Circadian fluctuations in plasma levels of tissue plasminogen activator antigen and plasminogen activator inhibitor activity

Daily fluctuations of t-PA antigen and PAM activity were measured in plasma samples of physically active young healthy volunteers (group 1, n = 11; age range 20–38 years) and compared to data obtained from resting patients (group 11, n = 23; age range 44–67 years) suffering from moderate valvular disease without evidence for inflammatory, neoplastic, or thrombosis-related diseases (e.g. deep vein thrombosis, coronary artery disease). t-PA antigen concentration showed a similar diurnal pattern in both study groups with the peak value at 06:00 but was significantly increased in the higher aged group at all collection times. PAM activity had its acrophase in both groups at or around 03:00 but no age-dependent differences could be demonstrated. t-PA antigen as well as PAI-1 activity fluctuations conserved their typical pattern despite differences in physical activity in the study groups.     

Plasma tissue plasminogen activator and plasminogen activator inhibitor-1 levels in acute myocardial infarction

The cause of the circadian variation in the incidence of acute myocardial infarction (AMI) has not been identified. Tissue plasminogen activator (t-PA) and plasminogen activator inhibitor-1 (PAI-1) have opposing effects on thrombi. Hence, the extent of the clot, the size of the infarct and outcome of patients could depend on t-PA and PAI-1 levels. In an effort to elucidate the pathophysiologic basis of circadian variation of AMI, we investigated the presence of a possible corresponding circadian variation in the levels of endogenous t-PA and PAI-1 in patients diagnosed to have AMI and the effects of hypertension, diabetes and site of the infarct on these levels. We estimated the levels of t-PA and PAI-1 in platelet-poor plasma of 42 patients with AMI on admission, using the enzyme-linked immunosorbant assay. Although not statistically significant, patients having an AMI in the morning hours had the highest t-PA:PAI-1 ratio. The normal circadian variation in PAI-1 levels was lost in patients with AMI, probably due to the disease process. Also, the t-PA levels in hypertensive patients were significantly lower than in nonhypertensives. PAI-1 levels were also significantly lower in patients with anteroseptal than in inferior and anterolateral AMI. This relationship between the fibrinolytic potential and the site of infarction needs further study. Furthermore, t-PA levels on admission were significantly lower in survivors and may have a predictive value in determining the outcome.     

Tissue type plasminogen activator antigen and activity in sickle cell disease.

To investigate the hypothesis that diminished endothelial fibrinolysis is present in sickle cell (SS) disease plasma, tissue type plasminogen activator (t-PA) antigen titres were measured before and after a standard stimulus of endothelial t-PA release (venous occlusion of the arm), and plasma t-PA activities after venous occlusion in 33 subjects with SS disease and in 32 healthy subjects. Mean plasma t-PA antigen titres before and after venous occlusion, and mean plasma t-PA activities after venous occlusion did not differ significantly between SS patients and normal subjects. No significant differences in mean t-PA antigen and activity were observed between samples taken from inpatients being treated for acute pain crisis (18 subjects, 30 samples) and samples taken from subjects in the steady state (23 subjects, 26 samples). No consistent differences were seen between painful crisis and steady state samples in eight SS patients studied while in crisis and in the steady state. No correlation was observed between any fibrinolytic variable in SS patients and the overall severity of microvascular occlusive disease as measured by a standard scoring system. It is concluded that the capacity of endothelium to synthesise and release t-PA is not impaired in SS disease, and that excessive inhibition of released t-PA, leading to reduced t-PA activity in plasma is also not a feature of SS disease, either in the steady state or during painful crisis.     

Familial thrombophila associated with high levels of plasminogen activator inhibitor

A family with defective fibrinolytic abnormalities and recurrent thrombotic events is described. Impaired fibrinolysis was associated with high activity and concentration of fast-acting plasminogen activators inhibitor (PAI-1). Acquired conditions associated with PAI-1 increase were excluded. After venous occlusion testing, a different behaviour of fibrinolytic activity inhibition was seen in the family members. In the propositus and in two relatives only tissue (t-PA) plasminogen activity inhibition was found; in two other members, both t-PA and urokinase-type plasminogen activities were completely inhibited by the high PAI-1 levels. This fibrinolytic defect seems to be familial and transmitted as an autosomal trait.     

