Components Of Fibrinolytic System Research Articles

Unbalanced Coagulation-Fibrinolysis Potential during L-Asparaginase Therapy in Children with Acute Lymphoblastic Leukaemia

Treatment of acute lymphoblastic leukaemia (ALL) with L-asparaginase (L-asp) may be associated with thrombotic complications, but the pathogenetic mechanisms of thrombus formation and persistence remain unclear. We studied the procoagulant activity (PCA) of peripheral blood mononuclear cells and some components of the plasma fibrinolytic system in 10 children with ALL undergoing remission induction therapy which includes L-asp. Mononuclear cells obtained 14 days after starting L-asp treatment generated significantly higher amounts of PCA (identified as tissue factor) than cells isolated before the first dose of L-asp and 7 days after the cessation of L-asp administration (p less than 0.01). Augmented PCA coincided with an increase in the plasma D-dimer. The plasma levels of type 1 plasminogen activator inhibitor were found significantly elevated during L-asp therapy (p less than 0.05), whereas plasminogen levels were markedly decreased (p less than 0.05). These findings suggest that, during the course of L-asp treatment, the coagulation-fibrinolysis balance is shifted towards promotion of fibrin formation and deposition. Although it remains to be conclusively established whether L-asp per se or the concurrent administration of multiple chemotherapeutic agents is responsible for these changes, the latter could contribute to the thrombotic complications associated with remission induction therapy for ALL.

Inhibition of fibrinolysis by cellular glutathione depletion in the rabbit

The effect of cellular glutathione depletion on fibrinolytic activity in the arterial wall and on the levels of components of the plasma fibrinolytic system was studied in rabbits. Intraperitoneal administration of buthionine sulphoximine (4.5 mmol/kg body wt), an inhibitor of gamma-glutamyl cysteine synthetase, induced a significant reduction in liver glutathione concentrations with a peak decrease of 51% at 7 hours and a progressive return to normal values. The glutathione concentration in aortic tissue was also significantly reduced 7 h after administration of the depleting agent. Fibrinolytic activity in the arterial wall was inhibited following buthionine sulphoximine administration and only reappeared at 24 hours postinjection. Diethyl maleate administration (3.2 mmol/kg body wt i.p.) also depleted liver and aortic glutathione and inhibited fibrinolysis in the arterial wall. Treatment with both glutathione-depleting agents induced a significant reduction in the functional activity of tissue plasminogen activator (t-PA) (-61% and -27% respectively for buthionine sulphoximine or diethyl maleate) and a significant increase in that of plasminogen activator-inhibitor (PAI) (+61% and +27% respectively), while alpha-2-antiplasmin activity was not modified. Our data suggest a modulatory role of glutahione in the release and/or clearance of the components of the fibrinolytic system in the rabbit.

The rabbit as a model for studies of fibrinolysis

When compared to man, the rabbit shows marked prolongation of the dilute whole blood clot lysis time and an attenuated increase in plasminogen activator (PA) after the infusion of desmopressin (DDAVP). The levels of specific components of the plasma fibrinolytic system of the rabbit were compared to those in human plasma to ascertain their role in the differences between species. PA activity and plasminogen levels were similar in the two species. Anti-plasmin and plasminogen activator inhibitor (PAI) activity were lower in the rabbit than in man. The rabbit PAI, apparently similar to that described in man, was not increased by DDAVP infusion. The disparity between man and rabbit with respect to the lysis times of dilute blood clots and response to DDAVP cannot be explained by differences in functional plasma levels of inhibitors or activators of the fibrinolytic system.

Methods for studying fibrinolytic pathway components in human plasma

Methods have been developed to quantitatively measure the major plasma components of the human fibrinolytic system. Plasminogen is measured functionally with a 9M excess of streptokinase and immunochemically by rocket immunoelectrophoresis; the normal range was found to be 16.7–23.8 mg/dl and 17.4–21.6 mg/dl, respectively. α 2-plasmin inhibitor is measured functionally and immunochemically; the normal range for the major plasma plasmin inhibitor was found to be 5.30–6.60 mg/dl by both methods. Plasminogen activator concentrations, as well as, free, and complexed, protease activities are measured along with plasmin generation rates by spectrophotometric assays with chromogenic substrates. Both activator and free protease activities are zero in plasma samples from normal human subjects. Plasmin generation rates are 0.25–0.47% with urokinase and 5.30–9.70% with streptokinase; these values are the percentages of the respective initial velocities of activation in purified systems.

Effect of myocardial infarction on components of fibrinolytic system.

