Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.4.21.68 (tissue plasminogen activator)
 11,311 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Intravenous administration of tissue plasminogen activator immediately after the injection of numerous small blood clots into the carotid circulation in rabbit embolic stroke model animals caused a significant reduction in neurological damage. In vitro studies indicate that tissue plasminogen activator produced substantial lysis of clots at concentrations comparable to those expected in vivo, suggesting that this may be the mechanism of action of this drug. Drug-induced hemorrhages were not demonstrable. Tissue plasminogen activator may be of value for the immediate treatment of embolic stroke.
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PMID:Tissue plasminogen activator reduces neurological damage after cerebral embolism. 393 54

Tissue plasminogen activator (tPA) was purified from serum-supplemented culture media in a single-step immunoaffinity chromatographic procedure. This was done by producing a monoclonal antibody to tissue plasminogen activator. The antibody is a murine IgG1, kappa light chain molecule. The antibody was coupled to CNBr-activated Sepharose 4B. Tissue plasminogen activator was isolated from serum supplemented tissue culture media by immunoaffinity chromatography using a relatively high ionic strength equilibration buffer and an acidic elution buffer.
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PMID:Immunoaffinity purification of tissue plasminogen activator from serum-supplemented conditioned media using monoclonal antibody. 393 81

Tissue plasminogen activator produced by a human melanoma cell line (Bowes), was purified from large volumes of supernatant fluid using immunosorbent chromatography on monoclonal antibodies, followed by chromatography on lysine-Sepharose 4B and gel filtration on Sephadex G-150. Immunosorbents based on monoclonal antibodies were shown to be preferable to those based on polyclonal antibodies for several reasons: efficient binding and desorption, high yield along with a high degree of purification. The overall recovery was about 50%. A homogeneous sample of single-chain tissue plasminogen activator with a molecular weight of approx. 65 000 was obtained as judged by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulphate. Amino acid sequence analysis revealed two N-terminals in equal yields, corresponding to the long and short tissue plasminogen activator structures previously reported by others. The pure preparations of tissue plasminogen activator showed specific activities of about 200 000 IU/mg protein.
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PMID:Large-scale purification of human tissue-type plasminogen activator using monoclonal antibodies. 404 Mar 96

The function of fibrinolysis is to dissolve fibrin clots. The agent of fibrinolysis is plasmin, a glycoprotein with gram molecular weight (GMW) of 90,000. Under natural conditions, plasminogen is converted to plasmin by tissue plasminogen activator (TPA). Activation occurs on the fibrin surface, thus confining proteolytic activity to the appropriate site. Tissue plasminogen activator, produced by monoclonal methods, has recently been made available for limited therapeutic use. Currently streptokinase and urokinase are widely used therapeutically to activate plasminogen. These agents cause plasmin to be formed which is free in the circulation as well as bound to fibrin, resulting in proteolysis of circulating plasminogen and clotting factors. Fibrinolytic therapy has proven to be more beneficial than anticoagulation alone for deep vein thrombi and for pulmonary emboli. During therapy, laboratory studies demonstrate reduced concentrations of plasminogen, fibrinogen, and of alpha-2 plasmin inhibitor, and prolongation of activated partial thromboplastin time and thrombin time. Laboratory findings must be correlated with the clinical course. Demonstration of circulating plasmin-antiplasmin complex may be a useful indicator of active fibrinolysis.
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PMID:Fibrinolysis--a review. 623 87

Tissue plasminogen activator (t-PA) in plasma was separated from inhibitors by adsorption on lysine-Sepharose. It was then determined indirectly by measuring the plasmin generated from plasminogen with poly-lysine as stimulator, in a chromogenic, parabolic rate assay. The reaction proceeded with tissue plasminogen activator and plasmin(ogen) adsorbed on the gel, and followed the kinetics described for similar parabolic rate assays in soluble systems. The assay was standardized against melanoma plasminogen activator (m-PA) and had the sensitivity range of 0.001-0.020 IU (4-80 pg). Anti-m-PA IgG quenched the activity generated in plasma on venous occlusion and part of the activity in pre-occlusion plasma. The method was sensitive to purified urokinase. The basic plasma values in resting normal individuals were: mean 0.08, range 0.01-0.26 X 10(3) IU/l (n = 19), and after 20 min of venous occlusion: mean 2.48, range 0.24-4.34 X 10(3) IU/l (n = 10). The assay correlates well with a fibrin plate method, r = 0.96.
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PMID:A sensitive assay for tissue plasminogen activator activity in plasma, using adsorption on lysine-sepharose. 654 74

