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)

In this study the authors attempted to restore the coagulative fibrinolytic homeostasis that is compromised in peripheral vascular disease. Eleven patients with arterial disease, eleven with venous disease and seven healthy volunteers underwent oral treatment using 3 g of propionyl-L-carnitine divided into thrice daily doses for a period of 20 days. (1 g t.i.d.). This quaternaria amine is able to correct tissue hypoxia by increasing ATP and energy production and has the capacity to prevent alterations in endothelial membrane permeability. The authors observed a significant increase of t-PA synthesis on the 10th day of therapy in the arterial disease and control groups. All three groups showed a significant increase in t-PA synthesis on the 20th day of therapy. A significant decrease in PAI-1 activity was observed on the 10th and on the 20th day of therapy in both the patient groups, but not in the control group. Although the exact pathological mechanisms of peripheral vascular disease are complex and in many aspects still unknown, it is now absolutely certain that there is a pathogenetic role of functional imbalances. An important part is played by the reduction in t-PA synthesis and the increase in PAI-1 activity, and the authors conclude that it is necessary to use pharmaceutical substances to restore proper equilibrium.
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PMID:The action of propionyl-L-carnitine on the vasal endothelium: increased t-PA synthesis and a decrease in the activity of PAI-1. A preliminary study. 129 17

Binding of iodine-125-labeled thrombin to fibrin clots from two siblings with juvenile stroke was 30% of normal, and abnormally high amounts of the radioligand (not adsorbed by fibrin) were found in the supernatant. In concordance with this finding, supernatants from the patients' fibrin clots caused abnormal enhancement of platelet aggregation, ATP secretion, and binding of 125I-fibrinogen to platelets exposed to subthreshold concentrations of ADP or epinephrine. Hirudin suppressed the enhancing effect of the patients' supernatants, and substitution of gamma-thrombin for alpha-thrombin led to normalization of platelet responses. Under some experimental conditions, degradation of the patients' fibrinogen by plasmin was impaired. However, the euglobulin lysis time, the rate of fibrin degradation by plasmin, and the lysis of the patients' plasma clots by human melanoma tissue-type plasminogen activator were normal. Patients' plasmas, as well as purified fibrinogen, showed a prolonged thrombin time (partially corrected by 10 mM CaCl2) and an impaired release of fibrinopeptide A in response to thrombin. However, the release in response to reptilase was normal, and the reptilase, ancrod, and thrombin coagulase times were within control (normal) values. In addition, the patients' fibrinogen showed normal polymerization of preformed fibrin monomers, normal sialic acid content, and normal binding to ADP or epinephrine-stimulated platelets. Our studies support the concept that thrombin and platelets play an important role in the occurrence of stroke in these patients and suggest a direction to be followed to identify the mechanism(s) contributing to thrombosis in subjects with abnormal fibrinopeptide release.
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PMID:A role for platelets and thrombin in the juvenile stroke of two siblings with defective thrombin-adsorbing capacity of fibrin(ogen). 182 31

The uptake and internalization of tissue-type plasminogen activator (t-PA) by freshly isolated rat hepatocytes was investigated. Electron microscopic examination of the uptake of t-PA-colloidal gold conjugates (t-PA-gold) by isolated rat hepatocytes showed that t-PA-gold was internalized via coated pits. This was inhibited with excess t-PA. Uptake of 125I-t-PA by isolated rat hepatocytes was a rapid, saturable, and specific process. The initial rate of specific uptake was 0.1 fmol/10(6) cells per min. The specific uptake plateaued at 1.4 fmol/10(6) cells by 30 min and declined to 0.8 fmol/10(6) cells at 2 h. Depletion of cellular ATP by 85-90% did not affect the initial rate of specific uptake. However, specific uptake by ATP-depleted hepatocytes at 30 min was reduced by 37%. By 2 h specific uptake by ATP-depleted hepatocytes was only 5% lower than by untreated hepatocytes, suggesting that processing of t-PA and/or its receptor is ATP-dependent. Uptake of 125I-t-PA was temperature dependent. Specific uptake was reduced by approximately 20% at 22 degrees C and by 70% at temperatures below 16 degrees C. Finally, inhibition of coated pit formation by K(+)-depletion with nigericin decreased the uptake of 125I-t-PA. This inhibition was shown to be K(+)-specific since treatment with nigericin in the presence of K+ did not inhibit coated pit formation or 125I-t-PA uptake. A threshold K(+)-depletion level for inhibition of coated pit formation was also demonstrated since treatment under conditions that reduced cellular K+ by only 54% had no effect on coated pit formation or 125I-t-PA uptake. These data support our hypothesis that internalization of t-PA by isolated rat hepatocytes is via coated pits and suggest that uptake of t-PA is a receptor-mediated process.
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PMID:Internalization of recombinant tissue-type plasminogen activator by isolated rat hepatocytes is via coated pits. 197 6

