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)

Primary fetal human adrenocortical cells of definitive zone origin were transfected by electroporation with pSV3neo, a plasmid coding for SV40 T antigen and neo, which confers resistance to the antibiotic G418. The clones obtained proliferated for 30 to 40 population doublings after isolation when grown under standard medium conditions, and then entered 'crisis'. When early-passage clones were incubated with cyclic AMP (1:1 N6-monobutyryl and 8-bromo analogues), cell rounding was observed, as in primary cultures of human adrenocortical cells. As previously shown in bovine adrenocortical cells, rounding was inhibited with a monoclonal antibody against urokinase plasminogen activator but not with a monoclonal antibody against tissue plasminogen activator. The regulation of the steroidogenic pathway in clones was investigated. The effects of cyclic AMP and activation of protein kinase C were examined in cells maintained in defined medium or in the presence of serum. 17 alpha-Hydroxylase was strongly induced by cyclic AMP, as evidenced by Northern blotting and by the conversion of progesterone or 25-hydroxy-[1,2-3H]cholesterol, this induction being blocked by low concentrations of 12-O-tetradecanoylphorbol-13-acetate (TPA). Cholesterol side-chain cleavage enzyme was strongly induced by cyclic AMP, and clones also showed low activities of 21-hydroxylase and 11 beta-hydroxylase. Under all circumstances levels of 3 beta-hydroxysteroid dehydrogenase (3 beta-HSD), as assessed by Northern blotting or by conversion of 25-hydroxycholesterol, were very low. 3 beta-HSD was not induced by cyclic AMP or TPA alone, but was induced by the combination of the two agents. The regulation of 17 alpha-hydroxylase and 3 beta-HSD resembles that previously described in primary cultures of human fetal adrenocortical cells. Thus, transfection with SV40 T antigen resulted in the production of clones which preserve the unique characteristics of the human adrenal cortex.
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PMID:Expression of 17 alpha-hydroxylase and 3 beta-hydroxysteroid dehydrogenase in fetal human adrenocortical cells transfected with SV40 T antigen. 132 52

The concentrations of tissue plasminogen activator (t-PA), urokinase plasminogen activator (u-PA) and plasminogen activator inhibitor (PAI-1) have been determined in endometrial curettings obtained from 46 subfertile women during proliferative, early or late secretory phases of the menstrual cycle. t-PA activity and antigen concentrations was significantly higher (P < 0.001) in late secretory endometrium than in proliferative or early secretory endometrium. Higher concentrations of PAI-1 antigen (P < 0.05) were also noted in late secretory phase than in proliferative and early secretory endometrium. However, u-PA concentration was not significantly different and no PAI activity could be demonstrated in the menstrual phases studied. Zymography studies confirmed the presence of both t-PA and u-PA in the endometrium. Ovarian hormonal patterns may therefore influence the activity of plasminogen activators especially of t-PA in the endometrium during various phases of the menstrual cycle.
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PMID:Concentration of plasminogen activators and inhibitor in the human endometrium at different phases of the menstrual cycle. 133 23

Smooth muscle cells (SMCs) in balloon-injured rat carotid artery express tissue-type plasminogen activator (t-PA) at a time when they are migrating from the media to the intima. Since heparin inhibits SMC migration and intimal thickening, we have examined the possibility that heparin might also inhibit t-PA expression. Heparin (nonanticoagulant fraction; molecular weight, approximately 6,000) was administered by continuous intravenous infusion (1.0 mg/kg per hour) to Sprague-Dawley rats subjected to balloon injury of the left common carotid artery. At various times up to 14 days after injury, plasminogen activator expression was analyzed by zymography, plasmin generation, enzyme-linked immunosorbent assay, Northern blotting, and in situ hybridization. This dose of heparin inhibited SMC accumulation at 14 days by 60%. Both urokinase plasminogen activator (u-PA) and t-PA activity increased in injured arteries and reached a maximum at 7 days. Heparin treatment decreased t-PA, but not u-PA, activity. Total t-PA protein was decreased by treatment with heparin but not chondroitin sulfate, and the decrease in t-PA protein was associated with decreased t-PA mRNA in the media. These results in the injured rat carotid artery agree with our earlier observations that heparin inhibits t-PA gene expression in cultured baboon aortic SMCs. They also provide support for the hypothesis that heparin interferes with the expression of certain proteases required for SMC migration and proliferation.
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PMID:Heparin inhibits the expression of tissue-type plasminogen activator by smooth muscle cells in injured rat carotid artery. 137 98