Tissue plasminogen activator and plasminogen activator inhibitor in patients with liver cirrhosis

The behaviour of tissue plasminogen activator (t-PA) and t-PA inhibitor (PAI) was studied in patients with decompensated liver cirrhosis. t-PA antigen showed a 3-fold significant increase with respect to healthy volunteers. t-PA activity in these patients did not significantly differ from that found in the controls, but the specific activity of t-PA was significantly lowered by 63%. PAI activity was significantly reduced in cirrhosis (−67%), while PAI-1 antigen was increased by 24%. Venous occlusion of the arm for 20min induced similar increases of t-PA antigen both in normal subjects and cirrhotic patients. These findings show that the total amount of t-PA is enhanced in liver cirrhosis, with no increase of t-PA activity due to the capacity of PAI to bind increased circulating t-PA antigen. The increased total amount of t-PA in cirrhotic patients could be explained in terms of a reduced clearance by the hepato-endothelial system.     

Acute effects of moderate alcohol consumption on fibrinolytic factors in healthy middle-aged men

Acute effects of moderate alcohol consumption on fibrinolytic factors were investigated in 8 healthy middle-aged men (between 45 and 55 years) in a carefully controlled study. Alcohol consumption comprised two glasses of red wine during dinner and two glasses of Dutch gin in combination with a snack during the evening (40g of alcohol in total). During the control treatment corresponding volumes of mineral water were consumed. Blood samples were drawn before dinner (around 15:00), 1 h after dinner (around 19:00), 1 h after the snack (around 23:00) and the next morning (around 08:00). PAI activity was increased by 230% (p<0.001) after alcohol consumption at the late evening measurement. PAI-1 antigen levels, however, were not significantly affected. The specific activity of PAI (activity/antigen quotient) was significantly increased by alcohol consumption at all three times of measurement after dinner. As a consequence tissue-type plasminogen activator (t-PA) activity was reduced by up to 95% (p<0.001), around 23:00. Levels of t-PA antigen, on the other hand, were increased after alcohol consumption (up to +42%, p<0.01). No effects of alcohol consumption on the urokinase plasminogen activator (u-PA) system were observed. We conclude that shortly after moderate alcohol consumption both t-PA antigen and PAI activity levels are increased, resulting, however, in a decreased activity of t-PA. Increased PAI activity persists after an overnight fast.     

Temporal correlation of some endocrine circadian rhythms in elderly subjects

The aim of this chronobiological study was to investigate temporal correlations in the circadian patterns of 6 hormones, namely somatotrophic hormone (STH), prolactin (PRL), cortisol (F), aldosterone (ALD), insulin (IRI) and C-peptide (CP), assayed in systemic blood serum drawn at 07:00, 10:00, 13:00, 16:00, 19:00 and 22:00 h from an antecubital vein in 19 young subjects (aged 20-29 yr, comprising 10 males and 9 females; and 20 elderly subjects (aged 70-81 yr, comprising 10 males and 10 females). All subjects were sampled on a normal dietary sodium intake (120-140 mEq/24h) while following a social routine of diurnal activity (07:00-23:00) and nocturnal rest (23:00-07:00). Time-qualified data were analyzed by lead-lag correlation and by cosinor analysis. According to the lead-lag correlation findings, it would appear that the correlation which exists between several time-qualified series in young subjects is no longer present in elderly subjects. The circadian rhythms which were found to have lost their temporal correlations with advancing age were those between STH and IRI, STH and ALD, PRL and IRI, PRL and CP, and ALD and CP. It should be noted that the correlation between hormonal rhythms breaks down mainly on account of a peculiar age-related change in the magnitude of the circadian fluctuation. This chronological decline in amplitude led to the conclusion that the senescence of endocrine rhythmic functions is a biological phenomenon characterized by altered circadian variability.     

Fibrinolytic response in malignancy

Fibrinolytic response was investigated in 71 patients with different malignancies and compared with findings in 30 healthy persons. Euglobulin lysis time, fibrinolytic activity on fibrin plate, tissue plasminogen activator (t-PA) activity and antigen before and after venous occlusion and the fast-acting inhibitor to t-PA (PA-inhibitor) were performed. Fifteen patients (21%) showed low fibrinolytic activity on fibrin plate after venous occlusion (low responders), whereas all control subjects showed a positive response (p < 0.03). t-PA activity was significantly lower in patients (p < 0.003) and t-PA antigen showed no significant differences between patients and controls in post-occlusion samples. PA-inhibitor was significantly higher in patients (p < 0.0002). We conclude that defective fibrinolysis in malignancy, resulting of highly increased PA-inhibitor levels in combination with low t-PA activity, and may have pathogenetic implications.     

