Insulin, cortisol and catecholamines do not regulate circadian variations in fibrinolytic activity

Assays to quantify fibrinolysis: strengths and limitations. Communication from the International Society on Thrombosis and Haemostasis Scientific and Standardization Committee on fibrinolysis

Fibrinolysis is a series of enzymatic reactions that degrade insoluble fibrin. Plasminogen activators convert the zymogen plasminogen to the active serine protease plasmin, which cleaves and solubilizes crosslinked fibrin clots into fibrin degradation products. The quantity and quality of fibrinolytic enzymes, their respective inhibitors, and clot structure determine overall fibrinolysis. The quantity of protein can be measured by antigen-based assays, and both quantity and quality can be assessed using functional assays. Furthermore, variations of commonly used assays have been reported, which are tailored to address the role(s) of specific fibrinolytic factors and cellular elements (eg, platelets, neutrophils, and red blood cells). Although the concentration and/or activity of a protein can be quantified, how these individual components contribute to the overall fibrinolysis outcome can be challenging to determine. This difficulty is due to temporal changes within and around the thrombi during the clot breakdown, particularly the fibrin matrix structure, and composition. Furthermore, terms such as "fibrinolytic activity/potential," "plasminogen activation," and "plasmin activity" are often used interchangeably despite having different definitions. The purpose of this review is to 1) summarize the assays measuring fibrinolysis activity and potential, 2) facilitate the interpretation of data generated by these assays, and 3) summarize the strengths and limitations of these assays.

Changes of fibrinolytic system in thrombolytic resuscitation of pulmonary thromboembolism-induced cardiac arrest model

The objective of this study is to explore the changes in the coagulation and fibrinolysis system in an animal model with pulmonary embolism after cardiopulmonary bypass and to provide a theoretical basis for clinical practice. An animal model of cardiac arrest due to pulmonary embolism was established for venous thrombus (10‐15 mL) in the left external jugular vein of 21 pigs. Computed tomography (CT) pulmonary arteriography was performed after the recovery of the underlying state, cardiac arrest state and spontaneous circulation, and then thrombolysis and cardiopulmonary resuscitation (recombinant tissue plasminogen activator [t‐PA] 50 mg) were performed immediately. The changes of tissue factor (TF), tissue factor pathway inhibitor (TFPI), t‐PA and plasminogen activator inhibitor‐1 (PAI‐1) in the blood were detected by ELISA. The blood samples were collected immediately, 1, 2, 4 and 6 hours after the recovery of spontaneous circulation. Data from animals that were successfully resuscitated at different time points were compared using a repeated measures one‐way analysis of variance. Seventeen pigs had cardiac arrest after 10 to 15 mL of thrombus injection, and the other four had cardiac arrest after 5 to 8 mL of additional thrombus. Nine pigs survived 6 hours of cardiopulmonary resuscitation. CT pulmonary angiogram showed pulmonary artery obstruction. TF levels were increased compared with basal status, but there was no statistical difference (P > .05). TFPI levels were higher at 1, 2, 4 and 6 hours after recovery of spontaneous circulation compared with basal state (P < .05); t‐PA levels were higher at cardiac arrest, and immediately after recovery of spontaneous circulation compared with basal state. There was a statistical difference in PAI‐1 level at 1, 2, 4 and 6 hours after recovery of spontaneous circulation (P < .05). There was no statistical difference in PAI‐1 level at each stage compared with basal state (P > .05). TFPI has a certain influence on the coagulation and thrombosis regulation of the body, and the increase in fibrinolytic activity has a positive promoting effect on the thrombolysis. It provided the theoretical basis of clinical treatment of thrombotic diseases.

Patients with the metabolic syndrome and a disturbed cortisol balance display more microalbuminuria

The objective of this study was to investigate whether patients with the metabolic syndrome (MetS) and an imbalance in cortisol metabolism express increased urinary albumin excretion compared to those patients with metabolic syndrome alone. Seventy-four patients with MetS were evaluated using a low-dose dexamethasone suppression test (LDDST) to identify disturbed cortisol balance (cortisol levels > 50 nmol/L after LDDST). The level of albumin in the urine was also evaluated. Disturbed cortisol balance was found in 8% of all evaluated patients with MetS. Microalbuminuria was present significantly more often (p<0.01) in those patients with MetS and an imbalance in cortisol metabolism compared with patients suffering MetS alone (urine albumin: 210 mg/L vs. 26 mg/L, respectively, p<0.01). A substantial percentage of patients with MetS had inappropriate cortisol homeostasis. Of importance, excretion of urinary albumin was increased in these patients. This observation may indicate that this subgroup within the MetS population has a higher cardiovascular risk and possible increased endothelial dysfunction, with a subsequent need for stricter control to prevent cardiovascular morbidity and mortality.

