On the nature of fibrinolytic activity of arteries.

The plasminogen activator of the arterial wall was studied with the histochemical method of TODD. The plasminogen activator was removed from the sections after extraction with M-potassium thiocyanate. By this procedure we suggest that the activator demonstrated by the histochemical method is the same substance as that prepared by the extraction method with thiocyanate of ASTRUP and STAGE. However, a new fibrinolytic activity was restored after treatment of these extracted sections with streptokinase or urokinase. There were no differences in the different types of arteries examined and normal or atherosclerotic arteries. Similar findings were found when kidney or myocardial tissues were examined. It is suggested that the arterial and other tissues contain proactivator-plasminogen which is not extracted from the tissue by potassium thiocyanate and can adsorb streptokinase or urokinase.