Antithrombin III stimulates prostacyclin production by cultured aortic endothelial cells

Prostacyclin (PGI2) is a potent vasodilator and an inhibitor of platelet aggregation. We found that antithrombin III (AT III), an anticoagulant present in circulating blood, stimulated PGI2 production by cultured bovine aortic endothelial cells in a dose- and time-dependent manner. The stimulation of PGI2 production by AT III was observed at physiological concentrations and was inhibited by the addition of anti-AT III antiserum and heparin. These results suggest that AT III may stimulate PGI2 production by binding to heparin-like molecules on the endothelial cell membrane.