Evidence for pre- to postsynaptic mismatch of the cardiac sympathetic nervous system in ischemic congestive heart failure

Pre- and postsynaptic cardiac sympathetic function is altered in ischemic congestive heart failure (CHF). Whether there is a presynaptic-to-postsynaptic mismatch or whether mismatch is related to adverse cardiac events is unknown.

METHODS

In 13 patients with ischemic CHF and 25 aged-matched healthy volunteers, presynaptic function was measured by PET of (11)C-meta-hydroxyephedrine ((11)C-mHED), a norepinephrine (NE) analog. Postsynaptic function, beta-adrenergic receptor (BAR) density (B'(max)), was measured by imaging (11)C-CGP12177. Myocardial blood flow (MBF) was measured by imaging (15)O-water. Each heart was analyzed both globally and regionally, excluding infarcted regions, and a mismatch score, defined as the ratio of B'(max) to NE uptake (PS(nt))(,) was used to indicate mismatch of post- and presynaptic function.

RESULTS

Global and regional MBF was not different between CHF and healthy subjects. The global measure of PS(nt) was lower in CHF (0.32 +/- 0.34) than that in healthy subjects (0.81 +/- 0.33, P < 0.0001) and in all 12 regions. Global B'(max) tended to be lower in CHF than that in healthy subjects (10.0 +/- 6.4 pmol/mL vs. 13.4 +/- 4.2, P = 0.056) and in all 12 regions. The global mismatch score (B'(max):PS(nt)) in CHF patients was significantly greater than that in healthy subjects (50.3 +/- 50.7 vs. 19.3 +/- 9.7, P = 0.005) and also greater in 11 of 12 regions. After 1.5 y of follow-up, 4 individuals had an adverse outcome (CHF death, new or recurrent sudden death, or progressive CHF leading to transplantation). Three of the 4 had mismatch scores > 3 times that of the healthy subjects or the CHF patients without an adverse outcome.

CONCLUSION

Mismatch between pre- and postsynaptic left ventricular sympathetic function is present in patients with severe CHF and may be more marked in those with adverse outcomes.

11beta-Hydroxysteroid dehydrogenase type 1-driven cortisone reactivation regulates plasminogen activator inhibitor type 1 in adipose tissue of obese women

BACKGROUND

Plasminogen activator inhibitor type 1 (PAI-1) is the main inhibitor of the fibrinolytic system and contributes to an increased risk of atherothrombosis in insulin-resistant obese patients. In adipose tissue, we have shown that PAI-1 is synthesized mainly in the visceral stromal compartment and is positively regulated by glucocorticoids. We have demonstrated that adipose tissue expression of 11beta-hydroxysteroid dehydrogenase type 1 (11beta-HSD-1), an enzyme that catalyzes the conversion of inactive cortisone to active cortisol, is exaggerated in obese patients.

OBJECTIVES

We hypothesized that increased action of 11beta-HSD-1 in adipose tissue of obese subjects may contribute to PAI-1 overproduction.

PATIENTS AND METHODS

Using in situ hybridization, we studied the expression of the mRNAs coding for PAI-1 and 11beta-HSD-1 in the stromal compartment of visceral adipose tissue obtained from obese women. The regulation of PAI-1 secretion from in vitro incubated tissue explants was also investigated.

RESULTS

Regression analysis showed a significant positive linear relationship between PAI-1 and 11beta-HSD-1 mRNAs expression. In vitro incubation of adipose tissue explants demonstrated that cortisone stimulated PAI-1 gene expression and secretion, and that these effects were inhibited by co-incubation with the 11beta-HSD inhibitor, glycyrrhetinic acid.

CONCLUSIONS

Our data demonstrate that 11beta-HSD-1-driven cortisone reactivation regulates adipose PAI-1 synthesis and secretion. They suggest that the increased PAI-1 synthesis and secretion observed in obese patients can be also related, at least in part, to an increased local conversion of cortisone to cortisol. Therefore, local cortisol metabolism in adipose tissue may be involved in increasing the risk of cardiovascular disease in obese subjects.

