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PubMed1995

The impact of heparin concentration and activated clotting time monitoring on blood conservation. A prospective, randomized evaluation in patients undergoing cardiac operation.

A whole blood hemostasis system (Hepcon) provides both activated clotting time and accurate whole blood heparin concentration measurements via an automated protamine titration method. This study was designed to prospectively evaluate the impact of heparin and protamine administration using this system on the incidence and treatment of bleeding after cardiopulmonary bypass. Two hundred fifty-four patients requiring cardiopulmonary bypass were enrolled in this prospective study over a 7-month period. Patients treated with antifibrinolytic agents (aprotinin, epsilon-aminocaproic or tranexamic acid) were excluded. Patients were randomly assigned to either a control (n = 127) or intervention (n = 127) group. For control patients, the anticoagulation protocol consisted of an initial fixed dose of 250 U/kg of heparin, and additional 5000 U heparin doses were administered if the activated clotting time was less than 480 seconds. Heparin was neutralized with an initial fixed dose of protamine (0.8 mg protamine per milligram total heparin). For the intervention group, an initial dose of heparin was based on an automated heparin dose-response assay. Additional heparin doses were administered if the heparin concentration was less than the reference concentration or for an activated clotting time less than 480 seconds. The protamine dose was based on the residual heparin concentration. Treatment of excessive bleeding after cardiopulmonary bypass was based on an algorithm using point-of-care testing with whole blood prothrombin time, activated partial thromboplastin time, heparinase activated clotting time, and platelet count. No differences between the two treatment groups were identified in reference to demographic factors, preoperative anticoagulant medications, preoperative coagulation data, number of reoperations, or combined procedures and duration of cardiopulmonary bypass. Indirect evidence for coagulation factor consumption was demonstrated in control patients by more prolonged whole blood prothrombin time and activated partial thromboplastin time values after cardiopulmonary bypass when compared with values obtained in the intervention group. Patients in the intervention cohort received greater doses of heparin (intervention: 612 +/- 147, control: 462 +/- 114 U/kg, p < 0.0001) and had lower protamine to heparin ratios (intervention: 0.70 +/- 0.64, control: 0.94 +/- 0.21, p = 0.0001) compared with control patients. Patients in the intervention cohort received significantly fewer platelet (intervention: 1.7 +/- 3.6 U, control: 3.7 +/- 6.7 U, p = 0.003), plasma (intervention: 0.4 +/- 1.3 U, control: 1.4 +/- 2.5 U, p = 0.0001), and cryoprecipitate units (intervention: 0.0 +/- 0.0 U, control: 0.2 +/- 1.2 U, p = 0.04) during the perioperative interval than control patients.(ABSTRACT TRUNCATED AT 400 WORDS)

Aged↗
PubMed1994

Evaluation of desmopressin for dental extractions in patients with hemostatic disorders.

We evaluated the effectiveness of desmopressin to control bleeding of patients with coagulation defects during dental surgery. Thirty-five patients, mainly with moderate and mild hemophilia and Willebrand disease, were undergoing dental extractions (over 80 extractions in total). Bleeding was successfully prevented in 28 patients with the use of a combined treatment incorporating IV desmopressin, an antifibrinolytic agent (tranexamic acid), and local methods (surgical glue and compression techniques). Seven patients had a bleeding episode after dental extraction, which was controlled in two cases by repeated injection of desmopressin and in another two by local methods; Factor VIII substitutive treatment was needed in only three patients. Desmopressin offers an alternative to blood products to control bleeding risk in patients with moderate and mild coagulation defects. Our experience tends to specify the mode of administration of both desmopressin and the associated treatments. Our findings suggest that desmopressin can be used in conjunction with other treatments to prevent bleeding in patients with coagulation defects who undergo dental surgery. This work highlights the concept of multifactorial medical care of these patients in which desmopressin plays a major role.

Adolescent↗
PubMedDate not supplied

Ligneous conjunctivitis.

