The EAHAD blood coagulation factor VII variant database.

Hereditary blood coagulation factor VII (FVII) deficiency is a rare autosomal recessive bleeding disorder resulting from variants in the gene encoding FVII (F7). Integration of genetic variation with functional consequences on protein function is essential for the interpretation of the pathogenicity of novel variants. Here, we describe the integration of previous locus-specific databases for F7 into a single curated database with enhanced features. The database provides access to in silico analyses that may be useful in the prediction of variant pathogenicity as well as cross-species sequence alignments, structural information, and functional and clinical severity described for each variant, where appropriate. The variant data is shared with the F7 Leiden Open Variation Database. The updated database now includes 221 unique variants, representing gene variants identified in 728 individuals. Single nucleotide variants are the most common type (88%) with missense representing 74% of these variants. A number of variants are found with relatively high minor allele frequencies that are not pathogenic but contribute significantly to the likely pathogenicity of coinherited variants due to their effect on FVII plasma levels. This comprehensive collection of curated information significantly aids the assessment of pathogenicity.

The European Association for Haemophilia and Allied Disorders (EAHAD) Coagulation Factor Variant Databases: Important resources for haemostasis clinicians and researchers.

INTRODUCTION: Advances in genomic sequencing have facilitated the sequencing of genes associated with disorders of haemostasis. The identification of variants within genes and access to curated data incorporating structural, functional, evolutionary as well as phenotypic data has become increasingly important in order to ascribe pathogenicity. AIM: The European Association for Haemophilia and Allied Disorders (EAHAD) Coagulation Factor Variant Database Project aims to provide a single port of entry to a web-accessible resource for variants in genes involved in clinical bleeding disorders. RESULTS: New databases have evolved from previously developed single gene variant coagulation database projects, incorporating new data, new analysis tools and a new common database architecture with new interfaces and filters. These new databases currently present information about the genotype, phenotype (laboratory and clinical) and structural and functional effects of variants described in the genes of factor (F) VII (F7), FVIII (F8), FIX (F9) and von Willebrand factor (VWF). CONCLUSION: The project has improved the quality and quantity of information available to the haemostasis research and clinical communities, thereby enabling accurate classification of disease severity in order to make assessments of likely pathogenicity.

Endogenous tissue plasminogen activator enhances fibrinolysis and limits thrombus formation in a clinical model of thrombosis.

OBJECTIVE: Using a clinical model of deep arterial injury, we assessed the ability of exogenous and endogenous tissue plasminogen activator (t-PA) to limit acute in situ thrombus formation. APPROACH AND RESULTS: Ex vivo thrombus formation was assessed in the Badimon chamber at low and high shear rates in 2 double-blind randomized cross-over studies of 20 healthy volunteers during extracorporeal administration of recombinant t-PA (0, 40, 200, and 1000 ng/mL) or during endogenous t-PA release stimulated by intra-arterial bradykinin infusion in the presence or absence of oral enalapril. Recombinant t-PA caused a dose-dependent reduction in thrombus area under low and high shear conditions (P<0.001 for all). Intra-arterial bradykinin increased plasma t-PA concentrations in the chamber effluent (P<0.01 for all versus saline) that was quadrupled in the presence of enalapril (P<0.0001 versus placebo). These increases were accompanied by an increase in plasma D-dimer concentration (P<0.005 for all versus saline) and, in the presence of enalapril, a reduction in thrombus area in the low shear (16±5; P=0.03) and a trend toward a reduction in the high shear chamber (13±7%; P=0.07). CONCLUSIONS: Using a well-characterized clinical model of coronary arterial injury, we demonstrate that endogenous t-PA released from the vascular endothelium enhances fibrinolysis and limits in situ thrombus propagation. These data support a crucial role for the endogenous fibrinolytic system in vivo and suggest that continued exploration and manipulation of its therapeutic potential are warranted.

Microparticles, malignancy and thrombosis.

Microparticles (MPs) are considered to be important biological effectors of several different physiological and pathological processes. There is increasing evidence of their role in haemostasis and thrombosis, and also of their importance in cancer cell survival, invasiveness and metastasis. The level of circulating MPs has been assessed in many different disease states, and there are reports that patients with malignancy and patients with thrombosis have increased levels of circulating MPs and MP-dependent thrombogenic potential. Research into the function and effect of MPs is currently hampered by a lack of standardization in the methods used to identify and quantify them. As these methods improve it is likely that MP assays will be of use both diagnostically and therapeutically in the future.

