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At least 523 records · Page 29Linked to original sources
PubMed1993

Epithelial glycoprotein-330 mediates endocytosis of plasminogen activator-plasminogen activator inhibitor type-1 complexes.

Epithelial glycoprotein 330 (gp330) is structurally similar to the multifunctional alpha 2-macroglobulin receptor/low density lipoprotein receptor-related protein (alpha 2MR/LRP), gp330 and alpha 2MR/LRP bind Ca2+ with high affinity, and both receptors bind and mediate endocytosis of alpha 2MR-associated protein (RAP). In the present report, we describe that affinity-purified gp330 from rabbit renal cortex binds plasminogen activator inhibitor type-1 (PAI-1) complexed with urokinase-type plasminogen activator (uPA). alpha 2M-methylamine, which binds with high affinity to alpha 2MR/LRP, did not bind to gp330. The apparent Kd for binding of uPA.PAI-1 complexes was about 0.8 nM at 4 degrees C. The binding was calcium-dependent and inhibited by recombinant RAP (rRAP) and tissue type plasminogen activator-PAI-1 complexes. Thin sections of rabbit renal proximal tubules bound 125I-labeled uPA.PAI-1 and rRAP in the apical part of proximal tubules corresponding to the localization of gp330. The binding of 125I-uPA.PAI-1 complexes in tubules was abolished by excess unlabeled rRAP, and a rRAP-inhibitable endocytosis and degradation of labeled uPA.PAI-1 complexes was demonstrated by perfusion of isolated rabbit proximal tubules. The results establish an endocytotic function of gp330 and suggest that gp330 is an important component of the fibrinolytic system in gp330-containing epithelial as found in, for example, kidney and lung.

Amino Acid Sequence↗
PubMed1990

Analysis of fibronectin, plasminogen activators and plasminogen in tear fluid as markers of corneal damage and repair.

Corneal damage of various origins initiates a series of processes which lead to repair but also tend to perpetuate the damage; healing thus depends on the prevalence of repair over progression processes. The plasminogen/plasmin system has an important impact on this process, particularly by degrading the extracellular matrix components with resulting interference of the repair processes. This paper presents the immunoblotting analysis of fibronectin, tissue and urokinase-type plasminogen activators and plasminogen/plasmin in the tear fluid of control subjects and patients affected by various ocular pathologies (corneal ulcers, thermal or chemical burns, herpetic keratitis). A significant modification was noted in the protein profiles of fibronectin, tissue and urokinase-type plasminogen activators and plasminogen/plasmin in the cases of corneal ulcers and thermal or chemical burns relative to the pattern observed in the control subjects, while in cases of herpetic keratitis, only plasminogen/plasmin showed slight variations. The altered protein patterns gradually normalized during therapeutic treatment and, at remission, coincided with those of the control subjects.

Adult↗
PubMed1995

Phosphorylation of human plasminogen activators and plasminogen.

Plasminogen (PG), urokinase-type plasminogen activator (u-PA) and tissue-type PA (t-PA) are the main molecules involved in fibrinolysis and in many other physiological and pathological processes. In the present study we report that human t-PA, purified from human melanoma cells, and PG, purified from human plasma, both contain P-Tyr residues, as revealed by immunoblotting analyses with monoclonal anti-P-Tyr antibodies. In addition HPLC amino acid analysis of acid-hydrolyzed t-PA, PG and u-PA, shows that: (i) P-Ser and P-Tyr residues are present in t-PA; (ii) P-Thr and P-Tyr are present in PG; (iii) P-Ser, P-Thr and P-Tyr are present in u-PA. The utilization of monoclonal anti-P-Ser and anti-P-Thr antibodies in immunoblotting experiments has confirmed these data which indicate that phosphorylation is a common feature of PAs and of PG.

Antibodies, Monoclonal↗
PubMed1989

Tissue plasminogen activator-induced secretion of type-1 plasminogen activator inhibitor in cultured human fibroblasts.

