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)

The effects of Ro 44-9883, a new specific antagonist of platelet glycoprotein IIb-IIIa receptor, on thrombus formation and reocclusion after thrombolysis induced by tissue-type plasminogen activator (t-PA) were compared with those of vapiprost, a thromboxane (TX) A2 receptor antagonist, using a photochemically-induced thrombosis model in the guinea-pig femoral artery. Pretreatment with Ro 44-9883 (5, 10 and 20 micrograms/kg/min, i.v.) prolonged the time required to occlude the artery in a dose-dependent manner. Ro 44-9883 at 10 and 20 micrograms/kg/min significantly inhibited ex vivo platelet aggregation in whole blood induced by collagen, ADP or U46619. Vapiprost 0.3 mg/kg inhibited thrombus formation and platelet aggregation induced by collagen or U46619, to the same extent as Ro 44-9883 at the higher doses. In the thrombolysis study, Ro 44-9883 at the higher doses given as comedication with t-PA reduced the time to achieve reperfusion and increased the vascular patency after successful reperfusion. Vapiprost also significantly reduced the time to reperfusion and prevented reocclusion. However, the vascular patency after thrombolysis by t-PA with vapiprost was significantly increased compared with Ro 44-9883. Ro 44-9883 inhibited platelet aggregation, but did not prevent TXA2 formation in platelets. Thus, vascular contraction mediated by platelet-derived TXA2 may be responsible for lower efficacy of Ro 44-9883 against reocclusion compared with vapiprost. These results indicate that not only platelet aggregation but also vasoconstriction may contribute to reocclusion after t-PA-induced thrombolysis in the guinea-pig.
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PMID:Comparison of antithrombotic effects of GPIIb-IIIa receptor antagonist and TXA2 receptor antagonist in the guinea-pig thrombosis model: possible role of TXA2 in reocclusion after thrombolysis. 749 79

Epidermal growth factor (EGF) or transforming growth factor-alpha (TGF-alpha) stimulated cell migration, chemotaxis, and the expression of tissue-type plasminogen activator (t-PA) in human omental microvascular endothelial (HOME) cells. Hepatocyte growth factor (HGF) stimulated cell proliferation, but had a negligible stimulatory effect on cell migration, the expression of t-PA and tube-like formation into collagen gel in HOME cells. Basic fibroblast growth factor stimulated cell proliferation, cell migration, tubulogenesis and the expression of urokinase-type plasminogen activator (u-PA) in bovine aortic endothelial (BAE) cells. HOME and BAE cells had both high- and low-affinity receptors for HGF. In BAE cells, u-PA activity and tube-like structures in collagen gel were induced in the presence of HGF alone. In contrast, in HOME cells, t-PA activity and tube-like structures were induced in the presence of TGF-alpha alone, but not in the presence of HGF alone. However, we observed a marked induction of tube formation by HOME cells when both t-PA and HGF were added simultaneously. In the model system for tumor angiogenesis, when HOME cells were co-cultured with a renal cancer cell line, KPK13, tube-like structures were induced in the presence of HGF:KPK13 cells expressed large amounts of t-PA mRNA. Our present study suggested that HGF in concert with active t-PA could be angiogenic in HOME cells.
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PMID:Cooperative roles of hepatocyte growth factor and plasminogen activator in tubular morphogenesis by human microvascular endothelial cells. 750 7