Effects of acute insulin-induced hypoglycemia on indices of inflammation: putative mechanism for aggravating vascular disease in diabetes.

OBJECTIVE: To examine the effects of acute insulin-induced hypoglycemia on inflammation, endothelial dysfunction, and platelet activation in adults with and without type 1 diabetes. RESEARCH DESIGN AND METHODS: We studied 16 nondiabetic adults and 16 subjects with type 1 diabetes during euglycemia (blood glucose 4.5 mmol/l) and hypoglycemia (blood glucose 2.5 mmol/l). Markers of inflammation, thrombosis, and endothelial dysfunction (soluble P-selectin, interleukin-6, von Willebrand factor [vWF], tissue plasminogen activator [tPA], high-sensitivity C-reactive protein [hsCRP], and soluble CD40 ligand [sCD40L]) were measured; platelet-monocyte aggregation and CD40 expression on monocytes were determined using flow cytometry. RESULTS: In nondiabetic participants, platelet activation occurred after hypoglycemia, with increments in platelet-monocyte aggregation and P-selectin (P

Vascular dysfunction in chronic obstructive pulmonary disease.

RATIONALE: Cardiovascular disease is a major cause of morbidity and mortality in patients with chronic obstructive pulmonary disease (COPD), which may in part be attributable to abnormalities of systemic vascular function. It is unclear whether such associations relate to the presence of COPD or prior smoking habit. OBJECTIVES: To undertake a comprehensive assessment of vascular function in patients with COPD and healthy control subjects matched for smoking history. METHODS: Eighteen men with COPD were compared with 17 healthy male control subjects matched for age and lifetime cigarette smoke exposure. Participants were free from clinically evident cardiovascular disease. MEASUREMENTS AND MAIN RESULTS: Pulse wave velocity and pulse wave analysis were measured via applanation tonometry at carotid, radial, and femoral arteries. Blood flow was measured in both forearms using venous occlusion plethysmography during intrabrachial infusion of endothelium-dependent vasodilators (bradykinin, 100-1,000 pmol/min; acetylcholine, 5-20 microg/min) and endothelium-independent vasodilators (sodium nitroprusside, 2-8 microg/min; verapamil, 10-100 microg/min). Tissue plasminogen activator (t-PA) was measured in venous plasma before and during bradykinin infusions. Patients with COPD have greater arterial stiffness (pulse wave velocity, 11 +/- 2 vs. 9 +/- 2 m/s; P = 0.003; augmentation index, 27 +/- 10 vs. 21 +/- 6%; P = 0.028), but there were no differences in endothelium-dependent and -independent vasomotor function or bradykinin-induced endothelial t-PA release (P > 0.05 for all). CONCLUSIONS: COPD is associated with increased arterial stiffness independent of cigarette smoke exposure. However, this abnormality is not explained by systemic endothelial dysfunction. Increased arterial stiffness may represent the mechanistic link between COPD and the increased risk for cardiovascular disease associated with this condition.

An update on the assessment and management of the risk of transmission of variant Creutzfeldt-Jakob disease by blood and plasma products.

There have been four highly probable instances of variant Creutzfeldt-Jakob disease (vCJD) transmission by non-leucocyte depleted red cell concentrates and it is now clear that the infectious agent is transmissible by blood components. To date there in no reported evidence that the infectious agent has been transmitted by fractionated plasma products, e.g. factor VIII concentrate. This review outlines current and potential risk management strategies including donor deferral criteria, the potential for donor screening, blood component processing and prion reduction filters, plasma product manufacture and the difficulties in identification and notification of those considered 'at risk of vCJD for public health purposes'.

Vascular B1 kinin receptors in patients with congestive heart failure.

Animal models suggest a vasomotor role for the B1 kinin receptor in cardiovascular disease states. In patients with heart failure treated with angiotensin-converting enzyme inhibition (ACEi), or combined B1/B2 receptor antagonism, but not B2 receptor antagonism alone, causes vasoconstriction. However, B1 agonism has no effect on vasomotor or fibrinolytic function. Findings from transgenic animals lacking the B2 receptor suggest that these conflicting data may be explained by cross-talk between B1 and B2 receptors. We hypothesized that B1 stimulation causes vasodilatation and tissue plasminogen activator release in the human forearm when B2 receptor signaling is inhibited. Forearm blood flow was measured in 16 patients with heart failure receiving ACEi. In double-blinded crossover studies, intrabrachial Lys-[Leu8]-des-Arg9-bradykinin (B1 antagonist), lys-des-Arg9-bradykinin (B1 agonist), bradykinin (B2 agonist), and sodium nitroprusside (endothelium-independent vasodilator) were infused alone or with HOE-140 (B2 antagonist). HOE-140 did not affect basal vascular tone or t-PA release, but it abolished bradykinin-induced vasodilatation and t-PA release (P < 0.0001). Blood flow and t-PA release were unaffected by B1 agonism or antagonism in the presence and absence HOE-140. Our findings do not support a role for crosstalk between the B1 and B2 kinin receptors in the human peripheral circulation.