Plasminogen-activator inhibitor-1 polymorphisms are associated with obesity and fat distribution in the Quebec Family Study: evidence of interactions with menopause

OBJECTIVE

Obesity is associated with increased plasma levels of plasminogen-activator inhibitor-1 (PAI1), the major fibrinolysis inhibitor. PAI1 levels are also increased at menopause, a condition that is associated with fat mass gain, especially in the abdominal area.

DESIGN

We hypothesized that genetic variations within PAI1 gene are related to the amount of body fat and its regional distribution. We genotyped 666 subjects of the Quebec Family Study for five PAI1 gene polymorphisms. Stratified analyses were performed with analysis of covariance in men (n = 280) and women (n = 386) separately.

RESULTS

PAI1-675 4G/5G polymorphism was strongly associated with body mass index (P < or = 0.01) and fat mass (P < or = 0.05) in women. The PAI1-675 4G/5G promoter polymorphism and the c.43G<A (p.A15T, rs6092) variant within the exon 1 were associated with abdominal visceral fat but only in postmenopausal women (P < or = 0.05). More specifically, homozygotes for the -675 5G and the 43A alleles had about 50% more visceral fat compared to carriers of the -675 4G allele as well as carriers of the 43G allele. No association was observed in men.

CONCLUSION

Taken together, these results suggest that the PAI1 gene is associated with obesity and may modulate the changes in adipose tissue distribution generally observed at menopause.

Coagulation, fibrinolysis, and recanalization after acute deep venous thrombosis

OBJECTIVE

Recanalization is common after acute deep venous thrombosis, but the factors that contribute to its variable extent are unknown. The purpose of this study was to examine the relationship between recanalization and plasma markers of coagulation and fibrinolysis.

METHODS

Subjects with an ultrasound-confirmed deep venous thrombosis had prothrombin fragment 1+2 (F 1+2), tissue plasminogen activator (t-PA) activity, plasminogen activator inhibitor (PAI-1) activity, and t-PA antigen levels determined before anticoagulation therapy. Ultrasound and plasma studies were repeated at 14 days, 1 month, and every 3 months for 1 year.

RESULTS

Among 71 enrolled subjects, F 1+2 levels normalized within 14 days. The mean t-PA activity was within the normal range at all follow-up intervals. However, the mean t-PA antigen (10.7 plus minus 10.5 to 13.6 plus minus 13.5 ng/mL; P =.04) and PAI-1 (9.0 plus minus 8.1 to 13.2 plus minus 17.3 U/mL; P =.05) levels increased between the time of presentation and day 14. The mean reduction in thrombus score among 44 patients who completed 9 months of follow-up was 60.9% (plus minus 42.1%). Percent recanalization was directly associated with initial t-PA activity levels (R =.4; P =.006) and inversely related to F 1+2 (R = minus sign. 5; P =.004), t-PA antigen (R = minus sign.5, P =.002), and PAI-1 (r = minus sign. 5, P =.001) levels. However, only initial F 1+2 (P =.0009) and t-PA antigen (P =.004) levels were independent predictors of the degree of recanalization.

CONCLUSION

Although the mechanisms by which the venous lumen is restored are still being elucidated, recanalization is inversely related to levels of activated coagulation (F 1+2) and fibrinolytic inhibition (t-PA antigen) at the time of presentation.

Effect of activation and inhibition of the renin-angiotensin system on plasma PAI-1

Increased plasma renin activity (PRA) has been associated with an increased risk of myocardial infarction (MI), whereas angiotensin-converting enzyme (ACE) inhibition appears to reduce the risk of recurrent MI in patients with left ventricular dysfunction. These observations may be partially explained by an interaction between the renin-angiotensin system (RAS) and fibrinolytic system. To test this hypothesis, we examined the effect of salt depletion on tissue-type plasminogen activator (tPA) antigen and plasminogen activator inhibitor-1 (PAI-1) activity and antigen in normotensive subjects in the presence and absence of quinapril (40 mg BID). Under low (10 mmol/d) and high (200 mmol/d) salt conditions there was significant diurnal variation in PAI-1 antigen and activity and tPA antigen. Morning (8 AM through 2 PM) PAI-1 antigen levels were significantly higher during low salt intake compared with high salt intake conditions (ANOVA, F=5.8, P=0.048). PAI-1 antigen correlated with aldosterone (r=0.56, P<10(-7)) during low salt intake. ACE inhibition significantly decreased 24-hour (ANOVA for 24 hours, F=6. 7, P=0.04) and morning (F=24, P=0.002) PAI-1 antigen and PAI-1 activity (F=6.48, P=0.038) but did not alter tPA antigen. Thus, the mean morning PAI-1 antigen concentration was significantly higher during low salt intake than during either high salt intake or low salt intake and concomitant ACE inhibition (22.7+/-4.6 versus 16. 1+/-3.3 and 16.3+/-3.7 ng/mL, respectively; P<0.05). This study provides evidence of a direct functional link between the RAS and fibrinolytic system in humans. The data suggest that ACE inhibition has the potential to reduce the incidence of thrombotic cardiovascular events by blunting the morning peak in PAI-1.