Tissue plasminogen activator (t-PA) regulation of type-1 plasminogen activator inhibitor (PAI-1) secretion by WI-38 human fibroblasts was investigated utilizing a specific ELISA to measure PAI-1 antigen levels. Incubation of confluent fibroblasts with t-PA in serum-free medium resulted in a concentration and time-dependent increase in the secretion of PAI-1, with the maximum response (a two-fold increase) observed following a 4 hour incubation with 0.1 microM t-PA. This t-PA effect was reduced by cycloheximide, suggesting that the involvement of specific protein synthesis, and by inhibitors of t-PA's enzymatic activity, suggesting a requirement for a free catalytic site. The t-PA effect could not be attributed to endotoxin contamination. Increased levels in cell-associated PAI-1 were also detected following incubation of fibroblasts with t-PA. This previously undescribed effect, although seen at relatively high concentrations of t-PA, may have important biological implications.

Cells, Cultured↗
PubMed1992

Reversible interactions between plasminogen activators and plasminogen activator inhibitor-1.

We have shown that the urokinase (UK) kringle domain contains a high-affinity plasminogen activator inhibitor-1 (PAI-1) binding site, responsible for the 10-fold faster complex formation between UK and PAI-1 than between PAI-1 and low-molecular-weight urokinase (LMWUK). Complex formation between UK and PAI-1, but not between LMWUK and PAI-1, was suppressed 10-fold in the presence of peptide U-107 derived from the UK kringle domain. Peptide U-373 derived from the UK catalytic domain slowed complex formation between UK and PAI-1 and also LMWUK and PAI-1. Inactivation of tissue-type plasminogen activator (tPA) by PAI-1 was slowed 10-fold in the presence of peptides derived from the tPA finger and kringle-2 domains. DFP-inactivated (DIP) UK and both forms of DIP-tPA inhibited PAI-1 binding to U-107 and to U-373 whereas single-chain urokinase-type PA (scuPA) was unable to compete with either peptide for PAI-1 binding. These data suggest that the reversible PAI-1 binding site in the UK A-chain plays a role in the rapid association with PAI-1 as important as those that reside in the tPA A-chain and that reversible PAI-1 binding sites are expressed on the surface of UK upon conversion from scuPA, in contrast to tPA.

Amino Acid Sequence↗
PubMedDate not supplied

Sex-related differences of plasminogen activator activity and plasminogen activator inhibition in the gastric wall after chronic ethanol consumption: effect of orchidectomy or ovariectomy.

Plasminogen activator activity (PAA), tissue-type PA (t-PA) antigen level, plasminogen activator inhibition (PAI), and plasmin inhibition (PI) showed no sex-dependent differences in the stomach of the rat. Chronic ethanol consumption induced an increase of PAA and t-PA antigen and a decrease of PAI (urokinase-type PA [u-PAI]) and PI in the body and pyloric region (PI only in the pyloric region). PAA increase and u-PAI decrease in the pyloric region were greater in the male than in the female. Orchidectomy, but not ovariectomy, induced effects similar to those of ethanol. The effects of orchidectomy and chronic ethanol consumption on gastric PAA, t-PA antigen, and PAI were additive. An increased PAA and decreased PAI or PI in the stomach in cases of hypogonadism, particularly if this deficiency is combined with chronic ethanol consumption, might influence the susceptibility to pathological conditions related to or affected by the local fibrinolytic activity (PAA, PAI, or PI).

Alcoholism↗
PubMed1988

Kinetic analysis of covalent hybrid plasminogen activators: effect of CNBr-degraded fibrinogen on kinetic parameters of Glu1-plasminogen activation.

