Increased release of tissue plasminogen activator and its inhibitor in human parotid saliva upon stimulation

Parotid saliva from 12 healthy volunteers was collected prior to and after 5 and 25 min of stimulation at a constant flow rate of 0.25 or 1.0 ml min^-1. In the salivary samples the concentrations of tPA (tissue-type plasminogen activator), PAI-1 (plasminogen activator inhibitor type-1), albumin and total protein were determined and the activity of amylase, tPA and PAI assessed. Presence of both tPA and PAI-1 antigen was demonstrated in all samples, and in unstimulated saliva the ratio between the activator and its inhibitor was 1:7. Upon stimulation we found a significantly increased concentration of PAI-1, a less pronounced increase in tPA concentration, unchanged amylase and total protein levels and significantly decreased albumin concentration. tPA activity was significantly reduced after prolonged stimulation which had no effect on PAI activity. In stimulated saliva a significant positive correlation between concentration of tPA and PAI-1 was demonstrated. Stimulation with citric acid had no effect on output of albumin which is passively filtered from blood, whereas the increase in flow rate corresponded to the significantly increased secretion rate of total protein and amylase which is secreted by gland cells. The secretion pattern of tPA and PAI-1 differed significantly from that of albumin in showing markedly increased output rate during the stimulation period, and the relative increase in output of PAI-1 was significantly higher than that of amylase and total protein. Thus, the results from this study suggest an active release of both tPA and its main inhibitor PAI-1 into saliva.     

Effect of thymoptin on hemostasis and fibrinolysis in rats with experimental nephritis

Immune nephritis in rats was induced by administration of nephrotoxic rabbit antiserum. The development of severe renal inflammation (proteinuria, edema, lipemia, increased erythrocyte sedimentation rate, and 30% mortality) was accompanied by hypercoagulation and inhibition of fibrinolysis. Repeated subcutaneous injections of thymoptin in a low dose of 0.1 μg/200 g (5 injections every other day) increased the severity of inflammation and prethrombotic state of the blood. Lengthening the period between injections (5 injections at 5-day intervals) was followed by a tendency toward attenuation of nephritis and correction of hypercoagulation. In healthy rats, thymoptin produced an opposite effect on hemostasis, which was manifested in moderate stimulation of fibrinolysis and hypocoagulation. Translated from Byulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 146, No. 7, pp. 8–12, July, 2008     

凝血酶激活的纤溶抑制物: 新的凝血纤溶调控因子

凝血酶激活的纤溶抑制物(Thrombin—activatable fibrinolysis inhibitor，简称TAFI)，作为凝血及纤溶调控因子，是近十年来国外医学界研究的热点之一；TAFI的基础研究是对经典凝血及纤溶调控机制的重要补充；在体内主要由凝血酶、凝血酶调节蛋白、纤溶酶、肝素、胰蛋白酶等物质激活而导致纤溶机制受抑，血栓溶解时间延长，从而增加血栓形成的危险性。TAFI在体内还参与缓激肽、补体等活性物质的调节。动物血栓模型运用TAFI拮抗剂与溶栓剂联合治疗，取得良好效果。国外医学界对TAFI与血液、心血管、内分泌等系统疾病的发病关系已展开广泛研究。     

Definition of major bleeding in clinical investigations of antihemostatic medicinal products in non-surgical patients

Summary. A variety of definitions of major bleeding have been used in published clinical studies, and this diversity adds to the difficulty in comparing data between trials and in performing meta-analyses. In the first step towards unified definitions of bleeding complications, the definition of major bleeding in non-surgical patients was discussed at the Control of Anticoagulation Subcommittee of the International Society on Thrombosis and Haemostasis. Arising from that discussion, a definition was developed that should be applicable to studies with all agents that interfere with hemostasis, including anticoagulants, platelet function inhibitors and fibrinolytic drugs. The definition and the text that follows have been reviewed and approved by the cochairs of the subcommittee and the revised version is published here. The intention is to also seek approval of this definition from the regulatory authorities.     

