Prostacyclin: Production by Vascular Endothelium and Effects on Platelet Aggregation

The inhibitory effect of vascular endothelial cells on platelet aggregation is due to their ability to release prostacyclin. The existence of an ADPase has been confirmed in endothelial cells but this enzymes does not seem to be related to the anti-aggregating properties of vascular endothelium. In vitro, the release of prostacyclin by humand and rabbit endothelial cells persists after several subcultures. The production of PGI2 can be demonstrated by its inhibition by aspirin-like drugs or 15-hydroperoxy arachidonic acid (a specific inhibitor of PGI2 synthesis). Moreover, the antiaggregating activity is antagonised by an antibody to 5,6 dihydro prostacyclin which cross reacts and neutralises prostacyclin.