The kinetic parameters of three activator species of Glu1-plasminogen (Glu1-Plg) were compared in their reaction at pH 7.4 and 37 degrees C, in the presence and absence of CNBr-digested fibrinogen (CNBr-Fg). The urokinase- (u-PA-) derived covalent hybrid activator PlnA-u-PAB had an apparent Michaelis constant (Kplg) of 7.44 microM, a catalytic rate constant (kplg) of 51.1 min-1, and a second-order rate constant (kplg/Kplg) of 6.87 microM-1 min-1. The tissue plasminogen activator (t-PA) derived covalent hybrid activator PlnA-t-PAB was characterized by a Kplg of 3.33 microM, a kplg of 1.03 min-1, and a kplg/Kplg of 0.309 microM-1 min-1. The kplg/Kplg values for the parent u-PA and t-PA activators were 6- and 16-fold higher than the respective hybrids, mainly due to an approximately 10-fold increase in the apparent Kplg for the hybrids. In the presence of CNBr-Fg, the increase of the kplg/Kplg values for u-PA and its hybrid was 1.1-fold, but for t-PA and its hybrid, the increases were 7- and 12-fold, respectively. In both the absence and presence of CNBr-Fg, activator t-PAB had an apparent Kplg of 19.1 and 27.6 microM and a kplg of 2.9 and 5.0 min-1, respectively. The increase in the kplg/Kplg value with CNBr-Fg was 1.2-fold. The streptokinase- (SK-) derived activators Glu1-plasmin.SK (Glu1-Pln.SK), Val442-Pln.SK, and Val561-Pln.SK had apparent Kplg values of 0.458, 0.268, and 0.121 microM and kplg values of 20.0, 126.0, and 63.3 min-1, respectively. In the presence of CNBr-Fg, the first two activators showed an approximately 1.4-fold increase and the last showed a 1.4-fold decrease in their kplg/Kplg values. The catalytic efficiency (kplg/Kplg) of the various activator species fell in the decreasing order SK greater than u-PA greater than t-PA, in either the presence or absence of CNBr-Fg. CNBr-Fg enhanced significantly the activities of only two activators, t-PA and PlnA-t-PAB.

Amidohydrolases↗
PubMed2002

Annexin II: a plasminogen-plasminogen activator co-receptor.

Fibrinolysis is a precisely orchestrated process in which fibrin-containing thrombi are solubilized. Several receptors regulate this process by localizing proteolytic activity to the cell surface. One such receptor is annexin II, a calcium and phospholipid-binding protein. Annexin II serves as a profibrinolytic coreceptor for both plasminogen and tissue plasminogen activator on the surface of endothelial cells and facilitates the generation of plasmin. The dysregulation of fibrinolytic assembly on endothelial cells may lead to atherothrombotic disease. In addition to its role in fibrinolysis at the surface of endothelial cells, annexin II may play other potential cellular roles. For example, the overexpression of annexin II on the surface of leukemic cells and cell lines derived from acute promyelocytic leukemia correlates with both the clinical manifestation of bleeding and the in vitro ability of the leukemic cells to generate plasmin. The abundant presence of annexin II on the surface of other cell types including monocytic cell lines and different cancer cells may contribute to their invasive potential through extracellular matrix either by generation of plasmin or, by plasmin-mediated proteolytic activation of other metalloproteinases. This dissolution of extracellular matrix may also cause the release of potent matrix-bound angiogenic factors such as VEGF and FGF. On the other hand, by increasing the pool of plasmin, a precursor to an important anti-angiogenic factor, angiostatin, and by fragmentation of collagen XVIII (a precursor to the anti-angigenic factor, endostatin) by plasmin-activated metalloproteases, annexin II could play a pivotal physiological role in the pro- and anti-angiogenic switch mechanism.

Annexin A2↗
PubMed2001

Decreased tissue plasminogen activator and increased plasminogen activator inhibitors and increased activator protein-1 and specific promoter 1 are associated with inhibition of invasion in human A375 melanoma deprived of tyrosine and phenylalanine.