Ligneous conjunctivitis (McKusick 217090) is a rare form of chronic conjunctivitis characterized by the development of firm fibrin-rich, woody-like pseudomembraneous lesions mainly on the tarsal conjunctivae. Less frequently, similar lesions may occur on other mucous membranes of the body indicating that these manifestations are part of a systemic disease. Histopathological findings from affected humans and (plasminogen-deficient) mice indicate that wound healing, mainly of injured mucosal tissue, is impaired due to markedly decreased (plasmin-mediated) extracellular fibrinolysis. Pseudomembraneous lesions of the eyes and other mucosal tissue mainly contain clotted fibrin(ogen). Actually, systemic plasminogen deficiency has been linked to ligneous conjunctivitis in humans and mice. In one case, ligneous conjunctivitis has been induced by antifibrinolytic treatment with tranexamic acid. Further rare associated disorders of ligneous conjunctivitis are congenital occlusive hydrocephalus and juvenile colloid milium. This review outlines the historical background, clinical characteristics of ligneous conjunctivitis and its associated complications, histological abnormalities of pseudomembraneous lesions, inheritance, hemostasiologic and molecular genetic findings in affected patients, current treatment approaches, and the plasminogen-deficient mouse as an animal model.

Animals↗
PubMed2003

Acute coagulopathy after reperfusion of the liver graft in children correction with recombinant activated factor VII.

BACKGROUND: Several studies have proven that massive blood loss increases postoperative morbidity and mortality in liver graft recipients. Since we have successfully corrected coagulopathy preoperatively using an intravenous (IV) bolus of recombinant activated factor VII (rFVIIa) in 2 patients with fulminant liver failure, we observed that there was rapid reversal of preexisting advanced coagulopathy in another 40 patients with high risk for intraoperative bleeding by this treatment immediately before transplantation. Recently to control hemostasis we have administered rFVIIa also to patients presenting with acute coagulopathy and nonsurgical bleeding after graft reperfusion as described herein. MATERIALS AND METHODS: We have used rFVIIa in 7 children presenting with severe coagulopathy and nonsurgical bleeding after liver graft reperfusion. The dosage of rFVIIa ranged between 37 and 148 mcg/kg. An antifibrinolytic agent (aprotinin, tranexamic acid) was administered simultaneously. RESULTS: APTT before rFVIIa was 86.10 to 183 seconds, (mean, 132.1 +/- 39.88), after the bolus of rFVIIa 49.4 to 206.1 (mean, 112.7 +/- 58.53), and at the end of surgery 71.70 to 180 (mean, 110.3 +/- 40.98). INR after reperfusion was 1.82 to 3.91 (mean, 2.56 +/- 0.67), 1.03 to 1.92 (mean, 1.54 +/- 0.35) after rFVIIa, and 1.74 to 5.58 (mean, 2.64 +/- 1.35) at the end of surgery. Before rFVIIa administration intraoperative blood transfusions after graft reperfusion were 900 to 4200 mL of red blood cells (RBC) (0.82-5.4 total blood volume) and after reperfusion 0 to 1800 mL of RBC (0-2.5 TBV). No postoperative vascular complications were observed. CONCLUSIONS: A single dose of rFVIIa effectively reverses the severe coagulopathy developing after graft reperfusion, establishing effective hemostasis in liver transplant recipients without an increased risk of thrombotic complications.

Blood Coagulation Disorders↗
PubMed2001

Method to measure in vivo blood fibrinolytic activity with a (125)I-fibrin coated aorta loop validated with agents which affect blood fibrinolytic activity.

A functional animal model to measure in vivo the blood fibrinolytic activity and pharmacological-induced changes thereof are described. A (125)I-fibrin coated plastic loop is inserted in the rat aorta; the rate of label disappearance (sigmoid curve) is directly registered outside the animal with a gamma scintillation probe. The time needed to let disappear 50% of the removable-labeled fibrin is used as measure for the blood fibrinolytic activity. The direct advantage of this model is the absence of a blood or plasma clot: a thin labeled fibrin layer attached to the inner wall of the loop is in direct contact with the blood and is therefore sensitive to increased or decreased blood fibrinolytic activity. The total experiment needs about 60 min. Experiments with nontreated rats showed that, after an initial lag phase of about 10 min, the labeled fibrin started to disappear from the loop. A sigmoid pattern was obtained showing that about 20-30% of the coated-labeled fibrin is resistant to removal. Registration of the total curve of a nontreated (control or placebo) rat required about 30-40 min. The clinically used thrombolytics (intravenously administered) urokinase and t-PA showed a dose-dependent fibrinolytic activity resulting in increased removal of the bound (125)I-fibrin. Streptokinase was not active, which is in agreement with literature. Tranexamic acid, dexamethasone and endotoxin (inhibitors of fibrinolysis) showed dose-dependent inhibition of removal of the coated fibrin. Retinoic acid was tested as compound, which may enhance the blood fibrinolytic activity; retinoic acid was not found to be significantly active in this model. The disappearance of labeled fibrin is not sensitive to inhibitors of coagulation or platelet aggregation. This technically simple and fast model can thus be used to measure in vivo quantitatively the effects of pharmacological active compounds, which increase or decrease the blood fibrinolytic activity.