慢性肾脏疾病血清和尿液纤溶活性物质的改变及临床意义

目的探讨慢性肾脏疾病血清和尿液纤溶活性物质的改变及其临床意义。方法选择38例慢性肾小球肾炎(CGN),28例肾病综合征(NS),36例非透析治疗的慢性肾功能不全(CRF)和20例正常对照作为研究对象,应用ELISA法检测血清和尿液中组织型纤溶酶原激活剂(t-PA)和纤溶酶原激活物抑制剂-1(PAI-1)的浓度,同时分析尿中t-PA和PAI-1的水平与血t-PA、PAI-1、血肌酐和24h尿蛋白总量之间相关性。结果慢性肾脏疾病出现血清t-PA、PAI-1升高,尿液t-PA、PAI-1降低,其中尿液t-PA、PAI-1的改变独立于血清,不受血肌酐和24h尿蛋白定量的影响。结论慢性肾脏疾病患者存在纤溶活性物质的异常,其中尿液纤溶活性物质的改变可反应肾脏内皮细胞损伤。     

Levels of tissue-type plasminogen activator and plasminogen activator inhibitor 1 in disseminated intravascular coagulation syndrome

Since disseminated intravascular coagulation (DIC) may directly reflect the abnormal regulation of the fibrinolytic system by endothelial cells, we have measured the levels of tissue-type plasminogen activator (t-PA), type 1 PA inhibitor (PAI-1) and t-PA . PAI-1 complex which is formed as a result of interaction on the two factors, in the plasma of patients with DIC (n = 51) and healthy controls (n = 42). Antigens of t-PA, PAI-1 and t-PA . PAI-1 complex were significantly increased in the DIC plasma (36.4 +/- 25.1, 106.8 +/- 54.7 and 46.6 +/- 34.5 ng/ml, respectively) compared with those in normal plasma (8.5 +/- 4.3, 54.4 +/- 21.2 and 8.6 +/- 3.5 ng/ml, respectively). The molar ratio of t-PA to PAI-1 was much higher in the DIC plasma (1:3) than in normal plasma (1:6), which caused enhancement of the whole fibrinolytic activity in the DIC plasma. These changes resulted in significant consumption of plasminogen, alpha 2-plasmin inhibitor (alpha 2-PI) and a significant increase of plasmin . alpha 2-PI complex (PPI) and D-dimer. These results suggest that t-PA and its specific inhibitor PAI-1 both of which are secreted from endothelial cells into blood, play an important role on the progress of DIC.     

Fibrinolytic effect of gemfibrozil versus placebo administration in response to venous occlusion

Impact of hypertriglyceridemia on atherosclerotic vascular disease and thromboembolic events is recently emphasized by primary prevention studies on the development of coronary artery disease. A randomized double-blind study was carried out with gemfibrozil (600 mg b.i.d.) versus placebo in 20 patients (12 males and 8 females, age 52±3 years, BMI 24.2±0.4) suffering from primary hypertriglyceridemia (Fredrickson's type IV). After a 4-week stabilization period in which administration of lipid-lowering drugs was stopped and an isocaloric diet was prescribed, patients were randomized into two groups. Each group was treated for a 12 week period with gemfibrozil (10 patients) or placebo (10 patients) in a double-blind fashion.Every 4 weeks triglycerides, total cholesterol, HDL-cholesterol, blood glucose and Apolipoproteins A1 and B were determined.At baseline and at the end of the treatment period a venous occlusion test was performed in all subjects. Before and after 10 min venous stasis were measured: t-PA antigen, PAI activity, fibrinogen, plasminogen, Factor VII and haematocrit.In the gemfibrozil-treated group a significant decrease of triglycerides and a significant increase of HDL-C was found. During gemfibrozil treatment a significant reduction of Factor VII, fibrinogen and plasminogen levels either before or after venous occlusion was also observed. After 12 weeks of treatment in the gemfibrozil group the release of t-PA in response to venous occlusion was significantly higher and plasma PAI activity was significantly lower than in placebo group, suggesting a profibrinolytic effect of the drug.     