Marked impairment of protease-activated receptor type 1-mediated vasodilation and fibrinolysis in cigarette smokers: smoking, thrombin, and vascular responses in vivo.

OBJECTIVES: We sought to test the hypothesis that cigarette smoking adversely alters protease-activated receptor type 1 (PAR-1)-mediated vascular effects in vivo in humans. BACKGROUND: Distinct from its role in the coagulation cascade, thrombin exerts its major cellular and cardiovascular actions via PAR-1. The activation of PAR-1 causes endothelium-dependent arterial vasodilation and the release of endogenous fibrinolytic factors. METHODS: Forearm blood flow was measured with venous occlusion plethysmography in 12 cigarette smokers and 12 age- and gender-matched nonsmokers during intrabrachial infusions of PAR-1-activating-peptide (SFLLRN; 5 to 50 nmol/min), bradykinin (100 to 1,000 pmol/min), and sodium nitroprusside (2 to 8 mug/min). Plasma tissue plasminogen activator (t-PA) and plasminogen-activator inhibitor 1 antigen and activity concentrations were measured throughout the experiment. RESULTS: All agonists caused dose-dependent increases in forearm blood flow (p < 0.0001 for all). Although bradykinin and sodium nitroprusside caused similar vasodilation, SFLLRN-induced vasodilation was attenuated in smokers (p = 0.04). Smokers had modest reductions in bradykinin-induced active t-PA release (reduced by 37%, p = 0.03) and had a marked impairment of SFLLRN-induced t-PA antigen (p = 0.02) and activity (p = 0.006) release, with a 96% reduction in overall net t-PA antigen release. The use of SFLLRN also caused similar (p = NS) increases in inactive plasminogen-activator inhibitor 1 in both smokers and nonsmokers (p

Role of the endothelium in the vascular effects of the thrombin receptor (protease-activated receptor type 1) in humans.

OBJECTIVES: The purpose of this study was to determine the role of the endothelium in the vascular actions of protease-activated receptor type 1 (PAR-1) activation in vivo in man. BACKGROUND: Thrombin is central to the pathophysiology of atherothrombosis. Its cellular actions are mediated via PAR-1. Protease-activated receptor type 1 activation causes arterial vasodilation, venoconstriction, platelet activation, and tissue-type plasminogen activator release in man. METHODS: Dorsal hand vein diameter was measured in 6 healthy volunteers before and after endothelial denudation. Forearm arterial blood flow, plasma fibrinolytic factors, and platelet activation were measured in 24 healthy volunteers during venous occlusion plethysmography. The effects of inhibition of prostacyclin, nitric oxide (NO), and endothelium-derived hyperpolarizing factor on PAR-1 responses were assessed during coadministration of aspirin, the "NO clamp" (L-N(G)-monomethyl arginine and sodium nitroprusside), and tetraethylammonium ion, respectively. RESULTS: Endothelial denudation did not affect PAR-1-evoked venoconstriction (SFLLRN; 0.05 to 15 nmol/min). Although aspirin had no effect, SFLLRN-induced vasodilation (5 to 50 nmol/min) was attenuated by the NO clamp (p < 0.0001) and tetraethylammonium ion (p < 0.05) and abolished by their combination (p < 0.01). The NO clamp augmented SFLLRN-induced tissue-type plasminogen activator and plasminogen activator inhibitor type 1 antigen (p < 0.0001) release, but tetraethylammonium ion and aspirin had no effect. SFLLRN-induced platelet activation was unaffected by NO or prostacyclin inhibition. CONCLUSIONS: Acting via PAR-1, thrombin causes contrasting effects in the human vasculature and has a major interaction with the endothelium. This highlights the critical importance of endothelial function during acute arterial injury and intravascular thrombosis, as occurs in cardiovascular events including myocardial infarction and stroke.

Endothelial fibrinolytic capacity predicts future adverse cardiovascular events in patients with coronary heart disease.

