Plasmin-antiplasmin Research Articles

Activation of coagulation and fibrinolysis in acute or chronic coronary artery disease

Thrombin- and plasmin-related indices were measured in peripheral blood of 50 patients at the onset of acute myocardial infarction (AMI) and 35 chronic stable angina (CSA) patients to establish which are most indicative of acute occlusive coronary thrombosis. AMI compared with CSA had significantly higher plasma prothrombin fragment F1.2, thrombin-antithrombin III (TAT) and plasmin-antiplasmin (PAP) complexes (direct indices), but similar soluble fibrin and D-dimer levels (indirect indices). F1.2, TAT and PAP were > the 90th percentile of CSA levels in 15, 10 and 29 AMI patients, respectively. Thus, direct indices of thrombin and plasmin formation appear more indicative of acute coronary thrombosis than indirect ones. In AMI, raised F1.2, TAT and PAP in only some patients is consistent with wide variability in the activity of the underlying thrombotic process.

Posttrauma coagulation and fibrinolysis

To determine the effects of disseminated intravascular coagulation (DIC) and head injury on posttrauma coagulation and fibrinolysis. Case-control study. General ICU (tertiary care center) in a city hospital serving a population of 150 million people. Forty trauma victims: 15 with DIC; 25 without DIC. Measurement of six types of coagulation and fibrinolytic molecular markers (fibrinopeptide A, fibrinopeptide B beta 15-42, plasmin antiplasmin complex, D-dimer, tissue plasminogen activator antigen concentration, tissue plasminogen activator activity) immediately after trauma, 3 days later, and 6 days later. Anticoagulant treatment with gabexate mesilate at 1.45 +/- 0.06 mg/kg/hr. Fibrinopeptide A, fibrinopeptide B beta 15-42, plasmin antiplasmin complex, and D-dimer showed high values immediately after trauma and exceeded normal activity for the first 6 days. When trauma was complicated with DIC, the molecular markers showed significantly higher values than those for non-DIC patients on all days. In the head-injured patients, such effect was not noted. Tissue plasminogen activator antigen concentration and tissue plasminogen activator activity were within a normal physiologic range of variation. By contrast, tissue plasminogen activator antigen concentration increased significantly after trauma in patients with DIC. When anticoagulant treatment was found effective, it caused a reduction in fibrinopeptide A. a) Fibrinolytic shut-down and its reactivation cannot be confirmed after trauma. b) Head injury does not lead to an increase in posttrauma coagulation or fibrinolytic activity. c) DIC enhances posttrauma coagulation and fibrinolytic activity and plasminogen activator inhibitor activity can be inferred in DIC patients. d) Increase in tissue plasminogen activator antigen concentration without tissue plasminogen activator activation may be a prognostic factor indicative of DIC and its chances of improvement, and fibrinopeptide A as an assessment criterion for the effectiveness of anticoagulant treatment.

Fibrin formation on vessel walls in hyperplastic and malignant prostate tissue

To explore mechanisms of coagulation activation in adenocarcinoma of the prostate, the occurrence and distribution of components of coagulation and fibrinolysis pathways in situ were studied by means of immunohistochemical techniques applied to frozen sections of fresh malignant and benign hyperplastic prostatic tissue obtained at transurethral resection. Fibrinogen was distributed throughout the perivascular and tumor connective tissue in both malignant and benign disease but was not present in adjacent areas of normal prostate. Antibodies specific for fibrin and D-dimer crosslink sites stained vascular endothelium focally in both malignant and benign tissues. Both neoplastic cells and benign hyperplastic glandular epithelial cells stained weakly and in a patchy distribution for tissue factor and focally for low-molecular-weight urokinase-type plasminogen activator. Focal staining of vascular endothelium was also observed for tissue plasminogen activator and plasmin-antiplasmin complex neoantigen. By contrast, no tissue staining was observed for factor VII, factor X, factor XIII "a" subunit, high-molecular-weight urokinase-type plasminogen activator, plasminogen activator inhibitors 1 to 3, protein C, and protein S. Thus, the similarity in findings between benign hyperplastic and neoplastic prostate tissue, the lack of either an intact tumor cell-associated coagulation pathway or fibrin formation, and the presence of fibrin on vascular endothelium are consistent with the concept that coagulation activation in prostatic cancer may not be due to a direct effect of the tumor cells on the clotting mechanism. Rather, such activation may be induced by a soluble tumor product that activates procoagulant activity on certain host (for example, vascular endothelial) cells. These findings, together with the lack of effect of warfarin anticoagulation on the clinical course of patients with prostatic cancer, contrast with findings in certain other tumor types and suggest that coagulation activation may not contribute to progression of adenocarcinoma of the prostate.

Purification and characterization of human antiplasmin, the fast-acting plasmin inhibitor in plasma.