Age-related changes in vasomotor reflex control of calf venous capacitance response to lower body negative pressure in humans

The present study was performed to test the hypothesis that calf venous capacitance would be reduced by mild gravitational stress through a vasomotor reflex in humans, and this response could be diminished with advancing age. Nine young (31 +/- 1 years, mean +/- SE) and 9 elderly (69 +/- 1 years) healthy males were exposed to a lower body negative pressure (LBNP) of 15 mmHg. Venous occlusion plethysmography was used to measure calf venous capacitance and calf blood flow. Muscle sympathetic nerve activity (MSNA) was recorded microneurographically from the tibial nerve along with cardiovascular variables. It was found that baseline MSNA was higher [21 +/- 4 (mean +/- SE) vs. 37 +/- 5 bursts x min(-1), young vs. elderly; p < 0.05] and calf venous capacitance was lower (1.71 +/- 0.12 vs. 1.44 +/- 0.10, ml x 100 ml(-1), young vs. elderly; p < 0.05) in the elderly group. At 15 mmHg-LBNP, heart rate and mean arterial pressure both remained unchanged, MSNA was enhanced, and calf blood flow was reduced in all subjects. Calf venous capacitance during LBNP decreased in the young, but did not change in the elderly. A significant negative correlation between percent changes in MSNA and percent changes in calf venous capacitance existed in the young group (y = 20.171x-11.863, r = 20.682; p = 0.0432), but disappeared in the elderly group. The ratio of percent changes in calf venous capacitance to percent changes in MSNA was markedly lower in the elderly (p < 0.01). In conclusion, these results substantiate our hypothesis that calf venous capacitance is reduced by mild LBNP through the vasomotor reflex, and this response is diminished in the elderly.     

Plasminogen activator and plasminogen activator inhibitor activities in a reference population

The influence of age, gender, and aspirin ingestion on plasma levels of tissue plasminogen activator (t-PA) and plasminogen activator inhibitor-1 (PAI-1) activities was studied in a reference population of 35 men and 35 women between the ages of 20 and 65 years. The t-PA values (mean +/- SD) in the women before and after 5 minutes of venous occlusion were 3.8 +/- 1.4 and 7.8 +/- 4.4 micrograms/L, respectively; in men these values were 3.3 +/- 1.2 and 8.8 +/- 8.9 micrograms/L. Men had higher mean PAI levels than did women (5.0 vs. 2.5 kU/L). T-PA showed an inverse relationship to PAI in both sexes. There was a negative correlation of t-PA levels with age, whereas PAI levels were positively correlated. The ingestion of a single dose of aspirin (650 mg) did not alter PAI or t-PA activities. This study indicates that factors such as age and sex may need to be considered when reference populations are developed for clinical studies of fibrinolysis.     

Increased plasma levels of a rapid inhibitor of tissue plasminogen activator in young survivors of myocardial infarction

Certain risk factors for myocardial infarction have been linked with disturbances in fibrinolytic activity. The recent development in our laboratory of new sensitive and specific methods for determination of tissue plasminogen activator (t-PA) activity and antigen, as well as the discovery of a new rapid inhibitor of this enzyme, enabled us to study fibrinolytic function in detail in a representative population of postinfarction patients. Seventy-one patients (62 men and 9 women) who had survived a myocardial infarction before the age of 45 were compared with 50 healthy subjects of similar age, three years after the infarction. Low t-PA activity after venous occlusion, mostly explained by high plasma levels of the t-PA inhibitor and to some extent by impaired release of t-PA from the vessel wall, was a frequent finding in the patients. The level of t-PA inhibitor was positively and significantly correlated with levels of serum triglycerides. Our data suggest that reduced fibrinolytic capacity due to increased plasma levels of a rapid inhibitor of t-PA may have pathogenetic importance in myocardial infarction, particularly in patients with hypertriglyceridemia.     

