Synthesis of prostaglandin I2 (prostacyclin) by cultured human and bovine endothelial cells.

Cultured endothelial cells derived from human umbilical veins or bovine aorta produce a potent inhibitor of platelet aggregation. The inhibitor is synthesized from sodium arachidonate or or prostaglandin endoperoxides by a microsomal enzyme system. Tranylcypromine, a specific antagonist of prostacyclin synthetase, suppresses production of the inhibitor by endothelial cells. The inhibitor, which is ether extractable, has been identified using a two-step thin-layer radiochromatographic procedure and a synthetic prostaglandin I2 standard. With this procedure, we have shown that human and bovine endothelial cells convert sodium [3H]arachidonate to radiolabeled prostaglandin I2 and 6-keto-prostaglandin F1alpha, as wellas prostaglandin E2. Thus, endothelial cells may be non-thrombogenic in vivo because they synthesize and release prostaglandin I2, a potent inhibitor of platelet aggregation.