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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.

Objective: Pregnancy is associated with marked changes in vascular physiology and an increased risk of thrombosis. The aim of the study was to assess the effect of pregnancy on the acute release of tissue plasminogen activator (t-PA) from the endothelium., Methods and Results: Ten primigravida pregnant women were recruited in the third trimester of pregnancy (week 36 +/- 1) and compared with 20 age-matched non-pregnant women (day 9.8 +/- 0.3 of menstrual cycle). Blood flow and plasma fibrinolytic factors were measured in both forearms by venous occlusion plethysmography and blood sampling, respectively, during unilateral brachial artery infusions of bradykinin (100-1000 pmol min(-1)). Pregnant women had higher plasma plasminogen activator inhibitor type 1 (PAI-1) antigen concentrations (77.1 +/- 12.4 vs. 21.5 +/- 9.8 ng mL(-1); P = 0.004) that resulted in lower basal t-PA/PAI-1 ratios (0.2 +/- 0.1 vs. 0.6 +/- 0.1; P = 0.02) and plasma t-PA activity concentrations (0.17 +/- 0.02 vs. 0.58 +/- 0.06 IU mL(-1); P < 0.0004). In both groups, bradykinin caused dose-dependent increases in blood flow and local release of plasma t-PA antigen and activity (P < 0.005 for all). Both the plasma t-PA/PAI-1 ratios and the net release of active t-PA were markedly reduced in pregnant women (P < 0.05 for both). Area under the curve for net active t-PA release was reduced by 36%., Conclusions: Pregnancy is associated with major perturbations of endogenous fibrinolytic capacity with an overwhelming increase in plasma PAI-1 concentrations and an inadequate release of active t-PA. These prothrombotic effects may, in part, explain the increased risk of arterial and venous thrombosis in pregnant women.

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

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.

Objectives: To determine if polymorphisms of the tissue plasminogen activator (t-PA) gene influence acute endogenous t-PA release in patients with coronary heart disease (CHD)., Methods: Forearm blood flow and plasma t-PA concentrations were measured in response to intra-brachial infusion of substance P and sodium nitroprusside in 96 patients with stable CHD. Genotyping was performed using a Taqman polymerase chain reaction assay specifically designed to detect the polymorphisms of interest: (i) Alu-repeat insertion/deletion sequence; (ii) C-->T substitution in an upstream enhancer region (-7351 C/T); (iii) T-->C in exon 6 (20 099 T/C); and (iv) T-->A (27 445 T/A) in intron 10., Results: Substance P and sodium nitroprusside caused dose-dependent increases in forearm blood flow in all patients (P < 0.001 for all) that were independent of the four genetic polymorphisms. Similarly, there were no differences in basal plasma t-PA antigen concentrations or net t-PA release between genotypes. Compared to non-smokers, smokers exhibited impaired substance P-induced vasodilatation (P < 0.001) and t-PA release (P = 0.05)., Conclusions: Despite confirming our previous findings in cigarette smokers, we have found no effect of polymorphisms of the t-PA gene on two complementary aspects of endothelial function. We conclude that genetic variation of the t-PA locus is unlikely to have a major influence on acute t-PA release in subjects with established CHD.

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.

Objective: We sought to assess pharmacodynamic responses to the bradykinin antagonist B9340 and to determine the contribution of the endothelial bradykinin receptor to stimulated tissue plasminogen activator (t-PA) release in humans., Methods and Results: Bilateral forearm blood flow and plasma fibrinolytic variables were measured in 8 volunteers during 100 minutes of intrabrachial infusions of saline placebo, B9340 at 4.5 nmol/min, or B9340 at 13.5 nmol/min. On each occasion, intra-arterial bradykinin (30 to 3000 pmol/min) and substance P (4 to 16 pmol/min) were coinfused for 10 minutes at each dose. To assess the onset and offset of action, 6 additional subjects on 2 occasions received intra-arterial bradykinin (100 pmol/min) for 60 minutes with a coinfusion of either saline placebo or B9340 (13.5 nmol/min) for 12 minutes. During placebo infusion, bradykinin and substance P caused dose-dependent vasodilatation in the infused forearm (P<0.001). B9340 caused a dose-dependent inhibition of bradykinin-induced forearm vasodilatation and t-PA release (P<0.001) without affecting substance P-induced vasodilatation or t-PA release (P=NS). B9340 caused a reversible inhibition of bradykinin-induced vasodilatation (P<0.001) with a rapid onset and offset of action., Conclusions: B9340 is a potent, reversible, and selective competitive receptor antagonist of bradykinin-induced vasodilatation and t-PA release in humans.