Secretory proteins expressed in Chinese hamster ovary (CHO) cells interact to various degrees with glucose-regulated protein 78 (GRP78), a resident protein of the endoplasmic reticulum. von Willebrand factor (vWF) and wild-type tissue plasminogen activator (tPA) are efficiently secreted and exhibit a slight transient association with GRP78. Factor VIII and unglycosylated tPA are inefficiently secreted and display a more stable association with GRP78. We have studied the effect of ATP depletion mediated by carbonyl cyanide 3-chlorophenylhydrazone (CCCP) treatment on GRP78 association and secretion of factor VIII and vWF that are coexpressed in CHO cells. Low concentrations of CCCP in the medium prevented disassociation of factor VIII from GRP78 and blocked its secretion. In the same cells, higher concentrations of CCCP were required to block secretion of vWF. Thus, the block to factor VIII secretion at low CCCP concentrations did not result from a general defect in secretion. Secretion of unglycosylated tPA but not wild-type tPA from CHO cells was also blocked by low concentrations of CCCP. The increased sensitivity to CCCP concentration observed for secretion of factor VIII and unglycosylated tPA compared to wild-type tPA and vWF correlates with their degree of interaction with GRP78. In vivo, dissociation from GRP78 may be a primary ATP-dependent step in transport from the endoplasmic reticulum. ATP requirements for secretion of various proteins may vary.
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PMID:Protein dissociation from GRP78 and secretion are blocked by depletion of cellular ATP levels. 212 Jun 99

Defibrotide (D) is a natural polydeoxyribonucleotide from mammalian lungs with profibrinolytic and antithrombotic activities. D also has PGI2-stimulating and tissue plasminogen activator (TPA)-releasing activities, but has no anticoagulant properties. The protective effects of D were demonstrated very recently in a model for non-lethal ischemia in the cat. In the experiments reported here Defibrotide was tested in a model for acute myocardial ischemia leading to ventricular fibrillation (VF) and death of the cat. Occlusion of the coronary artery (LAD) at its origin induced VF and death in 17 of 20 control cats. When cats were treated with D (32 mg Kg-1, bolus i.v., + 32 mg Kg-1 h-1, i.v., after LAD occlusion) 19 of 20 animals survived until the end of experiments. D also prevented changes in plasma and myocardial CPK, hemodynamics and ECG. D was compared with a variety of pharmacological agents which are used clinically for specific cardiovascular diseases. The ability of D to promote considerable generation of PGI2 from vascular walls plus its ability to prevent the decreases in CPK-activity and ATP in the myocardial tissue may have roles in its beneficial effects against ischemic heart in the cat. However, the mechanism/s of the substantial protective effect of D against cardiac death has still to be clarified.
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PMID:Protective activity of defibrotide against lethal acute myocardial ischemia in the cat. 308 10