We previously found that dietary tyrosine (Tyr) and phenylalanine (Phe) restriction significantly decreased the metastatic phenotype of the pigmented murine B16BL6 melanoma in vivo and decreased the in vitro invasion of these cells. Here we report that invasion and chemoinvasion through GFR Matrigel of the human amelanotic A375 melanoma also is significantly inhibited by Tyr and Phe deprivation in vitro. Deprivation of these two amino acids decreased the secretion and protein expression of tissue-type plasminogen activator (tPA) while expression and secretion of plasminogen activator inhibitor (PAI-1 and PAI-2) were increased. Moreover, nuclear extracts of Tyr- and Phe-deprived cells exhibited increased binding of the transcription factors, activator protein-1 (AP-1) and specific promoter-1 (Sp1), to consensus oligonucleotides as determined by electrophoretic mobility shift assay. Nuclear binding activity to the oligonucleotide consensus sequence for AP-1 was inhibited by antibody against c-Fos and more effectively inhibited by an antibody against c-Jun. We conclude that decreased invasion and chemoinvasion of A375 melanoma cells deprived of Tyr and Phe are related to decreased secretion of tPA and increased secretion of PAIs. Increased AP-1 and Sp1 binding implicates these transcription factors in the regulation of PAI expression.

Cell Adhesion↗
PubMedDate not supplied

Plasminogen activators (t-PA and u-PA) and plasminogen activators inhibitors (PAI-1 and PAI-2) in some myeloproliferative syndromes.

INTRODUCTION: Clinical observations and laboratory data indicate that patients with myeloproliferative syndrome (MPS) have hemostasis disorders that manifest with haemorrhagic diathesis or thrombotic disease. The role of fibrinolytic system is not clear in the pathomechanism of the disorders. In the study we aimed to evaluate fibrinolysis system in blood plasma of the patients with selected myeloproliferative syndromes on the basis of examinations of plasminogen activators (tissue--t-PA and urokinase-type--u-PA) and type 1 and type 2 plasminogen activator inhibitors (PAI-1 and PAI-2). MATERIAL AND METHODS: Forty-two patients (F/M 28/14) aged 36-78 years (average age--54 years) were enrolled into the study. Among the patients were 20 individuals with chronic myeloid leukaemia (CML), 17 with essential thrombocytemia (ET) and 5 with myelofibrosis (MF) treated in Provincial Haematological Outpatient Clinic in Bydgoszcz. Forty healthy volunteers (F/M 30/10) aged 24-65 (average 53) were included in control group. In citrate venous blood, the following parameters were determined: concentrations of antigen t-PA, u-PA, PAI-1, PAI-2, concentration of plasmin-alpha-2-antiplasmin complexes (PAP) determined with the use of ELISA technique, PAI-1 activity with amidolytic method, euglobulin lysis time (ELT) according to Kowarzyk-Buluk and fibrinogen/fibrin degradation products (FDP) concentration with the use of Merskey's method. RESULTS: Performed evaluations show that besides normal ELT elevated concentrations of FDP and PAP complexes occur in the blood of patients with myeloproliferative syndromes (MPS.). In studied myeloproliferative syndromes, high concentration of PAI-1 Ag and very low activity of PAI-1 were observed. In the patients with MPS intensified plasminogenesis and increased fibrin degradation were demonstrated. The role of granulocyte elastase is considered in activation of fibrinolysis system.

Adult↗
PubMed1991

The interaction of plasminogen activator inhibitor 1 with plasminogen activators (tissue-type and urokinase-type) and fibrin: localization of interaction sites and physiologic relevance.