Regulation of the activity of proteolytic enzymes is of major importance in the turnover of connective tissues. The search for physiologically relevant activation mechanisms of principal tissue-degrading enzymes, e.g., metalloproteinases, has therefore been of wide interest. We have now studied whether the initiating factor of the fibrinolytic system, urokinase plasminogen activator (u-PA), may also function in the early steps of activation of one of the metalloproteinases, the M(r) 72,000 gelatinase/type IV collagenase produced by cultured fibroblasts. Treatment of the secreted M(r) 72,000 proteinase by u-PA yielded a cleavage product of M(r) 62,000 as revealed by fluorography of radioactively labeled proteins as well as by gelatin zymography SDS-PAGE gels. The u-PA-catalyzed cleavage of the M(r) 72,000 proteinase was blocked by anti-u-PA antibodies, but was unaffected by the plasmin inhibitor aprotinin, thus indicating a specific action for the activator. On the contrary, the tissue activator of plasminogen, t-PA, did not cleave the type IV collagenase in similar assays. u-PA-catalyzed cleavage of recombinant type IV collagenase, produced in a baculovirus expression system, yielded a similar M(r) 62,000 activity in gelatinolysis assay. Zymograms of the isolated pericellular matrices of cultured fibroblasts also revealed M(r) 72,000 gelatinolytic polypeptide that was converted to an M(r) 62,000 form by u-PA. Both polypeptides were recognized in immunoblotting by antibodies against the gelatinase/type IV collagenase, suggesting immunological identity with the secreted enzyme. Thus the M(r) 72,000 gelatinase/type IV collagenase is not only secreted, but also deposited into the pericellular fibroblast matrix, and both forms are substrates for u-PA. The results suggest a new potential role for u-PA as a direct regulator of metalloproteinase-mediated extracellular proteolysis via the cleavage of the M(r) 72,000 gelatinase/type IV collagenase to an M(r) 62,000 form.
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PMID:Proteolytic processing of the 72,000-Da type IV collagenase by urokinase plasminogen activator. 139 99

Thrombospondin is a multifunctional glycoprotein of platelet alpha-granules and a variety of growing cells. We demonstrate that thrombospondin is a slow tight-binding inhibitor of plasmin as determined by loss of amidolytic activity, loss of ability to cleave fibrinogen, and decreased lysis zones in fibrin plate assays. Stoichiometric titrations indicate that approximately 1 mol of plasmin interacts with 1 mol of thrombospondin, an unexpected result considering the trimeric nature of thrombospondin. Plasmin in a complex with streptokinase or bound to epsilon-aminocaproic acid is protected from inhibition by thrombospondin, thereby implicating the lysine-binding kringle domains of plasmin in the inhibition process. Thrombospondin also inhibits urokinase plasminogen activator, but more slowly than plasmin, stimulates the amidolytic activity of tissue plasminogen activator, and has no effect on the amidolytic activity of alpha-thrombin or factor Xa. These results, therefore, identify thrombospondin as a new type of serine proteinase inhibitor and potentially important regulator of fibrinolysis.
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PMID:Thrombospondin is a slow tight-binding inhibitor of plasmin. 153 Oct 22