OBJECTIVE: The endothelium-derived fibrinolytic factor tissue plasminogen activator (t-PA) is a major determinant of vessel patency after coronary plaque rupture and thrombosis. We assessed whether endothelial fibrinolytic capacity predicts atherothrombotic events in patients with coronary heart disease. METHODS AND RESULTS: Plasma t-PA and plasminogen activator inhibitor (PAI)-1 concentrations were measured during intrabrachial substance P infusion in 98 patients with angiographically proven stable coronary heart disease. Forearm blood flow was measured during infusion of substance P and sodium nitroprusside. Cardiovascular events (cardiovascular death, myocardial infarction [MI], ischemic stroke [CVA], and emergency hospitalization for unstable angina) were determined during 42 months of follow-up. Patients experiencing a cardiovascular event (n=19) had similar baseline characteristics to those free of events. Substance P caused a dose-dependent increase in plasma t-PA concentrations (P<0.001). However, net t-PA release was 72% lower in the patients who experienced death, MI, or CVA, and 48% lower in those who suffered death, MI, CVA or hospitalization for unstable angina (P<0.05). Major adverse cardiovascular events were most frequent in those with the lowest fibrinolytic capacity (P=0.03 for trend); patients with the lowest quartile of t-PA release had the highest rate of adverse events (P=0.01). CONCLUSION: Endothelial fibrinolytic capacity, as measured by stimulated t-PA release, predicts the future risk of adverse cardiovascular events in patients with coronary heart disease. We suggest that endothelial fibrinolytic capacity is a powerful novel determinant of cardiovascular risk.

Mortality rates, life expectancy, and causes of death in people with hemophilia A or B in the United Kingdom who were not infected with HIV.

Since the 1970s, mortality in the hemophilia population has been dominated by human immunodeficiency virus (HIV) and few reports have described mortality in uninfected individuals. This study presents mortality in 6018 people with hemophilia A or B in the United Kingdom during 1977 to 1998 who were not infected with HIV, with follow-up until January 1, 2000. Given disease severity and factor inhibitor status, all-cause mortality did not differ significantly between hemophilia A and hemophilia B. In severe hemophilia, all-cause mortality did not change significantly during 1977 to 1999. During this period, it exceeded mortality in the general population by a factor of 2.69 (95% confidence interval [CI]: 2.37-3.05), and median life expectancy in severe hemophilia was 63 years. In moderate/mild hemophilia, all-cause mortality did not change significantly during 1985 to 1999, and median life expectancy was 75 years. Compared with mortality in the general population, mortality from bleeding and its consequences, and from liver diseases and Hodgkin disease, was increased, but for ischemic heart disease it was lower, at only 62% (95% CI: 51%-76%) of general population rates, and for 14 other specific causes it did not differ significantly from general population rates. There was no evidence of any death from variant Creutzfeldt-Jakob disease or from conditions that could be confused with it.

Plasma microparticles and vascular disorders.

Microparticles are circulating, phospholipid rich, submicron particles released from the membranes of endothelial cells, platelets, leucocytes and erythrocytes. Investigation into their biological activity has revealed diverse actions in coagulation, cell signalling and cellular interactions. These actions are mediated through their phospholipid rich surfaces and the expression of cell surface molecules which reflect their cell of origin and its state of activation. Microparticle numbers are reported to be elevated in a number of conditions where vascular dysfunction and inflammation are important pathophysiological mechanisms, for example coronary artery disease or thrombotic microangiopathies. Currently, there are a variety of different methods used for the quantitation of circulating microparticles; however with standardisation their assessment may prove to be of clinical value, reflecting the state of the vasculature. Knowledge of the functional properties of microparticles will contribute to our understanding of the mechanisms underlying vascular dysfunction and prothrombotic states.

Direct vascular effects of protease-activated receptor type 1 agonism in vivo in humans.