Functional approach to investigate Lp(a) in ischaemic heart and cerebral diseases

BACKGROUND: Lp(a), a major cardiovascular risk factor, contains a specific apolipoprotein, apo(a), which by virtue of structural homology with plasminogen inhibits the formation of plasmin, the fibrinolytic enzyme. A number of clinical reports support the role of Lp(a) as a cardiovascular or cerebral risk factor, and experimental data suggest that it may contribute to atherothrombosis by inhibiting fibrinolysis. DESIGN: A well-characterized model of a fibrin surface and an apo(a)-specific monoclonal antibody were used to develop a functional approach to detect pathogenic Lp(a). The assay is based on the competitive binding of Lp(a) and plasminogen for fibrin, and quantifies fibrin-bound Lp(a). High Lp(a) binding to fibrin is correlated with decreased plasmin formation. In a transversal case-control study we studied 248 individuals: 105 had a history of ischaemic cardiopathy (IC), 52 had cerebro-vascular disease (CVD) of thrombotic origin, and 91 were controls. RESULTS: The remarkably high apo(a) fibrin-binding in CVD (0.268 +/- 0.15 nmol L-1) compared with IC (0.155 +/- 0.12 nmol L-1) suggests the existence of peculiar and poorly understood differences in pro- or anti-thrombotic mechanisms in either cerebral and/or coronary arteries. CONCLUSIONS: Our results demonstrated that Lp(a) fibrin-binding and small Apo(a) isoforms are associated with athero-thrombotic disease.     

When Should Heparin Preferably Be Administered During Radiofrequency Catheter Ablation?

RF catheter ablation is complicated by thromboembolism in about 1% of patients. Limited knowledge exists concerning when and how to use anticoagulation or antithrombotic treatment. We studied the activation of coagulation (prothrombin fragment 1 + 2 [PF1 + 2] and D-dimer), platelets (beta-thromboglobulin [beta-TG]) and fibrinolysis (plasmin-antiplasmin complexes [PAP]) during RF ablation of accessory pathways in 30 patients. They were randomized to receive heparin (100 IU/kg, intravenously) (1) immediately after introduction of the femoral venous sheaths (group I) or (2) after the initial electrophysiological study, prior to the delivery of RF current (groups II and III). Group II additionally received saline irrigation of all femoral sheaths. After the initial bolus, 1,000 IU of heparin was supplied hourly in all groups. Within groups II and III, median plasma values of PF1 + 2 and beta-TG more than tripled (P < or = 0.007) during the diagnostic study and gradually declined during heparin administration despite RF current delivery. Median D-dimer tripled (P = 0.005) and PAP doubled (NS) before heparin administration; then both remained around the upper reference values. In the early heparin group, however, PF1 + 2, D-dimer, and PAP did not rise at all, and beta-TG showed only a slight increase towards the end of the procedure. The differences between group I versus groups II and III were statistically significant prior to the first RF current delivery (PF1 + 2, D-dimer, and beta-TG) and by the end of the procedure (PF1 + 2, D-dimer, and PAP). In conclusion, "late" heparin administration allows hemostatic activation during the initial catheterization and diagnostic study. By administering intravenous heparin immediately after introduction of the venous sheaths, hemostatic activation is significantly decreased. Saline irrigation of the venous sheaths added nothing to late heparin administration.     

Development of a new test for the global fibrinolytic capacity in whole blood.

BACKGROUND: The development of global tests for the fibrinolytic capacity in blood is hampered by the low base-line fibrinolytic activity in blood, by the involvement of both plasmatic components and blood cells in the fibrinolytic system and by the loss of fibrinolytic activity as a result of the action of plasminogen activator inhibitor-1 (PAI-1). OBJECTIVE: To develop a new test for the global fibrinolytic capacity (GFC) of whole blood samples. METHODS AND RESULTS: Collection of blood in thrombin increased the subsequent generation of fibrin degradation products. This was ascribed to rapid clot formation and concomitant reduction of in vitro neutralization of tissue-type plasminogen activator (tPA) by PAI-1. On the basis of this observation, the following test was designed: blood samples were collected in thrombin with and without aprotinin and clots were incubated for 3 h at 37 degrees C. The GFC was assessed from the difference between the fibrin degradation products in the two sera. The assay was applied to blood samples from patients and healthy subjects. Other hemostasis parameters were determined in plasma samples taken simultaneously. The GFC varied considerably (normal range 0.13-13.6 microg mL(-1)); physical exercise strongly increased the GFC. Statistically significant correlations were found with tPA activity, PAI-1 activity and fibrinogen level. A mixture of antibodies against tPA and urokinase-type plasminogen activator (uPA) completely inhibited the GFC. An inhibitor of activated thrombin-activatable fibrinolysis inhibitor (TAFI) accelerated fibrinolysis 8-fold. CONCLUSION: The new test represents a global assessment of the main fibrinolytic factors in plasma and potentially those associated with blood cells.