Animals↗
PubMed2002

Differences between neonates and adults in carbohydrate sequences and reaction kinetics of plasmin and alpha(2)-antiplasmin.

This study investigates reaction kinetics by slow-binding kinetics methods of both adult and fetal plasmin (Types 1 and 2) with adult and fetal alpha(2)-antiplasmin. In addition, carbohydrate sequences of Fetal and Adult Plasminogen Types 1 and 2, as well as fetal and adult alpha(2)-antiplasmin, were determined by mass spectrometric analysis. All curves of plasmin-alpha(2)-antiplasmin interaction followed the same pattern, indicating reversible slow-binding inhibition with an initial loose complex and a following tight complex. Differences between fetal and adult plasmin reactions with alpha(2)-antiplasmin were predominantly due to the initial loose complex. Values for K(i initial) in the reaction with adult alpha(2)-antiplasmin were 1.5 and 1.6 nM for Fetal Plasmin Types 1 and 2, respectively; compared to 0.3 and 0.7 nM for the corresponding adult types. Increasing concentrations of tranexamic acid resulted in a continuous increase of K(i initial) until a plateau was reached which was similar for all plasmin types. Almost identical values could be obtained when fetal alpha(2)-antiplasmin was used instead of adult alpha(2)-antiplasmin. Mass spectrometric analyses of the glycans present on plasminogen revealed a higher level of truncated N-glycans on the fetal material compared to the adult. The O-glycans of fetal and adult plasminogen were closely similar and only minor differences were observed between N-glycans of fetal and adult alpha(2)-antiplasmin. In conclusion, both fetal plasmin isoforms are less inhibited by alpha(2)-antiplasmin compared to the adult plasmin variants. These findings are important for the understanding of the physiology of the fibrinolytic system in neonates and provide further evidence that differences in glycosylation could be associated with marked effects on protein function.

Adult↗
PubMed2002

Plasminogen activator-plasmin system potentiates the proliferation of hepatocytes in primary culture.

BACKGROUND/AIMS: Liver regeneration after partial hepatectomy is thought to be regulated by various molecules including the components of the plasminogen activator (PA)-plasmin system. We have examined the role of fibrinolytic factors, i.e., tissue-type plasminogen activator (tPA) and urokinase-type plasminogen activator (uPA), and their substrate, plasminogen, in the proliferation of hepatocytes in primary culture. METHODS: Hepatocyte and nonparenchymal liver cells were isolated from Wistar strain rat by a method perfusing the liver with collagenase. DNA synthesis was assessed by measuring the incorporation of [3H]-thymidine into cellular DNA fraction. tPA, uPA and type-1 plasminogen activator inhibitor (PAI-1) gene expressions were measured by Northern blotting. PA activity was measured by fibrin/agarose plate method. RESULTS: Cellular density-dependent DNA synthesis was observed in the primary cultured hepatocytes; DNA synthesis was lower at high cell density (1.0 x 10(5) cells/cm(2)) than that at low cell density (0.2 x 10(5) cells/cm(2)). DNA synthesis in the hepatocytes cultured at a low cell density was increased by co-culture with nonparenchymal liver cells. Under these growth-stimulated culture conditions, tPA and uPA mRNAs were induced and up-regulated. On the contrary, the PAI-1 mRNA level was decreased under these conditions, and total PA activity was augmented accordingly. The synthetic plasmin inhibitor tranexamic acid, a competitive inhibitor for the plasmin molecule, and PASI-535, a plasmin active center-directed inhibitor, both suppressed hepatocyte proliferation in a dose-dependent fashion. Anti-plasmin antibody also suppressed hepatocyte proliferation. CONCLUSIONS: The up-regulation of PA activity for ensuring plasmin activity should be an important mechanism in the proliferation of hepatocytes.

Animals↗
PubMed2000

A simple screening assay for certain fibrinolysis parameters (FIPA).