A simple and rapid purification procedure for antiplasmin is described using affinity chromatography on plasminogen-Sepharose, ion-exchange chromatography on DEAE-Sephadex and chromatography on Concanavalin-A-Sepharose. The final product was shown to be homogeneous using several polyacrylamide gel electrophoretic systems. It is a single-chain glycoprotein with a molecular weight of about 70000 as determined both by dodecyl sulphate/polyacrylamide gel electrophoresis and by sedimentation equilibrium analysis. The sedimentation constant was estimated to be 3.45 S and the carbohydrate content about 14%. Sequence analysis showed the NH2-terminal amino acid sequence to be: Asn-Gln-Glu-Gly-. Immunochemically this protein is different from all the known protease inhibitors in plasma. It was also shown that antiplasmin is a very stable protein if the pH is kept above 6. Antiplasmin rapidly forms a very stable complex with plasmin. Reduction of the complex shows that it is the B-chain of plasmin which is involved. The purified partially reduced and S-carboxy-methylated B-chain of plasmin can also progressively form a complex with antiplasmin. If the reaction between plasmin and antiplasmin is studied in an excess of plasmin a peptide bond seems to be clipped somewhere in the complex between the plasmin B-chain and antiplasmin leading to release of a 14000-Mr fragment (after reduction). This is, however, an event which occurs after complex formation.

A latex agglutination test for rapid quantitative estimation of the plasmin-antipalsmin complex in human plasma.

An antiserum was raised in rabbits against human plasmin-antiplasmin complex and rendered specific for neoantigens of this complex by absorption with purified plasminogen and plasma. Polystyrene particles were coated with the specific antibodies and used in an agglutination test for the determination of plasmin-antiplasmin complex in the plasma from various patients. Purified plasmin-antiplasma complex at a concentration of 0.1-0.2 mg/l was found to cause a clear agglutination of the particles. Activation of fresh human plasma with urokinase caused progressive generation of agglutinating activity up to a plasma dilution of 1/480. Intravenous infusion of streptokinase into patients resulted in an increase of the plasmin-antiplasmin titre of at least 1/240. Sera from patients with rheumatoid factor also agglutinated the particles but this activity could be removed by absorbing rheumatoid factor on insolubilized human IgG. Out of 101 male and twenty-three female control subjects, only three men had a plasmin-antiplasmin titre above 1/16. Of 230 hospitalized patients, plasmin-antiplasmin titres of 1/40 or more were detected in twenty-five patients. Most of these patients had diseases which are frequently associated with in vivo coagulation or fibrinolysis, but among them there was only one who showed diffuse intravascular coagulation detectable by classical methods. In the absence of an increased plasmin-antiplasmin titre none of the haemostasis analyses were indicative of in vivo coagulation or fibrinolysis. Seven out of eight patients with diffuse intravascular coagulation of various origin had plasmin-antiplasmin titres of 1/80 or 1/160. Thus, the present latex agglutination test, owing to its simplicity and sensitivity, appears to be a practical routine screening test for detecting fibrinolytic activation in plasma.

FIBRINOLYTIC INHIBITORS IN HUMAN RETROPLACENTAL BLOOD

Fibrinolytic inhibitors of plasminogen activation (urokinase inhibitors) and of plasmin (alpha2-macroglobulin, antiplasmin and total antitrypsin activity) were measured in retroplacental blood and compared with that in placental extract and maternal venous blood obtained at 40 deliveries. In placental extract the concentration of inhibitors of plasminogen activation was extremely high. In contrast, it was found to be normal in retroplacental blood and close to the value found for maternal venous blood. It therefore seems unlikely that inhibitors from the placenta enter the bloodstream and contribute to the reduction of the fibrinolytic activity in the maternal circulation during pregnancy.

The signficance of fibrinolysis. The significance of the fibrinolytic mechanism.

The fibrinolytic mechanism is assumed to remove formed fibrin from within blood vessels and the tissues, and to play an important role in maintaining vascular patency in balance with blood coagulation and resultant fibrin formation. The conversion of the inert protein plasminogen to the active proteolytic enzyme plasmin by activator is considered to be the basic stage of this mechanism. Activator itself may be released from tissue directly or by conversion of an inert proactivator by lysokinase into an active enzymic form. When plasmin is released into the circulation it is normally bound and neutralized by antiplasmin and the actual process of fibrinolysis is thought to take place either because the plasmin antiplasmin complex dissociates as it comes in contact with fibrin (Ambrus, Back & Ambrus 1962), or because plasminogen, bound to fibrin, is converted in situ into active plasmin (Fletcher, Alkjaersig & Sherry 1962). Besides fibrin plasmin can also digest fibrinogen and other coagulation factors (VIII and V), and overactivity of the fibrinolytic mechanism is considered to lead to depletion of these factors and so promote abnormal bleeding. There is a growing opinion that conversely, the result of underactivity may be the excess formation of fibrin and an increased risk of thrombosis due to intravascular fibrin formation.