Cardiopulmonary bypass (CPB) induces a bleeding defect which leads to enhanced blood loss. A double-blind study was carried out comparing aprotinin with placebo in patients undergoing re-operation for heart valve replacement. The results confirm that aprotinin is effective at reducing such loss. In the placebo treated group, significant increases were observed, during CPB, in the plasma concentrations of fibrinolytic activity, tissue plasminogen activator antigen, D-dimer, and beta-thromboglobulin. Platelet counts fell within 5-10 min of the patients going onto CPB, but this could be accounted for by the dilutional effect of the extracorporeal circuit. Inhibition of responsiveness of platelets, as judged by aggregometry, was significant only at the end of bypass when collagen was the agonist and after protamine reversal when ristocetin was the agonist. CPB did not enhance the release, into the circulation, of glycocalicin (a proteolytic fragment of glycoprotein Ib). In the aprotinin-treated group, the formation of fibrin degradation products as measured by D-dimer was inhibited. However, aprotinin did not influence the change in platelet count, suppress beta-thromboglobulin release from platelets, prevent the inhibition of platelet function or influence the concentration of plasma glycocalicin during the study period. These observations confirm that CPB leads to a fibrinolytic state and less responsive platelets. This study also indicates that aprotinin-induced reduction in blood loss is associated with inhibition of plasmin-mediated fibrin digestion and that the mechanism by which aprotinin reduces blood loss is not via protection of platelets during CPB.
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PMID:Aprotinin reduces cardiopulmonary bypass-induced blood loss and inhibits fibrinolysis without influencing platelets. 751 Sep 90

The effects of different kinds of acute stress on collagen-induced whole blood platelet aggregation and fibrinolysis in relation to blood serotonergic measures were studied. In rats water-immersion restraint stress resulted in a shortening of euglobulin clot lysis time (ECLT), an increase in tissue plasminogen activator (tPA) activity with a concurrent fall in its inhibitor activity. Footshock caused rather a suppression in fibrinolysis with a prolongation of ECLT and a decline in tPA activity as well as a reduction in whole blood platelet aggregation induced by collagen. Serotonin (5-HT) level, a marker of a severity of stress, increased after footshock application with a concomitant rise in its major metabolite-5-hydroxyindoleacetic acid (5-HIAA). This indicates an enhanced 5-HT metabolism. Following water-immersion restraint stress 5-HT and 5-HIAA levels did not differ from controls. In both groups of stressed animals an inverse correlation between tPA activity and blood serotonin was observed. Our data indicate that these types of stress may influence either fibrinolysis or peripheral serotonergic mechanism in different ways. Acute and severe stress such as footshock by causing an impairment in fibrinolysis and a rise in 5-HT may contribute to the pathogenesis of thrombosis and henceforth to the development of atherosclerosis.
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PMID:Stress-dependent changes in fibrinolysis, serotonin and platelet aggregation in rats. 751 40

To clarify the activity states of coagulation and fibrinolysis in patients with a permanent pacemaker, we studied 29 patients more than 4 months after operation. They were divided into a single pacemaker lead group (S, n = 14) and a double lead group (D, n = 15). Prothrombin time, activated partial thromboplastin time, fibrinogen, antithrombin III, tissue-type plasminogen activator (tPA) activity, plasminogen activator inhibitor type-1 (PAI-1) activity, and platelet aggregation were measured and compared to those in an age-matched control group (C, n = 7). The effects of low dose aspirin (81 mg/day) in the patients (n = 21) were also studied 2 weeks after administration. PAI-1 activity in groups S and D was significantly higher than that in the group C (53.5 +/- 36.5, 86.8 +/- 59.2 ng/mL vs 19.4 +/- 7.2 ng/mL; P < 0.01 and P < 0.005). Platelet aggregation induced by collagen was slightly higher in groups S and D than group C. Other parameters were not significantly different. In the patients, low dose aspirin significantly suppressed collagen induced platelet aggregation (71.8 +/- 20.3% vs 41.7 +/- 28.3%; P < 0.005), but not PAI-1 activity. tPA activity was increased significantly by the low dose aspirin administration (3.94 +/- 1.85 ng/mL vs 2.48 +/- 1.19 ng/mL; P < 0.005). Thus, PAI-1 activity in patients with a permanent pacemaker is elevated, and the activity is not suppressed by low dose aspirin unlike the platelet aggregation.
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PMID:Effect of low dose aspirin on augmented plasminogen activator inhibitor type 1 activity in patients with permanent pacemakers. 751 98