A maximum cell density of 8 x 10(6) viable human fibroblast cells/ml was obtained on microcarriers at a perfusion rate of 0.6 mL/min-a rate which maintained a quasi-steady state. The maximum tPA production was approximately 1.2 micrograms/ml and obtained when the cell density was relatively constant during the later periods of cultivation. Specific UTP and tPA production rates had a correlation factor of 0.85, and cell growth to oxygen consumption had an 0.92 correlation factor. ATP generation was strongly correlated to glutamine consumption, with a lower correlation to oxygen utilization.
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PMID:Kinetic analysis of cellular nucleotides correlated to growth and tPA production in perfusion cultures of human fibroblast cells. 776 89

The experiments reported here were carried out to define in greater detail actin's stimulation of plasmin generation by t-PA. Actin did not alter t-PA's hydrolysis of a synthetic substrate, and thus is unlikely to have a direct effect upon t-PA's proteolytic activity. When studied in a single-stage assay, actin accelerated t-PA-mediated plasmin generation from both Glu-plasminogen and Lys-plasminogen, indicating the central role of ternary complex formation. Although actin does not appear to bind two-chain urokinase (tcu-PA), it stimulates tcu-PA's cleavage of Glu-plasminogen. This finding suggests that actin alters the conformation of Glu-plasminogen to an open form. The failure of actin to increased plasmin generation by tcu-PA acting on Lys-plasminogen, which is in an open configuration, is consistent with this interpretation. Immunoglobin G, which shares with actin the property of binding to Glu-plasminogen after nicking by plasmin, did not stimulate tcu-PA's cleavage of Glu-plasminogen, indicating the uniqueness of actin's effects and suggesting interactions between actin and plasminogen at multiple binding sites. Unlike fibrin and heparin, whose stimulation of t-PA is related to polymer length actin is able to stimulate t-PA when presented in either a monomeric or polymeric form. Denaturation of actin by exposure to urea and guanidine increased its ability to stimulate plasmin generation by t-PA. Because actin's structure is maintained by a noncovalently bound adenine nucleotide (ATP or ADP), exposure to ATP/ADPases found in plasma and on cell membranes might also result in its denaturation. Actin treated with an enzyme functionally similar to such ecto-ATP/ADPases, potato apyrase, was more potent than native actin in stimulating plasmin generation by t-PA. The effects of apyrase were blocked by the addition of the plasma actin-binding proteins, gelsolin and the vitamin D-binding protein (DBP). Thus, denaturation of actin may occur in under physiologic conditions, with potential biological consequences. Actin thus appears to be unique with regard to its interactions with the fibrinolytic system and plasma actin-binding proteins may serve to protect the host from the effects of denatured actin.
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PMID:Actin stimulates plasmin generation by tissue and urokinase-type plasminogen activators. 823 51

Endothelial cells (EC) are important regulatory cells in physiology and pathology. in vitro studies with rat EC from heart tissue are hampered by laborious isolation and purification procedures, low yield, and limited lifespan of the cells. Therefore, it is essential to obtain long-term heart EC lines that offer a more adequate in vitro system for studying rat heart EC. An ex vivo perfusion model was used to isolate EC from rat heart. Isolation and culture conditions were modified to allow spontaneous development of immortalized rat heart EC (RHEC) lines. Produced cell lines were tested for endothelial nature using a panel of markers. The selected RHEC lines were subsequently tested for a series of phenotypic and functional properties representative of EC in the context of physiologic and inflammatory functions in vivo. A series of three spontaneous RHEC lines was produced from 13 isolations from Lewis rat hearts: RHEC-3, RHEC-10, and RHEC-11. These lines were stable for more than 30 passages (RHEC-3 for more than 100). The cell lines were tumorigenic and developed hemangiomas on in vivo injection. All three lines expressed major histocompatibility complex (MHC) class I but no MHC class II. Intercellular adhesion molecule 1 was only expressed by RHEC-3. Cytokine stimulation induced vascular cell adhesion molecule 1 in RHEC-3 and RHEC-11 as well as MHC class II in all three lines in different quantities. The phenotypic characteristics of the different RHEC lines resembled the myocardial microvascular endothelium in situ. The three lines expressed angiotensin-converting enzyme, and they responded to histamine and ATP but not to thrombin and bradykinin. They constitutively produced small amounts of endothelin and high levels of tissue plasminogen activator; they produced little (after stimulation with phorbol-ester PMA) or no von Willebrand factor. The RHEC lines produced thromboxane A2 but no prostacyclin; on stimulation with arachidonic acid and A23187, they produced prostaglandin E2. Therefore, we conclude the following. 1) The described isolation and culture technique is successful for production of spontaneous stable EC lines from rat heart. 2) RHEC-3, -10, and -11 can be considered a series of different lines representative of the heterogeneity of heart microvascular endothelium in vivo. 3) The RHEC lines offer a series of valuable tools to study various heart EC functions and mechanisms in physiology and pathology.
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PMID:Production and characterization of spontaneous rat heart endothelial cell lines. 878 Jan 62