Effect of a Change in the Sleep/Wake Cycle on the Diurnal Variation of Fibrinolytic Parameters

The mechanism underlying the circadian rhythm of fibrinolysis is not well understood. To evaluate the influences of wakefulness and of the intrinsic circadian rhythm on fibrinolytic activity, we examined diurnal changes (8:00 am vs. 8:00 pm) in plasminogen activator inhibitor-1 (PAI-1) activity, tissue plasminogen activator (t-PA) antigen levels, and t-PA activity, as well as in plasma serum cortisol levels, in 10 healthy males (21 +/- 2 years) for two consecutive days. On the first day, subjects remained awake all day and night. They slept during the daytime (8:30 am to 5:30 pm) on the following day. PAI-1 activity and cortisol levels were significantly decreased, and t-PA activity tended to increase during the daytime on the first day. On the morning following overnight wakefulness, PAI-1 activity and cortisol levels did not return to the levels of the previous morning. On the second day, the afternoon decrease in PAI-1 activity, but not cortisol levels, was still observed, although its magnitude was substantially attenuated. No significant diurnal changes were observed in the levels of t-PA antigen throughout the study period. These findings suggest that the diurnal variation of fibrinolytic activity may be governed by an intrinsic circadian rhythm of PAI-1, which can be modified by a change in the time of wakefulness.

Effects of endurance training on the circadian rhythm of fibrinolysis in men and women

This randomized study compared the fibrinolytic circadian rhythm of healthy older men and older women (average age 66 +/- 5), before and after 6 months of endurance training versus stretching controls. Compared with men, women at baseline had similar rhythms for tissue plasminogen activator (t-PA) activity and plasminogen activator inhibitor 1 (PAI-1) activity, but lower levels of total t-PA antigen. In men (N = 16), endurance training increased VO2max 15% (P < 0.001), while decreasing PAI-1 activity 37% (P = 0.034) and total t-PA antigen 18% (P = 0.0003) between midnight and 6 a.m., but did not affect t-PA activity. In women (N = 9), endurance training increased VO2max 18% (P = 0.003), and increased t-PA activity 20% (P = 0.027) and total t-PA antigen 55% (P = 0.007) between 10 p.m. and 4 a.m., but had no effect on PAI-1 activity. After endurance training there were no significant differences in the fibrinolytic circadian rhythm of men versus women. Six months of nonaerobic stretching had no effect on VO2max or fibrinolysis in men (N = 11) or women (N = 8). This study indicates that potentially favorable changes occur in fibrinolytic factors after endurance training in older men and older women.

The circulatory regulation of TPA and UPA secretion, clearance, and inhibition during exercise and during the infusion of isoproterenol and phenylephrine

BACKGROUND

Exercise to exhaustion and infusions of isoproterenol and phenylephrine were used to study interactions between plasminogen activator regulation and the control of regional blood flow in 10 healthy males.

METHODS AND RESULTS

Experimental measurements of cardiac output, heart rate, tissue plasminogen activator (TPA), urokinase plasminogen activator (UPA), plasminogen activator inhibitor (PAI-1), C1-inhibitor, and TPA/C1-inhibitor complex during the infusions and exercise were used to develop a comprehensive fluid-phase model of the circulatory regulation of fibrinolysis. alpha- and beta-adrenergic agonists increased TPA and UPA in plasma by different mechanisms: Phenylephrine decreased hepatic blood flow and thus clearance while isoproterenol stimulated increased secretion of TPA and UPA. Exercise to exhaustion increased TPA and UPA through a combination of increased secretion and decreased clearance. The time course of UPA and TPA release were similar, but the magnitude of their secretion responses differed. In vivo, C1-inhibitor bound to TPA at a rate of 553 mol-1.s-1. C1-inhibitor contributed equally with PAI-1 to TPA inhibition when active PAI-1 levels were low (20 to 50 pmol/L) but was less important when active PAI-1 levels were high.