The present recommendation is that aprotinin should be started before cardiac surgery, but as bleeding is only a problem in a minority, most patients are treated unnecessarily. In a prospective, randomised, double-blind trial we have studied the use of aprotinin, given only to the minority of patients who bled significantly post-operatively and who had not received prophylactic aprotinin. Sixty patients, who bled in excess of 400 ml in the first 3 h post-operatively were randomised to receive either aprotinin (2 x 10(6) KIU loading dose followed by an infusion of 0.5 x 10(6) KIU/h for 4 h) or placebo, in addition to conventional treatment. The demographic characteristics and the surgical procedures performed were similar in the two groups. Haematological variables were measured (A) before and (B) at the end of the infusion. Three patients were re-explored for excessive bleeding in each group and one patient died in each group. The patients in the aprotinin group bled significantly less and had higher haemoglobin levels on discharge than the patients in the placebo group. The tissue plasminogen activator antigen decreased and the fibrinogen level increased in the aprotinin group. In addition, aprotinin increased the number of surface GPIb platelet receptors as estimated by flow cytometry (36% versus 5%, P < 0.01) and maintained the platelet von Willebrand Factor activity (vWF). There was no significant difference in D-dimers, fibrin(ogen) degradation products, plasma vWF activity and antigen, platelet vWF antigen, platelet aggregation (to collagen, arachidonic acid, platelet activating factor and ristocetin), platelet count or transfusion of blood products between the two groups.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Aprotinin inhibits fibrinolysis, improves platelet adhesion and reduces blood loss. Results of a double-blind randomized clinical trial. 752 18

The effects of water immersion restraint stress on collagen-induced platelet aggregation in whole blood, and on the fibrinolytic and serotonergic systems in rats have been studied. One hour long stress caused a release of tissue plasminogen activator (tPA) into the blood and a shortening of euglobulin clot lysis time (ECLT), whereas restraint of longer duration was responsible for a reduction in platelet aggregation, an elevation in the activity of plasminogen activator inhibitor with a concomitant fall in tPA and a prolongation of ECLT relative to controls. Whole-blood and plasma serotonin and its metabolite 5-hydroxyindoleacetic acid were also higher in the stressed rats and whole-blood serotonin level showed a negative correlation with tPA in the stressed rats. Either stress and/or its duration are responsible for changes in both fibrinolytic and serotonergic systems.
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PMID:Time-dependent changes in platelet aggregation, fibrinolytic activity, and peripheral serotonergic measures in rats subjected to water immersion restraint stress. 752 68

Various radiographic contrast agents have anticoagulant or prothrombotic properties. Ionic agents are reported to have greater antithrombotic potential while nonionic agents are considered more thrombogenic. Some agents after fibrin structure and bind to platelets in purified systems. This study compared the effects of iohexol, a nonionic agent, and iothalamate, an ionic agent, on fibrin assembly, clot structure, platelet function and clot dissolution in plasma. Plasma gels containing increasing concentrations of iothalamate were composed of thinner fibers with decreased fiber mass/length ratios (mu) and reduced gel turbidity. Such clots were more rigid and more resistant to fibrinolysis induced by tissue plasminogen activator (tPA). Gel elastic modula increased from 10,000 to 27,000 dyn/cm2 as iothalamate concentration increased from 0 to 20 mM. 50% lysis time increased from 800 to 1,250 s with the addition of 10 mM iothalamate. At 20 mM, iothalamate had no effect on ADP-induced platelet aggregation but prolonged the lag phase seen with collagen-induced aggregation. Platelet force development increased from 15,300 to 20,400 dyn with 20 mM iothalamate. The effect of iohexol were similar. Gel optical density dropped from 0.50 to 0.32, mu fell from 3.3 to 2.2 x 10(13) D/cm, and elastic modulus rose from 11,000 to 24,000 dyn/cm2 as iohexol concentration was increased from 0 to 20 mM. Clots formed in the presence of 60 mM iohexol and tPA did not dissolve in 72 h while control clot 50% lysis time was 450 s. At concentrations > or = 40 mM, iohexol completely blocked collagen-induced platelet aggregation. Platelet force development increased from 7,660 to 19,600 with 40 mM iohexol. Contrast media possess profound fibrin-altering activities in plasma. Fibrin formed in the presence of some agents may be significantly more resistant to fibrinolysis.
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PMID:Effects of ionic and nonionic contrast media on clot structure, platelet function and thrombolysis mediated by tissue plasminogen activator in plasma clots. 755 56