The effect of thrombin on the release of tissue plasminogen activator from endothelial cells was studied in primary cultures of human umbilical vein endothelial cells. Tissue plasminogen activator concentration in conditioned medium was measured by a two-site radioimmunometric assay. The addition of increasing concentrations (0.01 to 10 U/ml) of thrombin to confluent cultures produced a saturable, dose-dependent increase in the rate of release of tissue plasminogen activator. A sixfold increase in tissue plasminogen activator concentration (from 2 to 12 ng/ml) occurred after the addition of 1 U/ml thrombin (8 X 10(-9) M) to cultures containing 5 X 10(4) cells/cm2. Enhanced release was not observed until 6 h after thrombin addition, reached a maximum rate of 1.3 ng/ml per h between 8 and 16 h, and then declined to 0.52 ng/ml per h after 16 h. The 6-h lag period before increased tPA release was reproducible and independent of thrombin concentration. Thrombin inactivated with diisopropylfluorophosphate or hirudin did not induce an increase in tissue plasminogen activator levels. A 50-fold excess of diisopropylfluorophosphate-treated thrombin, which inhibits binding of active thrombin to endothelial cell high affinity binding sites, did not inhibit the thrombin-induced increase. It is concluded that proteolitically active thrombin causes an increase in the rate of release of tissue plasminogen activator from cultured human endothelial cells. The 6-h interval between thrombin treatment and enhanced tissue plasminogen activator release may reflect a delaying mechanism that transiently protects hemostatic plugs from the sudden increase in the local concentration of this fibrinolytic enzyme.
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PMID:Thrombin stimulates tissue plasminogen activator release from cultured human endothelial cells. 654 70

The relative fibrinogenolytic, fibrinolytic and thrombolytic properties of human tissue plasminogen activator and human urokinase were compared in purified systems, in whole human plasma and in a system composed of a radioactive human blood clot (125I-fibrinogen) hanging in circulating human plasma. The human tissue plasminogen activator was highly purified from the culture fluid of a human melanoma cell line. In purified systems composed of fibrinogen of fibrin, plasminogen and alpha 2-antiplasmin as well as in whole plasma, tissue plasminogen activator digested fibrin without degrading fibrinogen significantly. Urokinase did not have this specific fibrinolytic effect. In the circulating plasma system, the degree of fibrinolysis was proportional to the amount of activator added, tissue plasminogen activator being about 10 times more efficient than urokinase. In addition, tissue plasminogen activator appeared to cause negligible fibrinogen degradation. Tissue plasminogen activator still induced significant thrombolysis at a concentration of 10 IU per ml whereas no effect of urokinase was observed at 20 IU per ml. Infusion of 100 IU (1 microgram) of tissue plasminogen activator per ml resulted in moderate activation of the fibrinolytic system as judged from a decrease of plasminogen and alpha 2-antiplasmin to 40-50 percent. Nevertheless, extensive fibrinolysis (50 to 80 percent of radioactivity released after 12 hrs) and only very limited fibrinogenolysis were observed. An equivalent amount of urokinase (100 IU per ml) only induced approximately 15 percent lysis in 12 hrs. At higher concentrations of urokinase (260 IU per ml or more) extensive activation of the fibrinolytic system was obtained as evidenced by a depletion of plasminogen, alpha 2-antiplasmin and fibrinogen. This was associated with extensive fibrinolysis (approximately 60 percent after 12 hrs). It is concluded that human tissue plasminogen activator is a more specific and effective fibrinolytic-thrombolytic agent than human urokinase.
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PMID:Comparison of the relative fibrinogenolytic, fibrinolytic and thrombolytic properties of tissue plasminogen activator and urokinase in vitro. 702 39