Objective: Inflammation contributes to the pathogenesis of cardiovascular disease, potentially through the actions of proinflammatory cytokines. We assessed the direct effects of local intra-arterial tumor necrosis factor-alpha (TNF-alpha), interleukin-6, and endotoxin on blood flow and endogenous tissue plasminogen activator (t-PA) release in vivo in humans., Methods and Results: In a double-blind, randomized, placebo-controlled trial, blood flow, plasma cytokine, and fibrinolytic parameters were measured using venous occlusion plethysmography and blood sampling. Ten subjects received intrabrachial TNF-alpha, interleukin-6, and endotoxin infusions, and 8 additional subjects received intrabrachial infusions of bradykinin, acetylcholine, and sodium nitroprusside after pretreatment with TNF-alpha. TNF-alpha but not interleukin-6, endotoxin, or placebo caused a gradual and sustained approximately 20-fold increase in plasma t-PA concentrations (P<0.001) that was associated with elevated plasma interleukin-6 concentrations (P<0.05) but without an effect on blood flow or plasminogen activator inhibitor type 1 antigen. Compared with placebo, TNF-alpha pretreatment impaired bradykinin- and acetylcholine-induced vasodilatation (P<0.03) and resulted in a doubling of bradykinin-induced t-PA release (P<0.05)., Conclusions: Intra-arterial TNF-alpha causes an acute local vascular inflammation that is associated with impaired endothelium-dependent vasomotion as well as a sustained and substantial increase in endothelial t-PA release. TNF-alpha has potentially both adverse vasomotor and beneficial profibrinolytic effects on endothelial function.

Objectives: The purpose of this study was to investigate in vivo the effects of acute systemic inflammation on the endogenous fibrinolytic capacity in men., Background: Systemic inflammation and endogenous fibrinolysis play a major role in the pathogenesis of coronary artery disease. Although previous studies have shown impaired endothelium-dependent vasomotor function, the effects of inflammation on the endothelial release of the fibrinolytic factor tissue plasminogen activator (t-PA) are unknown., Methods: In a double-blind randomized placebo-controlled crossover trial, we administered a mild inflammatory stimulus, Salmonella typhi vaccine, or saline placebo to eight healthy men on two separate occasions. Six hours after vaccination, blood flow and plasma fibrinolytic variables were measured in both arms during intrabrachial infusions of bradykinin (40 to 1,000 pmol/min), acetylcholine (5 to 20 microg/min), and sodium nitroprusside (2 to 8 microg/min)., Results: Compared with placebo, the S. typhi vaccination caused a rise in white cell count (11.1 +/- 0.5 x10(9)/l vs. 7.9 +/- 0.8 x10(9)/l; p = 0.004) and plasma interleukin-6 concentrations (6.9 +/- 1.4 pg/ml vs. 1.6 +/- 0.4 pg/ml; p = 0.01) in addition to a significant augmentation of t-PA antigen (45 +/- 9 ng/100 ml/min at peak dose vs. 24 +/- 8 ng/100 ml/min at peak dose; p = 0.016, analysis of variance) and activity (104 +/- 15 IU/100 ml/min vs. 54 +/- 12 IU/100 ml/min; p = 0.006, analysis of variance) release during bradykinin infusion. Forearm blood flow increased in a dose-dependent manner after bradykinin, acetylcholine and sodium nitroprusside infusions (p < 0.001), but this was unaffected by vaccination., Conclusions: Our results showed that acute systemic inflammation augmented local forearm t-PA release in men, which suggests that acute inflammation may invoke a protective response by enhancing the acute endogenous fibrinolytic capacity in healthy men. Further studies are needed to clarify whether this response is impaired in patients with cardiovascular disease.

