Studies on a complex mechanism for the activation of plasminogen by kaolin and by chloroform: the participation of Hageman factor and additional cofactors

Abstract

A B S T R A C T As demonstrated by others, fibrinolytic activity was generated in diluted, acidified normal plasma exposed to kaolin, a process requiring Hageman factor (Factor XII). Generation was impaired by adsorbing plasma with glass or similar agents under conditions which did not deplete its content of Hageman factor or plasminogen. The defect could be repaired by addition of a noneuglobulin fraction of plasma or an agent or agents eluted from diatomaceous earth which had been exposed to normal plasma. The restorative agent, tentatively called Hageman factor-cofactor, was partially purified by chromatography and had an apparent molecular weight of approximately 165,000. It could be distinguished from plasma thromboplastin antecedent (Factor XI) and plasma kallikrein, other substrates of Hageman factor, and from the streptokinase-activated pro-activator of plasminogen. Evidence is presented that an additional component may be needed for the generation of fibrinolytic activity in mixtures containing Hageman factor, HF-cofactor, and plasminogen.The long-recognized generation of plasmin activity in chloroform-treated euglobulin fractions of plasma was found to be dependent upon the presence of Hageman factor. Whether chloroform activation of plasminogen requires Hageman factor-cofactor was not determined, but glass-adsorbed plasma, containing Hageman factor and plasminogen, did not generate appreciable fibrinolytic or caseinolytic activity. These studies emphasize the complex nature of the mechanisms which lead to the generation of plasmin in human plasma. INTRODUCTIONPlasminogen, a normal constituent of human plasma, is the precursor of plasmin, a protease of broad specificity. The conditions which lead to its activation are still uncertain. Hypotheses suggesting the existence of a physiologic blood activator of plasminogen (1, 2), whose level is enhanced by various stresses (3)(4)(5)(6)(7)(8)(9), are supported by a considerable volume of experimental evidence (10)(11)(12). The origin of this plasminogen activator is uncertain, although vascular endothelial cells have been implicated (13)..The fibrinolytic properties of normal human plasma, presumably due to the generation of plasmin, are greatly enhanced by incubation with kaolin after acidification and lowering of the ionic strength (14, 15). and Iatridis and Ferguson (15) observed that this elaboration of fibrinolytic activity was strikingly reduced in plasma deficient in Hageman factor (Factor XII) and suggested that this clotting factor had a role in the ultimate formation of plasmin. Their hypothesis has been reinforced by the finding that the expected increase in blood fibrinolytic activity in response to physical exertion (16) with that proactivator of plasminogen through which streptokinase brings about the formation of plasmin (23,24). In the present study, evidence is assembled that an activator of plasminogen can be derived from human plasma which is separable from the proactivator upon which streptokinase acts. This agent is dependent upon th...

Partial purification and characterization of contact activation cofactor.

“…Factor XIIcofactor is a plasma activity through which Factor XII can initiate fibrinolysis. It elutes from anionic exchange resins with the Factor XI fraction (19,20). In contrast, CAC is bound to the resin at low ionic strength and elutes far beyond Factor XI in the presence of much higher salt concentrations, as shown above.…”

A Prealbumin Activator of Prekallikrein

“…This activity is partially destroyed by heating for 30 rain at 56°C. Since activation of Hageman factor not only initiates the intrinsic pathway of blood coagulation (22,23) and the fibrinolytic system (24,25) but also the kinin-forming sequence, it seemed appropriate to evaluate the components of the kinin-forming system as possible contributors to the chemotactic activity of normal serum. Fractionation of normal senml on Sephadex G-200 revealed several peaks of chemotactic activity of which one coincided with the peak of kallikrein (Fig.…”

Partial Purification of Plasma Thromboplastin Antecedent (Factor XI) and its Activation by Trypsin

“…15 platelet-deficient plasma separated by two successive centrifugations at 16,300 g for 20 min each. Citrated human plasma deficient in one or another clotting factor and bovine PTA-deficient plasma (6) were obtained as described earlier (7). A standard pool of 25 normal human plasmas was prepared by an earlier method (8).…”