Thromboplastic and fibrinolytic activities were estimated in layers of rabbit aortae and vena cavae, using the chromogenic peptide substrate method. Thromboplastic activities seemd to be localized, in aortae, mainly in the adventitia. The endothelium was moderately active. In aortae and the inferior vena cava, the subendothelium with the media seemed to have a higher plasminogen activator activity than other layers. These data indicate that activation of the extrinsic and fibrinolytic systems is easily induced by vascular injuries.
Human citrated plasma was placed on the de-endothelialized surface of rabbit thoracic aorta fixed in Petri dishes and, after rotation at 4-10°C for 10 or 30 min, time dependent decline of the levels of plasma prekallikrein and of the α₂-plasmin inhibitor took place, which appeared to be closely associated with contactactivation of the intrinsic system.
Various coagulo-fibrinolytic activities were observed using the fibrin plate method in citrated plasma obtained from 40 diabetics. High levels of VIII R: Ag, VIII R: WF, VIII: C, F XII and HMW-kininogen were found in all the diabetics. The levels of the former two originating from the blood vessel were especially high in the group of diabetics with microangiopathy, who revealed an increased fibrinolytic activity, as tested after venous stasis.
Thus, activating and inhibiting vascular factors may influence intravascular coagulofibrinolysis induced by vascular injuries.