BACKGROUND: Protease-activated receptor type 1 (PAR-1) has been proposed as the principal thrombin receptor in humans, although its actions in vivo have not been defined. The aim of the present study was to determine the direct vascular actions of PAR-1 agonism in humans. METHODS AND RESULTS: Dorsal hand vein diameter was measured by the Aellig technique in 14 healthy volunteers during local intravenous SFLLRN (PAR-1 agonist; 0.05 to 15 nmol/min) and SLIGKV (PAR-2 agonist; 1.6 to 160 nmol/min) infusions. The venous effects of SFLLRN were further assessed in the presence or absence of norepinephrine or the glycoprotein IIb/IIIa antagonist tirofiban. Forearm blood flow was measured by venous occlusion plethysmography in 16 volunteers during infusion of SFLLRN (1 to 50 nmol/min), SLIGKV (160 to 800 nmol/min), and the endothelium-dependent vasodilator bradykinin (100 to 1000 pmol/min). Platelet-monocyte binding (a sensitive measure of platelet activation) and plasma tissue plasminogen activator (tPA), plasminogen-activator inhibitor 1, and von Willebrand factor concentrations were measured at intervals throughout the study. SFLLRN caused dose-dependent venoconstriction (P<0.001) that was unaffected by norepinephrine or tirofiban co-infusion. In forearm resistance vessels, SFLLRN increased forearm blood flow (P<0.001), tPA release (P<0.001), and platelet-monocyte binding (P<0.0001) without affecting plasma plasminogen-activator inhibitor 1 or von Willebrand factor concentrations. SLIGKV caused venous (P<0.001) and arterial (P<0.01) dilatation without tPA release. CONCLUSIONS: We have demonstrated that PAR-1 agonism causes platelet activation, venous constriction, arterial dilatation, and tPA release in vivo in humans. These unique and contrasting effects provide important insights into the physiological and pathophysiological role of thrombin in the human venous and arterial circulations.

Clinical perspectives of emerging pathogens in bleeding disorders.

As a result of immunological and nucleic-acid screening of plasma donations for transfusion-transmissible viruses, and the incorporation of viral reduction processes during plasma fractionation, coagulation-factor concentrates (CFC) are now judged safe in terms of many known infectious agents, including hepatitis B and C viruses, HIV, and human T-cell lymphotropic virus. However, emerging pathogens could pose future threats, particularly those with blood-borne stages that are resistant to viral-inactivation steps in the manufacturing process, such as non-lipid-coated viruses. As outlined in this Review, better understanding of infectious diseases allows challenges from newly described agents of potential concern in the future to be anticipated, but the processes of zoonotic transmission and genetic selection or modification ensure that plasma-derived products will continue to be subject to infectious concerns. Manufacturers of plasma-derived CFC have addressed the issue of emerging infectious agents by developing recombinant products that limit the need for human plasma during production. Such recombinant products have extended the safety profile of their predecessors by ensuring that all reagents used for cell culture, purification steps, and stabilisation and storage buffers are completely independent of human plasma.

Plasma TAFI and soluble CD40 ligand do not predict reperfusion following thrombolysis for acute myocardial infarction.

INTRODUCTION: Thrombolytic therapy fails to achieve reperfusion in almost a third of patients with acute myocardial infarction. Thrombin activatable fibrinolysis inhibitor (TAFI) and soluble CD40 ligand (sCD40L) are novel endogenous fibrinolytic and atherothrombotic factors that determine clot stability. We investigated whether admission plasma thrombin activatable fibrinolysis inhibitor (TAFI) and soluble CD40 ligand (sCD40L) concentrations predicted reperfusion following thrombolytic therapy in patients with acute myocardial infarction. MATERIALS AND METHODS: Prior to administration of thrombolytic therapy, venous blood was collected from 110 patients presenting with acute ST segment elevation myocardial infarction and plasma assayed for tissue plasminogen activator (t-PA) antigen and activity, plasminogen activator inhibitor type-1 antigen (PAI-1), TAFI antigen and activity, C-reactive protein (CRP) and sCD40L concentrations. Reperfusion was determined using continuous ST segment monitoring. RESULTS: Reperfusion occurred in 77 (70%) patients with a mean treatment to reperfusion time of 83 +/- 46 min. Peak creatine kinase was significantly lower in patients who reperfused (1578 +/- 1199 versus 2200 +/- 1744 U/L; P < 0.05) and correlated with time to reperfusion (r = 0.44 [95% CI: 0.23 - 0.61], P = 0.0001). There was a modest correlation between plasma TAFI antigen and activity (r = 0.3 [95% CI: 0.04 - 0.53]; P < 0.05). There were no significant associations between coronary reperfusion and plasma concentrations of t-PA, PAI-1, TAFI, CRP or sCD40L. CONCLUSIONS: Systemic plasma TAFI, sCD40L and CRP concentrations do not predict reperfusion in patients receiving thrombolytic therapy for acute ST elevation myocardial infarction.

Managing the risk of transmission of variant Creutzfeldt Jakob disease by blood products.