Objectives: The aim of the present study was to assess the contribution of angiotensin-converting enzyme (ACE) inhibitor therapy to bradykinin-induced tissue-type plasminogen activator (t-PA) release in patients with heart failure (HF) secondary to ischemic heart disease., Background: Bradykinin is a potent endothelial cell stimulant that causes vasodilatation and t-PA release. In large-scale clinical trials, ACE inhibitor therapy prevents ischemic events., Methods: Nine patients with symptomatic HF were evaluated on two occasions: during and following seven-day withdrawal of long-term ACE inhibitor therapy. Forearm blood flow was measured using bilateral venous occlusion plethysmography. Intrabrachial bradykinin (30 to 300 pmol/min), substance P (2 to 8 pmol/min), and sodium nitroprusside (1 to 4 pmol/min) were infused, and venous blood samples were withdrawn from both forearms for estimation of fibrinolytic variables., Results: On both study days, bradykinin and substance P caused dose-dependent vasodilatation and release of t-PA from the infused forearm (p < 0.05 by analysis of variance [ANOVA]). Long-term ACE inhibitor therapy caused an increase in forearm vasodilatation (p < 0.05 by ANOVA) and t-PA release (p < 0.001 by ANOVA) during bradykinin, but not substance P, infusion. Maximal local plasma t-PA activity concentrations approached 100 IU/ml, and maximal forearm protein release was approximately 4.5 microg/min., Conclusions: Long-term ACE inhibitor therapy augments bradykinin-induced peripheral vasodilatation and local t-PA release in patients with HF due to ischemic heart disease. Local plasma t-PA activity concentrations approached those seen during systemic thrombolytic therapy for acute myocardial infarction. This may contribute to the primary mechanism of the anti-ischemic effects associated with long-term ACE inhibitor therapy.

Objective: To assess acute tissue plasminogen activator (t-PA) release in vivo in patients with hypercholesterolaemia in the presence and absence of lipid lowering treatment and in matched normocholesterolaemic controls., Design: Parallel group comparison and double blind randomised crossover., Setting: University hospital., Patients: Eight patients with hypercholesterolaemia (> 7.8 mmol/l) and eight matched normocholesterolaemic controls (< 5.5 mmol/l)., Methods: Blood flow and plasma fibrinolytic factors were measured in both forearms during unilateral brachial artery infusions of the endothelium dependent vasodilator substance P (2-8 pmol/min) and the endothelium independent vasodilator sodium nitroprusside (1-4 microg/min)., Interventions: In patients, measurements were made on three occasions: at baseline and after six weeks of placebo or pravastatin 40 mg daily administered in a double blind randomised crossover design., Main Outcome Measures: Acute release of t-PA., Results: Compared with patients, in normocholesterolaemic control subjects substance P caused greater dose dependent increases in forearm blood flow (p < 0.05) but similar increases in plasma t-PA antigen and activity concentrations. During pravastatin treatment in patients, total serum cholesterol fell by 22% from a mean (SEM) of 8.1 (0.3) to 6.4 (0.4) mmol/l (p = 0.002) and substance P induced vasodilatation was no longer significantly impaired in comparison with controls. However, despite reproducible responses, pravastatin treatment was not associated with significant changes in basal or substance P induced t-PA release., Conclusions: Hypercholesterolaemia and lipid lowering treatment cause no demonstrable effects on acute substance P induced t-PA release in vivo. This suggests that the preventative benefits of lipid lowering treatment are unlikely to be mediated by improvements in endogenous fibrinolysis.