The effect of therapeutic and pharmacological concentrations of tiaprofenic acid, a non-steroidal anti-inflammatory drug (NSAID), on the synthesis of the plasminogen activators, urokinase plasminogen activator (uPA) and tissue plasminogen activator (tPA), and the plasminogen activator inhibitors 1 and 2 (PAI-1 and PAI-2), by human synovial membranes isolated from osteoarthritis (OA) and rheumatoid arthritis (RA) sufferers was evaluated. Both forms of plasminogen activator (PA) and PA inhibitor (PAI) were synthesized by the arthritic synovium. PAI-1 and PAI-2 were both synthesized in greater amounts than the plasminogen activators. Tiaprofenic acid induced a dose-dependent decrease in uPA synthesis in both OA and RA, particularly in OA synovium, but had no true effect on tPA. Tiaprofenic acid also exerted a suppressive effect on the synthesis of PAI-1 in both OA and RA synovial membranes, and on the release of PAI-2 in RA synovium. The results of this study indicate that a decrease in uPA synthesis may be one of the mechanisms by which tiaprofenic acid could exert its effects on the arthritic process. The suppressive action of tiaprofenic acid on PAI is not likely to have a significant impact on the balance of plasminogen activators and plasminogen activator inhibitors, as plasminogen activator inhibitors are synthesized in greater amounts than plasminogen activators.
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PMID:Effects of tiaprofenic acid on plasminogen activators and inhibitors in human OA and RA synovium. 155 50

Thrombolytic therapy frequently induces a "lytic state" associated with a decrease in plasma plasminogen concentration that could limit therapeutic efficacy. We therefore investigated the influence of soluble plasminogen concentration on in vitro lysis of retracted whole-blood clots in plasma from normal subjects and from patients undergoing thrombolytic therapy. With recombinant tissue plasminogen activator (1000 ng/ml) or two-chain urokinase plasminogen activator (250 U/ml), minimal clot lysis occurred in normal plasma depleted of plasminogen by lysine Sepharose chromatography. Clot lysis induced by two-chain urokinase plasminogen activator increased progressively in normal plasma at initial plasminogen concentrations between 0.06 to 6 U/ml, whereas maximum lysis with recombinant tissue plasminogen activator occurred between 0.5 U/ml and 1 U/ml and was less at lower and higher concentrations of plasminogen. Incubation of whole-blood clots in normal plasma with recombinant tissue plasminogen activator resulted in little change in plasminogen concentration during 6 hours, with a constant rate of clot lysis. Incubation with two-chain urokinase plasminogen activator, however, caused a rapid decrease in plasminogen concentration and a corresponding decrease in lysis rate; lysis rate was restored after repletion with purified plasminogen. The effect of in vivo activator-induced plasminogen depletion on in vitro clot lysis rates was tested with plasma obtained from patients 90 to 120 minutes after they had received 30 mg of acylated plasminogen-streptokinase activator complex that showed depletion of plasminogen to 14% +/- 2%. These plasma samples produced only 4% +/- 1% in vitro clot lysis during 4 hours but lysis increased progressively after repletion with 1, 2, and 4 U/ml plasminogen.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Depletion of plasminogen in vitro or during thrombolytic therapy limits fibrinolytic potential. 161 18

