Fibrinolytic system of cultured endothelial cells: regulation by plasminogen activator inhibitor.

Cultured bovine aortic endothelial cells have a relatively complex fibrinolytic system that is responsive to both the physiological state of the cell itself and to a variety of agents added to the culture medium. The fibrinolytic activity of these cells results from the production of both urokinase-type and tissue-type plasminogen activators and is regulated by an inhibitor capable of neutralizing their activities. The properties of these fibrinolytic components will be reviewed, and their respective roles in initiating and regulating the fibrinolytic activity of the cells will be summarized. A cDNA coding for the inhibitor has been isolated, and its sequence will be compared to that of other serine proteinase inhibitors.