High ambient glucose concentration, linked to vascular complications in diabetes in vivo, modulates mRNA expression of fibronectin, collagen, tissue-type plasminogen activator, and plasminogen activator inhibitor and induces delayed replication and excess cell death in cultured vascular endothelial cells. To determine the role of high ambient glucose (30 mmol/l) in apoptosis, paired cultures of individual isolates of human umbilical vein endothelial cells (HUVECs) were exposed to both high (30 mmol/l) and low (5 mmol/l) concentrations of glucose for short-term (24, 48, and 72 h) and long-term (13 +/- 1 days) experiments. Incubation of HUVECs with high glucose for > 48 h increased DNA fragmentation (13.7 +/- 6.5% of total DNA, mean +/- SD) versus cultures kept in 5 mmol/l glucose (10.9 +/- 5.6%, P < 0.005), as measured by [3H]thymidine assays. Data were confirmed by apoptosis-specific fluorescence-activated cell sorter analysis of confluent HUVEC cultures, which displayed after long-term exposure to 30 mmol/l glucose a 1.5-fold higher prevalence of apoptosis than control cultures exposed to 5 mmol/l glucose (P < 0.005). In contrast, no increase in DNA fragmentation in response to 30 mmol/l glucose was seen for standardized cell lines (K 562, P 815, YT) and fibroblasts. Expression of clusterin mRNA, originally reported to be a molecular marker of apoptosis, was only slightly affected by short-term (24-h) high-glucose exposure but was significantly reduced after long-term incubation in 30 mmol/l glucose (82.2 +/- 13.8% of control) versus 5 mmol/l glucose, which questions the role of clusterin gene expression as a marker of apoptosis.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:High-glucose--triggered apoptosis in cultured endothelial cells. 758 31

To determine the effects of extracellular matrices on the function and morphology of hepatic sinusoidal endothelial cells, isolated rat hepatic sinusoidal endothelial cells were cultured in three-dimensional fashion on collagen gel containing various extracellular matrix components. Cells cultured on type I collagen gel with or without type IV collagen formed a cobblestone appearance on the surface of the gel. Cells cultured on laminin-containing type I collagen gel invaded the gel and exhibited three-dimensional tube formation with a decreased number of characteristic endothelial pores. Morphometrically, there was a significant relationship between the length of the tube formed and the concentration of laminin in the type I collagen gel. Cells cultured on Matrigel, which contains high concentrations of laminin, type IV collagen, fibroblast growth factor, tissue plasminogen activator, and other growth factors, formed a great number of tubes into a network on the surface of the gel, as is observed in the situ hepatic sinusoidal endothelial cells. Ultrastructurally, tube-forming endothelial cells cultured on Matrigel had many endothelial pores on the cell surface, with tubes (approximately 10 microns in diameter) formed by two or three hepatic sinusoidal endothelial cells. These results indicated that extracellular matrix components, especially laminin, induced the formation of tubes in cultured rat hepatic sinusoidal endothelial cells. Tube-forming sinusoidal endothelial cells cultured on Matrigel could provide more advantages than the two-dimensional culture model for investigating the function and morphology of these cells in vitro.
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PMID:Effects of extracellular matrices on tube formation of cultured rat hepatic sinusoidal endothelial cells. 765 5


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