CONCLUSIONS

We conclude that secretion, inhibition, clearance, and regional blood flow effects must all be taken into account when evaluating changes in plasminogen activator levels.

On the action of a heparan-like glycosaminoglycan (Hemovasal) on the mechanism of haemostasis and fibrinolysis

Hemovasal produced by Manetti-Roberts, Florence, Italy, is a glycosaminoglycan obtained from porcine intestinal mucosa which belongs to the family of heparan sulfates. The substance was examined On 36 male survivors of myocardial infarction with an interval of at least 6 months after the acute event. No anticoagulants were given and ASA was withdrawn at least 2 weeks before the trial. Hemovasal was administered in 3 different i.m. doses as single injections. A further group received a daily oral dose of 300 mg for one week. A comparable placebo group of patients as well as a group of healthy volunteers was run in parallel. The coagulation profile showed only a slight prolongation of the aPTT, a trace of diminution of Antithrombin III and no activation of Heparin cofactor II. The fibrinolytic system showed an enhancement of the diurnal increase of t-PA without an alteration of the total increase of this activity. There was a considerable and highly significant diminution of the PAI-1 activity. This was dose dependent and could be found after i.m. as well as after oral administration. It was assumed that the thrombolytic effect which was repeatedly described was a consequence of the diminution of PAI-1.

Circadian variation of plasminogen activator activity, plasminogen activator inhibition and plasmin inhibition in aorta, heart, brain and lungs of the rat. Sex-related differences

Plasminogen activator activity (PAA), t-PA antigen level, plasminogen activator inhibition (PAI) and plasmin inhibition (PI) showed a circadian variation in rat aorta, heart, brain, and lungs of both sexes, but in a different way depending on the organ and the fibrinolytic parameter studied and the sex as well. In general, the lowest values of PAA and t-PA antigen were found in the early morning and the highest values in late afternoon, while PAI or PI showed the opposite pattern (with the exception of lungs). In kidneys and liver the fibrinolytic parameters studied showed no circadian variation. Sex-related differences, mostly quantitative, were noted in aorta, heart, brain and kidneys, with lower PAA and t-PA antigen and higher PAI or PI in the male than in the female.

Evidence for the role of dialysis hypoxemia in the pathogenesis of hemodialysis-induced rise in tissue-type plasminogen activator

It is well known that hemodialysis (HD) causes a rise in plasma tissue-type plasminogen activator (t-PA). Although there have been several suggested mechanisms responsible for this effect of HD, the precise cause has not been well understood yet. Another complication of HD, when performed with acetate-containing dialysate, is hypoxemia, which is commonly observed during the first hour of the session. The purpose of this study was to investigate the relationship between dialysis hypoxemia and HD-induced t-PA changes during the first two hours of HD. HD caused significant increase in plasma t-PA antigen levels. When individual t-PA profiles versus time were examined, two patterns were observed. Whilst ten subjects (%56) experienced minimal or no increase, t-PA antigen level of the remaining eight subjects began to rise at 30 minutes and continued at that level up to 90 minutes, when the last samples were drawn. The courses of pO2 were also different; whilst the former group had "early-onset and short-term" hypoxemia, the latter had "late-onset and prolonged" hypoxemia. The amount of increase in t-PA antigen and the amount of decrease in pO2 were correlated at 60 and 90 minutes of the HD session. Thus, it is concluded that dialysis hypoxemia may contribute to HD-induced rise in plasma t-PA levels. Further studies comparing different dialysates and dialyser membranes are required to confirm this hypothesis.

Plasminogen activator inhibitor and von Willebrand factor in polymyalgia rheumatica

Endothelial cell products, plasminogen activator inhibitor (PAI) and von Willebrand factor (vWF), were assayed in 25 patients with newly-diagnosed and untreated polymyalgia rheumatica (PMR), before and after three and 12 months of corticosteroid treatment. The mean values of PAI and vWF, and also the levels of acute phase reactants (erythrocyte sedimentation rate, fibrinogen, haptoglobin, orosomucoid, C-reactive protein) and platelet counts, were elevated in the active untreated disease. In contrast to the acute phase proteins, both PAI and vWF remained increased after three and 12 months of glucocorticoid treatment. This suggested an active vasculitis, despite a clinically-inactive disease. Particularly high levels of vWF both before and after glucocorticoid therapy were found in two patients who subsequently developed vascular complications during the follow-up period.