A systematic investigation of the fibrinolytic system during the period after acute myocardial infarction in 42 patients showed a progressive reduction of fibrinolytic activity, with the longest lysis times on days 4 to 5 after the event. There is a concomitant rise in the levels of fibrinogen, plasminogen, and antiplasmin; only the latter parallels the delay in lysis. After 12 to 15 months, normal lysis times and fibrinogen levels were found in 24 patients re-examined. It is concluded that the reduced fibrinolytic activity in these patients was a transient phenomenon after myocardial infarction.

Studies on the blood fibrinolytic system in congestive cardiac failure.

1. The major components of the blood fibrinolytic enzyme system were measured in patients with congestive cardiac failure, in control patients with heart disease but not in failure, and in control subjects without heart disease. 2. Heart disease in the absence of failure was associated with an increase in fibrinogen, fibrin degradation products and α1-antitrypsin, but not with any alteration of plasminogen activator, plasminogen, the serum inhibitor of plasminogen activation or α2-macroglobulin. 3. Compared with patients with heart disease, there were decreased amounts of plasminogen activator and plasminogen and increased amounts of the serum inhibitor of plasminogen activation and the antiplasmin α1-antitrypsin in patients with cardiac failure. Fibrinogen, fibrin degradation products and α2-macroglobulin were not significantly altered. 4. Plasminogen activator as measured by the euglobulin lysis time correlated inversely with the height of the jugular venous pressure, but not with liver size, the extent of oedema, chest X-ray appearances, amounts of blood urea or bilirubin. 5. The release of plasminogen activator in response to venous stasis was decreased in patients with cardiac failure.

A purified procoagulant enzyme from the venom of the eastern diamondback rattlesnake (Crotalus adamanteus): in vivo and in vitro studies.

Abstract A procoagulant enzyme in the venom of the eastern diamondback rattlesnake, Crotalus adamanteus , has been isolated and purified. The enzyme acts directly on purified fibrinogen or fibrinogen in plasma, forming a friable fibrin clot. The enzyme does not activate factors of the extrinsic system, nor does it activate factor XIII. It also does not aggregate platelets and is not inhibited by heparin. Incubation with plasma produces insignificant changes in all coagulation factors except fibrinogen. The enzyme does not activate components of the fibrinolytic system, but is itself fibrinolytic at extremely high concentration. Infusion into dogs produces well tolerated hypofibrinogenemia lasting up to 8 hours. Post infusion, intense fibrinolysis is observed with high titers of nonclottable fibrinogen derivatives in the serum, some with an electrophoretic mobility similar to native fibrinogen. Following infusion declines in factors II, V, and VIII were noted by one stage assays, but may be artifactual due to high levels of fibrinogen derivatives in the test plasmas.

The fibrinolytic enzyme system in hepatic cirrhosis and malignant metastases.

Components of the blood fibrinolytic system were measured in 18 patients with hepatic cirrhosis, in two patients with acute hepatic necrosis, and in 10 patients with hepatic metastases. The frequency of an elevation of plasminogen activator and a reduction in plasminogen in hepatic cirrhosis has been confirmed. Patients with compensated cirrhosis had low levels of the serum inhibitor of plasminogen activation while those with severe hepatic insufficiency or coma due to cirrhosis or hepatic necrosis had elevated levels. The presence of hepatic metastases was associated with reduced plasminogen activator levels and an increase in the fibrinogen concentration.

The effect of prolonged exercise on the components of the blood fibrinolytic enzyme system.

1. The levels of the blood components of the fibrinolytic enzyme system were measured before, during and after a 4 hr period of exercise in eight subjects.2. Mean plasminogen activator level rose progressively over the first 3 hr with little further change during the 4th hr of exercise. Following the period of exercise there was a rise in a circulating anti-activator which was still present 20 hr after completion of the exercise.3. There was no alteration in the mean blood level of plasminogen, fibrinogen, anti-plasmin or a serum inhibitor of plasminogen activation during or following the exercise.4. The significance of the findings in relation to the mechanism of interaction of the components of the fibrinolytic system is discussed.

Comparison of In Vivo Effects on Components of the Canine Fibrinolytic Enzyme System of AMCHA Fed at Varying Dose Levels

SummaryDogs were fed varying levels of trans-AMCHA (trans-4-aminomethyl-cyclohexane-1-carboxylic acid), a known inhibitor of the fibrinolytic enzyme system. Evidence that dialysis against citrate-veronal buffer in the cold for 24 hrs effectively removes AMCHA from plasma is presented. Determinations of antiactivator, antifibrinolysin, and proactivator were carried out on both dialyzed and undialyzed samples. At 55 mg/kg, a moderate immediate decrease in urokinase excretion occurred which was maintained throughout the time of drug administration. At higher levels, increases in antiactivator and decreases in proactivator and euglobulin lytic activity occurred, the extent of which could be roughly correlated with the amount of drug administered. No changes in either fibrinogen or antifibrinolysin were seen. An assay for the antiurokinase activity in canine plasma is described. The results are discussed in terms of the possible function of the fibrinolytic system as revealed by administration of inhibitors.

