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.