Hemostasis, the system of generation and degradation of thrombi, consists of coagulation and fibrinolysis. Whereas global assays to study coagulation have existed for many years, there has been no simple, rapid, and economic routine test for the plasmatic fibrinolysis parameters plasminogen activator inhibitor-1, alpha2-antiplasmin, plasminogen, and aprotinin. Here a fast functional global assay for these plasmatic fibrinolytic parameters is presented. However, the present assay is not sensitive to physiological concentrations of prourokinase or tissue-type plasminogen activator. The following assay conditions have been found to be optimal: 50 microL of citrated plasma is incubated with 50 microL of 10 IU urinary-type plasminogen activator (urokinase)/mL, 1.1 mmol/L tranexamic acid, 1% polygelin, 0.1% Triton X-100, phosphate-buffered saline, pH 7.4, for 20 min at 37 degrees C (plasmin generation phase). Then 50 microL of 3 mmol/L HD-Nva-CHA-Lys-pNA, 1.05 mol/L KCl is added, and deltaA (405 nm)/10 min (37 degrees C) is determined, by using a microtiterplate reader (plasmin detection phase). The results are calibrated against pooled normal plasma (100% plasmatic fibrinolytic parameters activity). The intra- and interassay coefficients of variation have been found to be less than 5%. The detection limit (sensitivity) of the functional fibrinolysis assay is 5 % of the normal plasmatic fibrinolysis parameters activity. The normal plasmatic fibrinolysis parameters activity is 100%, sigma = 25%. The plasmatic fibrinolysis parameters activity correlates negatively (r = -0.684) with the plasminogen activator inhibitor-1 activity of patient samples. The plasmatic fibrinolysis parameters assay is a simple, rapid, and economic functional test for several clinical relevant fibrinolysis parameters.

Adolescent↗
PubMed1987

[Aorto-coronary bypass and defibrination after thrombolysis during the acute phase of myocardial infarct].

Coronary bypass was carried out in four patients who have received an intracoronary streptokinase infusion for acute myocardial infarction. Indications for emergency operation were a myocardial ischaemia time of less than 4 h and a slow flow in the reopened artery despite percutaneous transluminal coronary angioplasty. Two patients were in cardiogenic shock treated by inotropic drugs and intra-aortic balloon pump. In all cases, the level of fibrinogen was less than 1 g X l-1. During the operation, the fibrinolysis was stopped by the intravenous injection of aprotinine (3,000,000 U X 2) and tranexamic acid (15 mg X kg-1), the coagulation factors used by the fibrinolysis being replaced by fibrinogen (1 g per litre of blood volume) and fresh plasma (6 to 8 packs in function of the haemodynamic state). Patient heparinization was as usual (300 IU X kg-1). At the end of the cardiopulmonary bypass, after injection of protamine, clotting quality was good and the fibrinogen level was more than 1 g X l-1. In the postoperative period, blood loss was of little importance. Coagulation troubles due to therapeutic fibrinolysis were reversible. It was possible to return quickly the patient's coagulation state to normal, and so carry out emergency coronary arterial surgery in a defibrinated patient. The indications for surgery depended on cardiogenic factors only.

Angioplasty, Balloon↗
PubMed1997

Fibrinolytic inhibitors for cancer-associated bleeding problems.

This pilot study of 16 patients explored the use of two fibrinolytic inhibitors, tranexamic acid and aminocaproic acid, for the suppression of tumor-associated hemorrhage. The effects of such bleeding include anemia requiring transfusion, practical difficulties with dressings, and psychological morbidity from constant reminder of poor physical health. Cessation of bleeding occurred in 14 of the 16 patients treated. The average time until significant improvement in bleeding was just 2 days and the average time for complete cessation was 4 days. We conclude that fibrinolytic inhibitors are potentially useful agents in palliative care.

Adult↗
PubMed2006

Aprotinin; friend or foe? A review of recent medical literature.

Recent articles published in peer review journals have questioned the safety of using aprotinin in patients having heart surgery. Also, evidence has been published to suggest an increase in renal events in patients given aprotinin when compared to those where tranexamic acid was used. The present review will focus principally on the first of these articles in relation to previously published data and experience.

Aprotinin↗
PubMed1995

Treating menorrhagia in primary care. An overview of drug trials and a survey of prescribing practice.