Changes in the fibrinolytic system components during extracorporeal circulation.

Changes in the fibrinolytic system components during extracorporeal circulation.

Streptokinase as a thrombolytic agent

E XTENSIVE clinical studies in manycenters have indicated the thrombolytic potential of various intravenously infused plasmin preparations. Interpretations of these clinical studies are complicated by (1) wide variations in the natural course of disease; (2) an antiinflammatory effect which may follow clinical use of the enzymes; and (3) inadequate definition and standardization of these plasmin preparations containing varying amounts of streptokinase, streptokinase-activated plasminogen as the activator complex, and streptokinaseactivated plasminogen as plasmin. In the present studies, forty-one experimental thrombi, 2 to 5 inches long, were induced in the superficial veins in the arms and legs of human volunteers by direct irritation of the intima with a dental broach or by chemical irritation with sodium morrhuate. The position and size of the thrombi were determined by clinical observation and by venograms. Various ~brinolytic systems were then produced by infusing streptokinase (SK) into a contralateral extremity at varying time intervals after formation of clots. Similar studies were also made on a patient with a fibrinolytic system due to circulating endogenous activator. Thus, objective comparison was made of the various methods to produce thrombolysis and to prevent reformation of the thrombi. Three different systems were established by varying the amount of SK infused : (1) moderate amounts of circulating plasmin with no measurable free SK (method P) ; (2) negligible plasmin with moderate amounts of free SK or activator (method SK) ; and (3) small amounts of both free SK and plasmin (method SK-P). Thrombolysis was also tested in a fourth system, moderate amounts of endogenous activator with negligible amounts of plasmin (method A). These systems were produced and utilized under rigidly controlled biochemical conditions, each system representing a different, sharply defined agent for the production of thrombolysis. Since circulating SK in human plasma could not be distinguished by assay from the activator complex of SK-plasminogen under these experimental conditions, the use of endogenous human activator also aided in the evaluation of the SK-activator complex as a thrombolytic agent. Figure 1 represents most of the important components of the human fibrinolytic system. The kinases from tissue, plasma or streptokinase appear to react stoichiometrically with a proenzyme in plasminogen to form an activator complex.1-3 This complex, designated “activator,” or the naturally occurring activator in urine, plasma or tissues, reacts catalytically with plasminogen (the proteolytic precursor) to form a proteolytic enzyme, plasmin.*,” The plasmin in turn acts upon fibrin, fibrinogen and other proteins to produce soluble split products of these native proteins. In order to produce pathologic fibrinolysis in man, this proteolytic system must be uninhibited. Normally, there may be interference with the system at three levels. Streptokinase may be neutralized 1:’ _ a specific antibody and by less specific inhtbltorsfi Activator may be neutralized by inhibitors found primarily in the alpha-2 globulin fraction of

Evidence for the adsorption upon erythrocytes of urokinase and other components of the fibrinolytic system

Erythrocytes can adsorb urokinase, a urinary activator of plasma profibrinolysin, and protect it from plasma inhibitors. Adsorption of components of the plasma fibrinolytic system is affected by the fibrinolytic status of the animal from which the erythrocytes and plasma are obtained. The findings suggest that erythrocytes may play a role, heretofore unrecognized, in the development of fibrinolytic activity in vivo.

The Effect of Heparin on Components of the Human Fibrinolytic System

Abstract It was demonstrated with human urokinase, human fibrinolytic euglobulins and human pyrogen plasma as enzyme source, and with bovine fibrin plates and human plasma plates as substrate, that high heparin concentrations inhibit fibrinolysis of preformed fibrin, in contrast to small ones which may enhance this phenomenon, provided albumin is present. No interference could be observed in the absence of plasma, serum or albumin fraction. Albumin or substances associated with the albumin fraction are required for interference of heparin with fibrinolysis. This interference probably takes place with the action of plasmin on fibrin.

Methods for measuring the activity of components of the streptococcal fibrinolytic system, and streptococcal desoxyribonuclease: Christensen, L. R.: J. Clin. Investigation 28:163 (jan.), 1949

Methods for measuring the activity of components of the streptococcal fibrinolytic system, and streptococcal desoxyribonuclease: Christensen, L. R.: J. Clin. Investigation 28:163 (jan.), 1949