Fibrinolytic response during exercise and epinephrine infusion in the same subjects

To determine whether exercise-induced increases in tissue plasminogen activator (t-PA) were related to plasma epinephrine concentration during exercise, 14 healthy men (aged 24 to 62 years) were studied during epinephrine infusions (10, 25 and 50 ng/kg per min) and graded supine bicycle exercise, beginning at 33 W and increasing in 33-W increments until exhaustion. Plasma epinephrine, active and total t-PA, active plasminogen activator inhibitor type 1 (PAI-1) and t-PA/PAI-1 complex concentrations were measured at each exercise and infusion level. During epinephrine infusion, active and total t-PA levels increased linearly with the plasma epinephrine concentration (respective slopes [+/- SEM] of 0.062 +/- 0.003 and 0.076 +/- 0.003 pmol/ng epinephrine). During exercise, t-PA levels did not increase until plasma epinephrine levels increased, after which both active and total t-PA levels again increased linearly with the plasma epinephrine concentration, but at twice the rate observed with epinephrine infusion (0.131 +/- 0.005 and 0.147 +/- 0.005 pmol/ng, respectively). The t-PA level in blood was directly proportional to the plasma epinephrine concentration during both exercise and epinephrine infusion, suggesting that epinephrine release during exercise stimulates t-PA secretion. In these healthy subjects, active plasminogen activator inhibitor type 1 and t-PA/PAI-1 complex levels were low (41 +/- 11 and 21 +/- 5 pmol/liter, respectively) and did not change significantly during exercise or epinephrine infusion. It is concluded that approximately 50% of the increase in t-PA during exercise is due to stimulated release of t-PA by epinephrine.(ABSTRACT TRUNCATED AT 250 WORDS)

The acute effect of smoking on platelet and endothelial release reaction is suppressed in chronic smokers

Whilst increased plasma beta-thromboglobulin (beta TG), platelet factor 4 and thrombospondin levels are regarded as reflecting the release reaction of platelets, tissue-type plasminogen activator (t-PA) and plasminogen activator inhibitor-1 (PAI-1) levels represent endothelial release reaction and/or damage. In this study including 12 smokers and 9 nonsmokers, we investigated the acute and chronic effect of smoking on these parameters and antithrombin III, protein S and fibrinogen, as well. Nonsmokers were found to have somewhat higher plasma levels of beta TG, t-PA and PAI-1 than chronic smokers, and 30 minutes after smoking two cigarettes, these levels and protein S levels of nonsmokers showed more prominent increases than of chronic smokers. It is speculated that chronic exposure to cigarette smoke may cause "exhaustion" or "receptor down-regulation" of platelets and endothelial cells, resulting with diminished release reaction of platelets and endothelium in response to acute smoking.

Reference values of hemostasis related factors of healthy Japanese adults. I: Circadian fluctuation

The circadian fluctuation of hemostasis related parameters was examined on 16 healthy Japanese adults (male 9, female 7). Twenty one parameters were measured in this study, i.e. fibrinogen, the activity of F.II, F.V., F.VII, F.VIII, F.IX, F.X., F.XI, F.XII, antithrombin III, plasminogen, alpha 2-antiplasmin, as well as the antigen level of F.IX, von Willebrand Factor, protein C, tissue-type plasminogen activator (tPA), plasminogen activator inhibitor-1 (PAI-1), beta-thromboglobulin, platelet factor 4, fibrinopeptide A, plasmin-alpha 2-antiplasmin complex and FDP. Fluctuation was not significant in almost all of the parameters except F.VIII, F.IX, beta-thromboglobulin, platelet factor 4, tPA and PAI-1. Although the fluctuations of F.VIII, F.IX, beta-thromboglobulin and platelet factor 4 were statistically significant, they remained within the normal ranges. On the other hand, tPA and free PAI-1 showed significant circadian fluctuation, of which levels were highest at 9:00. It was postulated that the significant circadian fluctuation of fibrinolytic activity will be regulated by the balance between tPA and PAI-1 in plasma.