Thrombolytic therapy for evolving acute myocardial infarction (AMI) reduces infarct size, preserves ventricular function, and reduces mortality. Intravenous streptokinase is commonly followed by approximately 50% patency of coronary arteries within 90 minutes and by reduction of mortality by 25%. Recombinant tissue plasminogen activator (rt-PA) is more potent for coronary arterial thrombolysis, producing both more rapid and more frequent recanalization (approximately 75% patency at 90 minutes) with a dose of 100 mg given over 3 hours. Side effects (mainly bleeding) associated with the use of streptokinase and rt-PA are not markedly different. That the higher efficacy of rt-PA would translate into a larger reduction of mortality is suggested by the results of several small trials but remains to be confirmed in well-designed comparative clinical trials. This question has not been adequately answered by the recent International rt-PA/streptokinase mortality trial and the International Study on Infarct Survival (ISIS-3) study, because of concerns with respect to the role of conjunctive intravenous heparin administration and the dose of rt-PA used in ISIS-3. All available thrombolytic agents still have significant shortcomings, including the need for large doses to be maximally efficient, a limited fibrin specificity, and a significant associated bleeding tendency. New developments toward improved efficacy and fibrin-specificity of thrombolytic agents include the use of mutants of rt-PA, chimeric rt-PA or single chain urokinase plasminogen activator molecules, and antibody-targeted thrombolytic agents. Some of these artificial plasminogen activators have a 5- to 10-fold increased potency (thrombolytic activity per unit dose), but whether they are safe enough to be clinically useful remains to be established. The conjunctive use of anticoagulants and antiplatelet agents with thrombolytic agents increases their efficacy to an extent that monotherapy with a plasminogen activator alone is no longer tenable. Heparin and aspirin are only moderately efficient for acceleration of lysis and prevention of reocclusion, but are relatively safe. More selective thrombin inhibitors and antiplatelet agents are more potent, but their safety remains to be confirmed. Continued investigation in this area will provide new insights and promote progress toward the development of the ideal thrombolytic therapy, characterized by maximized stable coronary arterial thrombolysis with minimal bleeding.
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PMID:Designing thrombolytic agents: focus on safety and efficacy. 172 81

An experimental cerebral embolic model was prepared by an injection of [125I]fibrin clot particles (20-100 microns) into the left internal carotid artery in rats, and the changes in radioactivity of the brain were continuously monitored by a gamma-ray detector. The autoradiograms of the caput transections showed the existence of emboli in small vessels of the left hemicerebrum. After the injection of [125I]fibrin clots, the radioactivity spontaneously decreased to a half of the initial radioactivity at 90 min. The decrease in radioactivity which represented the embolus dissolution was markedly suppressed by an antiplasmin agent, trans-4-aminomethyl cyclohexane carboxylic acid, indicating that the endogenous fibrinolysis through the activation of plasminogen is generated in the cerebral small vessels after the embolization. Consecutive injection of fibrin clots caused a summation of the radioactivity and decreased the rate of dissolution at every embolus preparation. The thrombolytic agents were infused via the left internal carotid artery for 30 min after the second successive injection of fibrin clots. Although the spontaneous dissolution of emboli was observed during the infusion of saline, tissue plasminogen activator (t-PA) as well as urokinase plasminogen activator (u-PA) produced a further dissolution. Approximately half of the emboli disappeared 60 min after the infusion of t-PA at a dose of 75 micrograms/kg and at a dose of 10000 IU/kg, respectively.
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PMID:Thrombolytic effect of tissue plasminogen activator in a cerebral embolic model. 180 87

We determined the plasma levels of tissue plasminogen activator (t-PA), plasminogen activator inhibitor (PAI) activity and their antigen levels including urokinase plasminogen activator (u-PA) in 33 male and 27 female normal subjects. Males had mean t-PA activity of 0.50 iu/ml which was significantly lower (p less than 0.01) than the females 0.64 iu/ml. Males had higher (p less than 0.001) mean PAI activity (15.5 AU/ml) as compared to females 10.3 AU/ml. The respective mean levels of t-PA and PAI antigen were significantly higher (p less than 0.01) in males (8.1 ng/ml and 17.6 ng/ml) than in females (6.2 ng/ml and 12.1 ng/ml). The mean u-PA level in males was 1.54 ng/ml which was significantly higher (p less than 0.01) than in females with 1.02 ng/ml. In post-venous occlusion studies, females had a greater mean response of 8.6 fold in t-PA activity as compared to males with a mean of 4.5 fold increase. The mean t-PA antigen response in males was 2.0 fold increase as compared to 2.6 fold increase in the females. No significant responses were seen in both sexes in either PAI activity or antigen levels when compared with the resting state. In zymography studies, free t-PA, its inhibitor complexes and u-PA were demonstrated in the euglobulin fractions of stored plasma. This study demonstrates that significant differences in t-PA, u-PA and PAI exist between male and female subjects which should be taken into account when determining their levels in clinical conditions.
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PMID:Plasminogen activators t-PA, u-PA and its inhibitor (PAI) in normal males and females. 180 23


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