Background: The aim of the study was to establish the influence of proximal coronary artery atheroma and smoking habit on the stimulated release of tissue plasminogen activator (tPA) from the heart., Methods and Results: After diagnostic coronary angiography in 25 patients, the left anterior descending coronary artery (LAD) was instrumented, and the proximal LAD plaque volume was determined by use of intravascular ultrasound (IVUS). Blood flow and fibrinolytic responses to selective LAD infusion of saline, substance P (10 to 40 pmol/min; endothelium-dependent), and sodium nitroprusside (5 to 20 microgram/min; endothelium-independent) were measured by intracoronary IVUS and Doppler, combined with arterial and coronary sinus blood sampling. Mean plaque burden was 5.5+/-0.8 mm(3)/mm vessel (range 0.6 to 13.7 mm(3)/mm vessel). LAD blood flow increased with both substance P and sodium nitroprusside (P<0.001), although coronary sinus plasma tPA antigen and activity concentrations increased only during substance P infusion (P<0.006 for both). There was a strong inverse correlation between the LAD plaque burden and release of active tPA (r=-0.61, P=0.003). Cigarette smoking was associated with impaired coronary release of active tPA (current smokers, 31+/-23 IU/min; ex-smokers, 50+/-33 IU/min; nonsmokers 202+/-73 IU/min; P<0.05)., Conclusions: We found that both the coronary atheromatous plaque burden and smoking habit are associated with a reduced acute local fibrinolytic capacity of the heart. These important findings provide evidence of a direct link between endogenous fibrinolysis, endothelial dysfunction, and atherothrombosis in the coronary circulation and may explain the greater efficacy of thrombolytic therapy for myocardial infarction in cigarette smokers.

Objectives: Angiotensin II and bradykinin are potent endogenous vasoactive peptides which may play a role in the regulation of endogenous fibrinolysis and, thereby, contribute to the beneficial actions of ACE inhibitors. The aims of the study were to determine the acute effect of angiotensin II and bradykinin on the local vascular release of tissue plasminogen activator (t-PA) and its inhibitor, plasminogen activator inhibitor type 1 (PAI-1), and the endothelium-derived haemostatic factor, von Willebrand factor (vWf) from the forearm., Methods: Blood flow, and plasma haemostatic and fibrinolytic factors, were measured in both forearms of sixteen healthy men: eight subjects received intra-arterial angiotensin II (5, 50 and 500 pmol/min) which was coinfused with sodium nitroprusside (SNP; 0.3, 1.5 and 7.5 microg/min, respectively), and eight received intra-arterial bradykinin at 10-3000 pmol/min., Results: Despite substantial rises in plasma angiotensin II concentrations (P<0.001) which caused pressor effects (P<0.003) at the highest dose, angiotensin II infusion did not affect local plasma t-PA, PAI-1 or vWf concentrations. In contrast, bradykinin caused substantial dose-dependent increases in blood flow and t-PA release (>100 ng/100 ml of tissue/min) in the infused forearm (P<0. 001 for both) without affecting plasma PAI-1 or vWf concentrations., Conclusions: Despite high local concentrations with breakthrough of significant systemic effects, angiotensin II did not affect acute endothelial cell t-PA, PAI-1 or vWf release in healthy men. In contrast, bradykinin is a potent vasodilator and selective stimulus for acute local t-PA release. This may, at least in part, explain the fibrinolytic actions of ACE inhibitors in heart failure and ischaemic heart disease.

Objective: Effective endogenous fibrinolysis requires rapid release of endothelial tissue plasminogen activator (t-PA). Using the nitric oxide synthase inhibitor, L-NG-monomethylarginine (L-NMMA), we examined the contribution of endogenous nitric oxide to substance P-induced t-PA release in vivo in man., Methods: Blood flow and plasma fibrinolytic and haemostatic factors were measured in both forearms of 8 healthy male volunteers who received unilateral brachial artery infusions of substance P (2-8 pmol/min) and L-NMMA (1-4 micrograms/min)., Results: Substance P caused dose-dependent increases in blood flow (P < 0.001) and plasma t-PA antigen (P = 0.04) and activity (P < 0.001) concentrations confined to the infused forearm, but had no effect on plasminogen activator inhibitor type I (PAI-I) or von Willebrand factor concentrations. In the presence of L-NMMA, substance P again caused significant increases in blood flow (P < 0.001) and t-PA antigen (P = 0.003) and activity (P < 0.001) concentrations but these increases were significantly less than with substance P alone (P < 0.001, P = 0.05 and P < 0.01, respectively). L-NMMA alone significantly reduced blood flow in the infused arm, but had no measurable effect on t-PA or PAI-1 concentrations., Conclusions: The L-arginine/nitric oxide pathway contributes to substance P-induced t-PA release in vivo in man. This provides an important potential mechanism whereby endothelial dysfunction increases the risk of atherothrombosis through a reduction in the acute fibrinolytic capacity.