The aim of this study is to evaluate the effects of whole blood filtration after a storage time of 20-24 hours at laboratory temperature using the in line filter Leucoflex LST1. The study concerns 49 blood donations in which we studied leukocyte depletion, proteins (IgG, IgA, IgM, haptoglobin, C3, C4), coagulation factors (fibrinogen, factors XII, XI, IX, VIII, V, proteins S and C, plasminogen, tPA, D-Dimers, PDF) at day 1, the parameters of conservation (ATP, 2-3 DPG, extra cellular potassium, haemolysis, pH) of red blood cell concentrates (RCCs) and bacteriological sterility at day 1 and 42. Despite a correct leukocyte depletion (mean depletion of 3.96 log), a 10 fold higher mean level of residual leukocytes/unit than with buffy coat poor RCC filtration (0.514.10(6) vs 0.051.10(6)) is observed. Moreover a lot of concentrates are not in accordance with French regulations (7/42 with more than 1.10(6) leukocytes/unit). The variation of the rates of IgG, IgA, IgM, haptoglobin, C4 and protein C is not significant. For the others there is a slight decrease with a mean level remaining in a physiological range. No sign of activation is noted. The sterility assays remain negative and the RCC conservation is not altered. In conclusion, even if the quality of the leukocyte depletion is not satisfactory in our study and has to be stated more precisely by multicenter studies, the whole blood filtration does not alter the quality of the derived components and allows us obtain RCC in a bigger volume and containing more haemoglobin than with the classical procedure after removing the buffy-coat [10].
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PMID:[Consequences for labile blood products of leukocyte depletion by whole blood filtration using the Leucoflex LST1 in-line filter. Evaluation of the Leucoflex LST1 filter]. 952 20

Nowadays besides the commonly accepted atherogenic risk factors a special emphasis is laid on the significance of testosterone in atherogenesis in men which physiologic deficit during "andropause" is able to promote this pathology. An elevated estradiol:testosterone ratio seems to be an independent risk factor of atheromatous heart complications. There is a proved positive correlation between free testosterone, total testosterone, dihydrotestosterone and HDL-cholesterol, apoA1 apolipoprotein. The relationship between LDL-cholesterol, VLDL-cholesterol, total cholesterol and total and free testosterone seems to be unanimous, but in certain studies the beneficial influence of testosterone on the mentioned lipids has been observed. The discussed hormone is also functionally connected with coagulation and fibrynolisis; a positive correlation was found between endogenous testosterone and tPA-Fx and a negative correlation between testosterone and PAI-1, fibrinogen, D-dimers, alpha 2-antiplasmin. Testosterone is a functional regulator of the vascular tonus and influences on reological properties of microcirculation (the application of testosterone infusion into canine coronary arteries causes the dilatation of main and the small vessels, through NO syntetase induction and ATP-dependent K(+)- channel activation). A statistically significant positive correlation between testosterone and insulin has been stated (an elevated oestradiol:testosterone ratio is connected with the insulin resistance). Additionally a negative relationship between testosterone and android obesity has been observed. Although nowadays there are more and more facts proving the benefits of the retaining the proper testosterone levels in aging men, the final influence of the testosterone supplementary therapy on atherogenesis is not solved.
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PMID:[Testosterone and atherosclerosis in males during andropause]. 1039 Oct 62


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