Plasminogen activator inhibitor 1 (PAI-1), an essential regulatory protein of the fibrinolytic system, harbors interaction sites for plasminogen activators (tissue-type [t-PA] and urokinase-type [u-PA]) and for fibrin. In this study, anti-PAI-1 monoclonal antibodies (MoAbs) were used to identify interaction sites of PAI-1 with these components. The binding sites of 18 different MoAbs were established and are located on five distinct "linear" areas of PAI-1. MoAbs, binding to two distinct areas of PAI-1, are able to prevent the inhibition of t-PA by PAI-1. In addition, two interaction sites for fibrin were identified on PAI-1. The area located between amino acids 110 and 145 of PAI-1 contains a binding site for both components and its significance is discussed in the context of the t-PA inhibition by fibrin-bound PAI-1. Subsequently, the MoAbs were used to assess the role of platelet-PAI-1 in clot-lysis. An in vitro clot-lysis system was used to demonstrate that clot-lysis resistance is dependent on the presence of activated platelets and that PAI-1 is a major determinant for lysis-resistance. We propose that, upon activation of platelets, PAI-1 is fixed within the clot by binding to fibrin and retains its full capacity to inhibit t-PA and u-PA.

Antibodies, Monoclonal↗
PubMed1990

Plasminogen activator inhibitors type 1 and type 2 and plasminogen activators in amniotic fluid during pregnancy.

Plasminogen activator inhibitor activity (PAI), PAI-1 and PAI-2 antigen, and other fibrinolytic parameters were evaluated in amniotic fluid during normal pregnancy and compared with that obtained in plasma of pregnant women. The results indicate the presence of both PAI-1 and PAI-2 in amniotic fluid during normal pregnancy. In amniotic fluid, PAI-1 antigen levels increased from 194 +/- 109 ng/ml (first trimester) to 640 +/- 396 ng/ml (third trimester) and PAI-2 antigen levels increased from 72 +/- 57 ng/ml to 173 +/- 97 ng/ml. In contrast, a decrease in tissue-type plasminogen activator (t-PA) antigen level was observed during pregnancy. The PAI-1 levels in amniotic fluid were significantly higher than the PAI-1 levels in plasma of women at a similar gestational age. However, PAI activity, measured using single chain t-PA, was lower in amniotic fluid than in plasma of normal pregnant women. The PAI activity/PAI-1 antigen ratio in amniotic fluid after activation by a denaturing agent increased from 0.003 +/- 0.004 to 0.059 +/- 0.018. These results indicate that high levels of PAI-1 are present in amniotic fluid and suggest that this PAI-1 is present in a latent form that can be reactivated, at least partially, by a denaturing agent.

Amniotic Fluid↗
PubMed1989

Plasminogen activators and plasminogen activator inhibitors in liver deficiencies caused by chronic alcoholism or infectious hepatitis.

Plasma concentrations of tissue-type plasminogen activator (t-PA), urokinase (u-PA), plasminogen activator inhibitor 1 (PAI-1) and PAI-2 were studied in 53 patients with liver deficiency caused by chronic alcoholism (n = 40), viral hepatitis (n = 10) or malignant disease of the liver (n = 3) and compared to that of a control group (n = 20) of healthy subjects. u-PA and PAI-1 levels were significantly increased in all patients with chronic alcoholism, whereas high t-PA was only observed in combination with disturbed liver function tests or with liver cirrhosis (two and six-fold above control values, respectively). A good correlation was observed between t-PA and gamma glutamyl transferase (r = 0.615; p less than 0.001). In patients with infectious hepatitis or with malignant disease of the liver t-PA was normal whereas u-PA and PAI-1 were increased. PAI-2 levels were close to or below the detection limit (15 ng/ml) in the control group and in most patients. However, in two patients with alcohol induced cirrhosis PAI-2 levels were approximately 45 ng/ml and in one patient with hepatocarcinoma even 66 ng/ml. Thus, in liver disease, marked elevations of t-PA, u-PA and PAI-1 levels may occur, with increased PAI-1 as an early marker of liver defects and t-PA a marker of severe liver defects.

Female↗
PubMed1993

Mechanism of action of angiostatic steroids: suppression of plasminogen activator activity via stimulation of plasminogen activator inhibitor synthesis.