Whereas plasma-derived clotting factor concentrates now have a very good safety record for not being infectious for lipid enveloped viruses, concern has arisen about the possibility that prion diseases might be transmitted by blood products. There is epidemiological evidence that classical sporadic Creutzfeld Jakob disease (CJD) is not transmitted by blood transfusion. There is now good evidence that the abnormal prion associated with variant CJD can be transmitted by transfusion of fresh blood components and infect recipients. To reduce the risk of the pathological prion in the UK infecting recipients of clotting factor concentrates, these are now only manufactured from imported plasma collected from countries where there has not been bovine spongiform encephalopathy (BSE) in cattle and the risk of variant CJD in the population is, therefore, considered negligible. The safety of these concentrates is also enhanced because prion protein is, to an appreciable extent, excluded by the manufacturing process from the final product. To help reduce the chance of prion transmission by fresh blood products, donations are leucodepleted, there is increasing use of imported fresh frozen plasma (especially for treating children) and potential donors, who have been recipients of blood since 1980 (the beginning of the BSE epidemic in cattle) are deferred.

Vascular and fibrinolytic effects of intra-arterial tumour necrosis factor-alpha in patients with coronary heart disease.

Elevated plasma t-PA (tissue plasminogen activator) and serum CRP (C-reactive protein) concentrations are associated with an adverse cardiovascular risk. In the present study, we investigated whether acute local inflammation causes vascular dysfunction and influences t-PA release in patients with stable coronary heart disease. Serum CRP, plasma t-PA and PAI-1 (plasminogen activator inhibitor type 1) concentrations were determined in 95 patients with stable coronary heart disease. A representative subpopulation of 12 male patients received an intra-brachial infusion of TNF-alpha (tumour necrosis factor-alpha) and saline placebo using a randomized double-blind cross-over study design. Forearm blood flow and plasma fibrinolytic and inflammatory variables were measured. Serum CRP concentrations correlated with plasma t-PA concentrations (r=0.37, P<0.001) and t-PA/PAI-1 ratio (r=-0.21, P<0.05). Intra-arterial TNF-alpha caused a rise in t-PA concentrations (P<0.001) without affecting blood flow or PAI-1 concentrations. TNF-alpha pretreatment impaired acetylcholine- and sodium nitroprusside-induced vasodilatation (P<0.001 for both) whilst doubling bradykinin-induced t-PA release (P=0.006). In patients with stable coronary heart disease, plasma fibrinolytic factors correlate with a systemic inflammatory marker and local vascular inflammation directly impairs vasomotor function whilst enhancing endothelial t-PA release. We suggest that the adverse prognosis associated with elevated plasma t-PA concentrations relates to the underlying causative association with vascular inflammation and injury.

B1 kinin receptor does not contribute to vascular tone or tissue plasminogen activator release in the peripheral circulation of patients with heart failure.

OBJECTIVE: Vascular expression of the B1 kinin receptor is markedly upregulated with left ventricular dysfunction and angiotensin-converting enzyme (ACE) inhibition, but its function remains unclear. Inhibitors of ACE potentiate bradykinin-mediated B2 receptor-dependent vasodilatation and tissue plasminogen activator (tissue-type plasminogen activator [t-PA]) release. We investigated the contribution of the B1 receptor to the maintenance of vascular tone and t-PA release in patients with heart failure. METHODS AND RESULTS: Eleven patients were treated with enalapril (10 mg twice daily) or losartan (50 mg twice daily) in a randomized double-blind crossover trial. During week 6 of each treatment, patients received an intrabrachial infusion of Lys-des-Arg9-bradykinin (B1 agonist; 1 to 10 nmol/min), bradykinin (30 to 300 pmol/min), Lys-[Leu8]-des-Arg9-bradykinin (B1 antagonist; 1 to 10 nmol/min), and norepinephrine (60 to 540 pmol/min). Blood flow and t-PA release were measured using venous occlusion plethysmography and blood sampling. Bradykinin (P<0.001 for all), but not Lys-des-Arg9-bradykinin, caused vasodilatation and t-PA antigen and activity release. Norepinephrine (P<0.001), but not Lys-[Leu8]-des-Arg9-bradykinin, caused vasoconstriction. Compared with losartan, enalapril augmented bradykinin-mediated vasodilatation (P<0.05) and t-PA release (P<0.01 for all) but had no effect on B(1) receptor-mediated responses. CONCLUSIONS: The B1 kinin receptor does not have a major vasomotor or fibrinolytic role in patients with heart failure. Augmentation of kinin-mediated vasodilatation and t-PA release by ACE inhibition is restricted to the B2 receptor.