Menorrhagia can be treated by drug therapy or surgery. General practitioners (GPs) can prescribe drugs to reduce menstrual blood loss as first-line treatment, referring patients for surgical treatment if drug therapy fails. This study examined the efficacy of drugs used to treat menorrhagia and surveyed British GPs to discover the extent to which they prescribed the most effective drugs for this condition. The results suggest that treatment of this condition in primary care falls short of desirable standards. A meta-analysis of randomized trials of drug therapy revealed wide differences in efficacy and side effects. The most effective drug (tranexamic acid) is little used by British GPs, whereas the least effective drug (norethisterone) is the most frequently prescribed.

Adult↗
PubMed2000

Protein production by osteoblasts: modulation by breast cancer cell-derived factors.

Breast cancer cells (BCC) frequently metastasize to bone where they may cause tumor-induced osteolysis (TIO). While the important eroding role of the osteoclasts in TIO is well admitted, the possibility that BCC and/or osteoblasts activated by tumoral factors could also directly degrade bone matrix in this pathology has been much less investigated. We show here that the net collagen amount produced in vitro by normal human osteoblasts and osteoblast-like cells was significantly reduced by culture medium conditioned by several BCC lines, including three newly isolated ones. There was no evidence for a decrease in collagen synthesis, as assessed by the production of the carboxyterminal propeptide of type I collagen. In contrast, the effect of BCC-derived medium on collagen amount was attenuated by inhibitors of matrix metalloproteinases (MMPs) as well as by tranexamic acid, an inhibitor of the plasminogen conversion to plasmin, while it was abolished in presence of the two kinds of proteinase inhibitors. This osteoblastic protein degradation activity appeared to be attributable to factors secreted by the osteoblasts as well as by BCC. These factors had molecular weights lower as well as higher than 10 kD. Our data suggest that besides the eroding action of osteoclasts, BCC- and osteoblast-derived MMPs and serine proteinases might play a direct role in bone collagen degradation in TIO.

Adenocarcinoma↗
PubMed2003

Menorrhagia: an update.

Menorrhagia is defined as a 'complaint of heavy cyclical menstrual bleeding occurring over several consecutive cycles'. Objectively it is a total menstrual blood loss equal to or greater than 80 ml per menstruation. It is estimated that approximately 30% of women complain of menorrhagia. Excessive bleeding is the main presenting complaint in women referred to gynecologists and it accounts for two-thirds of all hysterectomies, and most of endoscopic endometrial destructive surgery. Thus, menorrhagia is an important healthcare problem. Its etiology, investigation, medical and surgical management are described. In approximately 50% of cases of menorrhagia no pathology is found at hysterectomy. Abnormal levels of prostaglandins or the fibrinolytic system in the endometrium have been implicated. Effective medical treatments suitable for long-term use include intrauterine progestogens, antifibrinolytic agents (tranexamic acid) and nonsteroidal anti-inflammatory agents (mefenamic acid). Over the past decade there has been increasing use of endometrial destructive techniques as an alternative to hysterectomy. Their further refinement and the advent of fibroid embolization has increased the options available to women.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed1997

Proteinase inhibitors reduce basement membrane degradation by human breast cancer cell lines.

The relative importance of different proteinases, and their inhibition, in the breakdown of human endothelial basement membrane (BM) by MDA-MB-231 and MCF7ADR human breast cancer cell lines has been studied using 35S-labelled BM-coated 96-well culture plates. Basement membrane degradation (BMD) was independent of cell proliferation above the seeding density. Inhibitors of aspartic (pepstatin and PD 134678-0073) and cysteine proteinases (E64) had little effect on BMD under normal culture conditions, suggesting that cathepsins D, B and L have only a minor role. In contrast, inhibitors of urokinase-type plasminogen activator (uPA) and/or plasminogen activation to plasmin (aprotinin, amiloride, EACA, tranexamic acid, anti-uPA antibody) all reduced BMD by MDA-MB-231 cells by approximately 30-40%, but only in the presence of serum or plasminogen. BB94, an inhibitor of matrix metalloproteinases (MMPs), also reduced BMD by about 30% under these conditions but was similarly effective in serum-free medium. Combinations of BB94 with any of the uPA/plasminogen activation inhibitors in serum-containing medium had additive effects, while BB94 with pepstatin and E64 under serum-free conditions reduced BMD to 16% of control. Serum-containing conditioned medium exhibited appreciable BMD, largely due to aprotinin-inhibitable activity. Although small reductions in cell proliferation were seen with some inhibitors, the combination of BB94 with E64 or E64d reduced the cell population by about 60% under serum-containing conditions. These in vitro observations suggest that combinations of proteinase inhibitors, particularly of uPA/plasminogen activation and MMPs, may merit clinical evaluation as potential antimetastatic therapy for breast cancer.