Recently, a novel class of angiostatic steroids which block angiogenesis in several systems has been described. Since the elaboration of proteases is believed to be an important component of angiogenesis, we tested whether these steroids blocked the fibrinolytic response of endothelial cells to the angiogenic protein, basic fibroblast growth factor [bFGF]). Cultured bovine aortic endothelial (BAE) cells were incubated with bFGF and/or medroxyprogesterone acetate (MPA), an angiostatic steroid which has been shown to inhibit vascularization, collagenolysis, and tumor growth. When bFGF (3 ng/ml) was added to confluent monolayers of BAE cells, plasminogen activator (PA) activity in the medium was increased threefold. In contrast, MPA at 10(-6) M, 10(-7) M, 10(-8) M, and 10(-9) M decreased PA levels in the medium by 83%, 83%, 75%, and 39%, respectively. The stimulation of PA levels in BAE cells by bFGF (3 ng/ml) was abrogated by the presence of 10(-6) M MPA. This decrease in PA activity was found to be mediated by a significant increase in plasminogen activator inhibitor type-1 (PAI-1) production. MPA, therefore, negated one of the important enzymatic activities associated with the angiogenic process. In contrast to the decreased levels of secreted PA in cultures exposed simultaneously to MPA and bFGF, cell-associated PA levels remained high, consistent with earlier observations indicating that PAI-1 does not inhibit cell-associated PA. Thus, angiostatic steroids may exert their inhibitory effects on angiogenesis by increasing the synthesis of PAI-1. This, in turn, inhibits PA activity and, therefore, plasmin generation, which is essential for the invasive aspect of angiogenesis.

17-alpha-Hydroxyprogesterone↗
PubMedDate not supplied

Mechanism of the stimulatory effect of 6-aminohexanoic acid on plasminogen activation by streptokinase or tissue plasminogen activator: the role of chloride.

Studies were conducted on the mechanism of the stimulatory effect of 6-aminohexanoic acid (6-AH) during the in vitro activation of human glutamic plasminogen (Glu-Plg) by streptokinase or by tissue plasminogen activator (t-PA) and the possible role of the addition of physiological concentrations of NaCl to the buffer solution. Enhancement by 6-AH was investigated by measuring the rate of plasmin generation using chromogenic substrate H-D-glu-phe-lys-pNA (S-2403). Control studies using plasmin showed that the addition of 6-AH at concentrations below 20 mM did not significantly affect the initial rate of the amidolytic activity of plasmin with or without the addition of NaCl to 0.05 M Tris buffer (pH 7.4). On the other hand, addition of NaCl to the buffer slowed down the initial rate of activation of Glu-Plg by streptokinase or by t-PA while increasing the percent enhancement by 6-AH when compared with the controls. The ratios of the initial rates of plasmin generation in the presence or in the absence of 6-AH were plotted against the inverse of the volume fraction of Glu-Plg, streptokinase or t-PA after serial dilutions. The results showed that when the activation reactions were performed in 50 mM of Tris buffer (pH 7.4), the enhancements by 6-AH were related to its interaction with streptokinase or t-PA, while using the same Tris buffer containing 0.6 % NaCl, the enhancements by 6-AH were related to its interaction with both Glu-Plg and streptokinase or t-PA. However, upon increasing the NaCl to 0.9%, the results showed that the enhancements by 6-AH of the activation of Glu-Plg by streptokinase or t-PA were related to its interaction with Glu-Plg. The results suggested that changes in the concentrations of NaCl play a regulatory role during the activation process.

Aminocaproic Acid↗
PubMed1988

Immunohistochemical localization of urokinase-type plasminogen activator in Sertoli cells and tissue-type plasminogen activator in spermatogenic cells in the rat seminiferous epithelium.

The occurrence of plasminogen activators of the urokinase-type (u-PA) and tissue-type (t-PA) at various stages of the epithelial cycle was studied immunohistochemically in rat seminiferous tubule segments. u-PA immunoreactivity was detected exclusively at stages VII and VIII in Sertoli cells, displaying a distinct granular cytoplasmic staining. t-PA immunoreactivity was found during mid- and late pachytene and diakinesis (stages VII-XIII) in spermatogenic cells, displaying a granular cytoplasmic staining with maximal intensity in stages IX-XIII. The specificity of the stainings was supported by staining controls, including absorption of the antibodies with purified preparations of the activators. It was also supported by zymographic studies of the occurrence of u-PA and t-PA in extracts of tubular segments at different stages of the cycle, isolated by transillumination-assisted microdissection. The possible functions of the two types of plasminogen activators in the seminiferous epithelium are discussed.