The effects on blood flow and plasma fibrinolytic and coagulation parameters of intraarterial substance P, an endothelium dependent vasodilator, and sodium nitroprusside, a control endothelium independent vasodilator, were studied in the human forearm circulation. At subsystemic locally active doses, both substance P (2-8 pmol/min) and sodium nitroprusside (2-8 microg/min) caused dose-dependent vasodilatation (p <0.001 for both) without affecting plasma concentrations of PAI-1, von Willebrand factor antigen or factor VIII:C activity. Substance P caused local increases in t-PA antigen and activity (p <0.001) in the infused arm while sodium nitroprusside did not. At higher doses, substance P increased blood flow and t-PA concentrations in the noninfused arm. We conclude that brief, locally active and subsystemic infusions of intraarterial substance P cause a rapid and substantial local release of t-PA which appear to act via a flow and nitric oxide independent mechanism. This model should provide a useful and selective method of assessing the in vivo capacity of the forearm endothelium to release t-PA acutely.

Among patients with recent-onset unstable angina and evidence of ischemia or coronary artery disease, the incidence of subsequent cardiovascular events is high. The aim of this study was to investigate, in this high-risk population, whether unstable angina was associated with abnormalities of tissue-type plasminogen activator (t-PA) or plasminogen activator inhibitor (PAI) activities and whether, in a prospective study, any of these parameters would identify patients with an adverse cardiovascular prognosis. A group of 22 high-risk patients with unstable angina (64% event rate at 3 months) was studied prospectively for 12 weeks, and the fibrinolytic parameters measured at presentation were related to subsequent cardiovascular progress. A group of 20 age- and sex-matched healthy subjects acted as control subjects. Patients who had subsequent cardiovascular events (acute myocardial infarction or severe recurrent angina +/- intervention) had significantly elevated PAI activity at presentation compared with both those who remained event-free (p < 0.05) or with control subjects (p < 0.02). In addition, basal activation of fibrinolysis was demonstrated in unstable angina at presentation; this persisted at 9 weeks in patients with a favorable outcome (p < 0.02 vs control subjects), whereas it was no longer evident in those who developed cardiac events. These findings suggest that measurements of t-PA/PAI activity may reflect the underlying pathophysiologic state and relate to subsequent cardiovascular events in unstable angina.

Some well-described similarities exist between tissue plasminogen activator (t-PA) and von Willebrand factor (vWf) which may suggest a link in either the synthesis or release of both proteins from endothelial cells. To investigate this relationship further immunocytochemical localization of t-PA and vWf was performed in normal tissues and in skin obtained from patients with type I and type III von Willebrand's disease (vWd). Components of the fibrinolytic system were measured at baseline and after venous occlusion in healthy controls and patients with vWd. Patients with severe vWd received intravenous vWf concentrate, followed by desmopressin (DDAVP), to study the plasma response of vWf and t-PA. By immunocytochemical staining, t-PA was demonstrated in endothelial cells of normal skin, kidney and liver and also in the skin of patients with type I and type III vWd. vWf was localized in endothelial cells of all tissues except the specimens from an individual with severe vWd. Basal plasma levels of fibrinolytic components were normal in patients with vWd. Venous occlusion resulted in a rise of fibrinolytic activity in controls and patients with type I, but not type III, vWd. No rise in plasma t-PA was observed following DDAVP in severe vWd, even though near-normalization of plasma vWf levels had been obtained by prior infusion of vWf concentrate. It is concluded that the synthesis of t-PA and vWf is probably regulated by independent processes. Constitutive and regulated release of both proteins occur through different mechanisms and the basal secretion of t-PA is intact in severe vWd.(ABSTRACT TRUNCATED AT 250 WORDS)