Basement Membrane↗
PubMed1998

Antithrombotic activity of a monoclonal antibody inducing the substrate form of plasminogen activator inhibitor type 1 in rat models of venous and arterial thrombosis.

1. Elevated plasminogen activator inhibitor 1 (PAI-1) is a risk factor for thrombosis, and inhibitors of the interaction between PAI-1 and tissue plasminogen activator (t-PA) have antithrombotic and prothrombolytic activity in animals. We describe the antithrombotic effects in the rat of a monoclonal antibody (MA33H1) which converts PAI-1 to a non-inhibitory substrate. 2. The activity of MA33H1 against rat PAI-1 was confirmed using two-chain t-PA and a chromogenic substrate. MA33H1 was evaluated in rat venous (thromboplastin + stasis in the abdominal vena cava) and arterial (electric current applied to a carotid artery) thrombosis models. The effects on tail-transection bleeding time were studied. 3. MA33H1 at 100 ng ml(-1) inhibited both human (44.1%) and rat PAI-1 (49.7%). This effect was concentration-dependent. Its effect on human PAI-1 was not significantly inhibited by 1 microg ml(-1) fibrin or a approximately 7 fold molar excess of vitronectin (1 nM). Inhibition of rat PAI-1 was unchanged by fibrin, but vitronectin reduced inhibition from 0.5 nM. 4. In the venous thrombosis model, MA33H1 significantly reduced thrombus weights by 38 and 58.6% at 50 and 100 microg kg(-1) min(-1) i.v. respectively. This effect was inhibited by tranexamic acid. In the arterial model, MA33H1 significantly increased the delay to occlusive thrombus formation by 58 and 142% at 50 and 100 microg kg(-1) min(-1) i.v., and did not affect bleeding time at 300 microg kg(-1) min(-1) i.v. 5. Thus, a monoclonal antibody which transforms PAI-1 to a t-PA substrate prevents thrombus formation in the rat with no effect on bleeding time at a higher dose.

Animals↗
PubMed1993

Characterization of the antiplasmin activity of human thrombospondin-1 in solution.

These studies demonstrate relatively rapid association of plasmin with thrombospondin and the effects of this interaction on plasmin activity towards D-Val-L-Leu-L-Lys p-nitroanilide hydrochloride (S-2251) and the proteinase inhibitors alpha 2-antiplasmin (alpha 2AP) and alpha 2-macroglobulin (alpha 2M). Binding of plasmin to thrombospondin reached an apparent reversible equilibrium within 3 min at 22 degrees C. The amidase activity of bound plasmin was inhibited. An analysis of S-2251 hydrolysis indicated that thrombospondin is a linear mixed-type plasmin inhibitor. The dissociation constant (KD) for the binding of plasmin to thrombospondin was 0.5 microM, assuming one plasmin binding site per thrombospondin homotrimer. Plasmin and miniplasmin slowly cleaved thrombospondin, yielding products which were comparable with those generated by other proteinases. Tranexamic acid inhibited the digestion of thrombospondin by plasmin and miniplasmin, suggesting an important role for the kringle-5 domain in this process. When plasmin was incubated first with thrombospondin and then with alpha 2AP, plasmin that was apparently bound to thrombospondin reacted with alpha 2AP at a decreased rate; however, within 20 min, all of the plasmin was recovered in complex with alpha 2AP. Similar results were obtained with alpha 2M. Transfer of plasmin from thrombospondin to alpha 2AP or alpha 2M probably required plasmin-thrombospondin-complex dissociation. A low level of reaction of alpha 2AP with thrombospondin-associated plasmin could not be ruled out. These results demonstrate that the activity of plasmin, when bound to thrombospondin, is greatly diminished or eliminated. The plasmin-thrombospondin complex, which is formed within 3 min, is fully reversible and the associated plasmin is in a latent form protected from proteinase inhibitors. Therefore, thrombospondin may regulate plasmin activity in a manner which is distinct from conventional proteinase inhibitors and other extracellular-matrix proteins.

Amidohydrolases↗