Animals↗
PubMed1986

Effects of fibrin on the enhanced activation of plasminogen by urokinase and tissue plasminogen activator: role of cross-link.

When human plasma was activated by urokinase (UK) in the presence of thrombin, thrombin plus Ca++, Ca++ or in their absence and the plasmin activity was measured by the hydrolysis of S-2251, plasmin activity was higher in the presence of cross-linked or non cross-linked plasma clot. The results of similar experiments utilizing plasma after severe exercise indicated that the hydrolysis of S-2251 by plasma containing tissue plasminogen activator (t-PA) was also higher in cross-linked or non cross-linked plasma clot. Fibrinolysis was faster in thrombin-induced plasma clot, but was later shown significantly in plasma clot induced by thrombin and Ca++, whereas practically no fibrinogenolysis was shown in plasma. When Glu-plasminogen (Glu-plg) was activated by UK in the presence of cross-linked or non cross-linked fibrin and alpha 2 antiplasmin (alpha 2AP), fibrinolysis was faster in cross-linked fibrin than non cross-linked fibrin in the presence of alpha 2AP. No fibrinogenolysis was shown either. Plasmin activity measured by the hydrolysis of S-2251 was also higher in cross-linked or non cross-linked fibrin than in fibrinogen in the presence of alpha 2AP. These results indicate that enhanced activation of Glu-plg by UK or t-PA in the presence of fibrin was a more significant event than the inactivation of plasmin in the plasma clot or purified clot by alpha 2AP cross-linked to fibrin.

Calcium↗
PubMed1988

Bolus dose response characteristics of single chain urokinase plasminogen activator and tissue plasminogen activator in a dog model of arterial thrombosis.

Tissue plasminogen activator (t-PA) and single chain urokinase-plasminogen activator (scu-PA) are relatively "fibrin-specific" thrombolytic drugs with short plasma half lives of 6-8 minutes. Most treatment regimens with these agents utilize a bolus injection followed by continuous drug infusion, usually combined with anticoagulant therapy. The purpose of this study was to establish the dose-response characteristics for scu-PA and t-PA, when given as a single intravenous bolus injection, in a dog model of arterial thrombosis. Eight groups of 6 dogs each were given one of the following doses of scu-PA (mg/kg): 0.20, 0.50, 1.00, 2.00; or t-PA: 0.05, 0.10, 0.20; or an equivalent amount of saline (control group). All doses were given as a single bolus injection 60 minutes after formation of a totally occlusive femoral artery thrombus. Thrombolysis was measured by monitoring the continuous decrement of 125I activity from a radiolabelled thrombus. Ninety minutes after drug injection, all scu-PA treated dogs showed greater thrombolysis (30%, 45%, 56%, and 67%, respectively) than the control group (15%, p less than 0.01). The 0.10 and 0.20 mg/kg t-PA treated dogs showed greater thrombolysis (35% and 49%, respectively) than the control group (15%, p less than 0.01). Both scu-PA and t-PA caused a partial and dose-dependent decrease in alpha 2-antiplasmin activity but scu-PA caused a greater depletion (72% vs. 18%, respectively, p less than 0.05) at 60 minutes after the highest dose of drug administration. Both drugs showed a longer than expected thrombolytic effect based upon the known half lives. Neither drug caused significant changes in the prothrombin time, activated partial thromboplastin time, thrombin time, hematocrit, platelet count, or fibrin degradation product concentration. Single bolus injections of scu-PA and t-PA produce safe and effective thrombolysis in this dog model of arterial thrombosis.

Animals↗