Thrombolytic therapy in acute myocardial infarction is of established value in recanalizing the occluded coronary artery, reducing infarct size, and decreasing mortality. Here, we review the extensive information provided by large clinical trials on agent and patient selection, timing of treatment, adjuvant therapies, and complications. Early treatment is of prime importance. Tissue plasminogen activator is slightly superior to streptokinase, especially in young patients treated early. Intravenous heparin should be used in conjunction with tissue plasminogen activator, although its role when streptokinase is used is less clear. Aspirin, beta-blockers, and converting enzyme inhibitors are of proven value as adjunctive therapies; nitrates and magnesium are not. Newer antithrombotic and antiplatelet agents (eg, hirudin and glycoprotein IIb/IIIa receptor antagonists) may further improve results.
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PMID:Thrombolysis in the era of the randomized trials. 754 79

Components of the coagulation and fibrinolytic cascades, prothrombin and activated partial thromboplastin times, endotoxin activity, and albumin concentration were measured in blood and peritoneal fluid from 20 healthy horses and from 153 horses with acute gastrointestinal tract diseases at admission. Overall, 77% (117/153) of affected horses survived to discharge from the hospital, and 85% (82/97) of horses discharged were reported to be normal 9 to 14 months later. Significant differences in hemostatic factors were more common in peritoneal fluid than in blood. Tissue plasminogen activator, plasminogen, protein C, antithrombin III, and alpha 2-antiplasmin activities and concentrations of fibrinogen and fibrin degradation products were significantly (P < 0.05) greater in peritoneal fluid from horses with colic, and, with the exception of fibrinogen concentration, were associated with detection of endotoxin. Higher values for these variables, except tissue plasminogen activator activity, were significantly (P < 0.05) associated with survival. Plasminogen, antithrombin III, and alpha 2-antiplasmin activities were significantly (P < 0.05) greater in peritoneal fluid from horses with inflammatory or strangulating lesions, compared with those in horses with simple colic. Plasminogen-activator inhibitor type 1 activity, fibrin degradation products concentration, and prothrombin time were significantly (P < 0.05) greater in the blood of horses with colic. Survival was inversely associated with significantly (P < 0.05) greater intravascular concentrations of fibrin degradation products and fibrinogen and prothrombin time. This study revealed marked contrasts between peritoneal and intravascular coagulation and fibrinolysis in horses with colic, indicating that inferences regarding the peritoneal environment, particularly with respect to fibrinolytic capacity, should not be made on the basis of factors measured in blood.
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PMID:Intravascular and peritoneal coagulation and fibrinolysis in horses with acute gastrointestinal tract diseases. 759 47

The thrombolytic activity of tissue plasminogen activator was evaluated in a rabbit model of thromboembolic stroke using both various concentrations (3, 5, and 10 mg/kg; 20% bolus with the remaining 80% given over 30 min.) and routes of administration (intravenous versus regional intra-arterial). An autologous tin-tagged clot was embolized to the brain via the carotid artery. Tissue plasminogen activator was then given at the doses and routes noted (n = 3 in all groups). Thrombolytic activity was followed by serial x-rays of the tin-laden clot over a four-hour period. The brains were then removed and subjected to gross inspection. Only the intravenous dose of 5 mg/kg tissue plasminogen activator produced greater than 50% clot lysis in all animals. Doses of t-PA higher (10 mg/kg) or lower (3 mg/kg) than this were less effective in producing thrombolysis, demonstrating greater than 50% clot lysis in only one animal of each group. We conclude that in this model of thromboembolic stroke the intravenous administration of tissue plasminogen activator is more effective than intra-arterial, and that the optimal dose is in the range of 5 mg/kg.
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PMID:Tissue plasminogen activator: comparison of dose and route of administration in a rabbit model of thromboembolic stroke. 790 9


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