomitant and selective decrease of phosphatidylcholine. It is concluded that the entry of calcium promoted by A 23187 activates a phospholipase A₂ regulating the availability of arachidonic acid to the prostacyclin synthetase.