Fibrinolysis after delivery: caesarean section versus vaginal delivery

Caesarean section is associated with higher risk of thromboembolism than normal vaginal delivery. In order to elucidate if altered fibrinolysis contributes to this increased risk, 15 women who delivered by Caesarean section were observed in the 37th to 40th week of pregnancy, 1 h, 3 and 10 days after delivery and compared to 15 women who delivered vaginally. Before delivery no differences in fibrinolytic variables were observed between the two groups. The immediate post-delivery period was associated with significant (all p<0.05) and similar increases in tissue-type plasminogen activator (t-PA) activity (149 vs 129%, all figures: Caesarean section vs vaginal delivery) and t-PA antigen (46 vs 75%) and significant (all p<0.05) decreases in plasminogen activator inhibitor (PAI) activity (66 vs 69%) and PAI-1 antigen (74 vs 82%) in both groups. Only euglobulin activity was less enhanced (60 vs 159% increase, p<0.05). Three days after delivery all variables, except PAI activity, decreased significantly (all p<0.05) compared to values 1 h after delivery (t-PA activity: 37 vs 41%; t-PA antigen: 43 vs 51%; PAI-1 antigen: 80 vs 58%) and similarly in both groups. From the 3rd to the 10th day euglobulin activity, t-PA activity and t-PA antigen slightly increased. The venous occlusion test, which was performed before delivery, 3 and 10 days after delivery revealed no significant differences in fibrinolytic responses to such stimulation between the two groups investigated. It was concluded that changes in t-PA and PAI-1 observed after Caesarean section are not significantly different from those observed after normal vaginal delivery and therefore presumably do not contribute to increased risk of thromboembolism after Caesarean section.     

Effect of nerve block on t-PA release by venous occlusion

In order to investigate the influence of neural blockade on tissue plasminogen activator (t-PA) release by venous occlusion, we compared the increase in t-PA and fibrinolytic activity in the euglobulin fraction initiated by cubital venous occlusion (100 mmHg for 10 min), in pre-neural block and post-neural block states, in 7 cases. In all patients, the supra-clavicular approach was used to obtain a brachial plexus block and venous occlusion was achieved at the cubital levels on the ipsilateral arm. The euglobulin fibrinolytic activity before venous occlusion was 100.9±27.5 BAU in the pre-nerve block state and 102.7±29.4 BAU in the post-nerve block state (p>0.5). The t-PA antigen level before venous occlusion was 3.5±1.2ng/ml in the pre-nerve block state and 4.0±1.0 ng/ml in the post-nerve block state (p>0.05). The increase in the euglobulin fibrinolytic activity after venous occlusion was 18.0±16.7 BAU in the pre-nerve block state, and 18.3±15.6 BAU in the post-nerve block state (p>0.5). The increase in the t-PA antigen levels after venous occlusion was 3.0±2.0 ng/ml in the pre-nerve block state and 3.0±2.1ng/ml in the post-nerve block state (p>0.5). These findings suggest that the peripheral nervous system does not exert any influence on t-PA release during venous occlusion.     

Venous occlusion test: Assessment of fibrinolytic capacity by D-dimer latex agglutination test

The fibrinolytic capacity of 36 individuals was investigated by venous occlusion (VO) test. The specific components of fibrinolysis — plasminogen activator (t-PA) and plasminogen activator inhibitor activity (PAI) - were measured before and after 20 min VO and the subjects ,were divided into good (n=24) and poor (n=12) responders according to the presence of residual PAI activity after VO test. The ranking of the patients according to residual PAI activity correlated closely with that obtained by an index entitled the net fibrinolytic capacity (nFC) that expresses the ability of secreted t-PA to overcome PAI activity. Residual PAI and nFC were further compared with a recently published screening method based on fibrin degradation (D-dimer concentration) in a clotted blood sample obtained after VO. The D-dimer concentrations measured by a semiquantitative latex agglutination test agreed closely with the ranking of patients by residual PAI and nFC and had a close correlation with the concentrations of the specific components of fibrinolysis. We conclude that D-dimer test after 20 min VO qualifies well for screening of impaired fibrinolytic capacity.     

Vascular bed specific alterations in coagulation and fibrinolytic parameters in young women following myocardial infarction, lacunar cerebral infarction and deep vein thrombosis

The possible existence of distinctive, vascular bed specific alterations of coagulation and fibrinolytic parameters associated with three different types of thrombosis was investigated in young women (n = 68, <45 years at onset of the event) following myocardial infarction (MI) (n = 22), lacunar cerebral infarction (LACI) (n = 16), idiopathic deep vein thrombosis (VT) (n = 14) and venous thrombosis due to oral contraceptive use (n = 16) in the stable period after the acute thrombotic event. Coagulation and fibrinolytic parameters, as well as classical metabolic variables, were measured and compared with 52 age-matched, healthy controls. In MI women we observed elevated tissue type plasminogen activator (t-PA) antigen levels, which correlated significantly with parameters of the plurimetabolic syndrome. In LACI women we found elevated fibrinogen, which correlated with D-dimer, systolic blood pressure, smoking, and sedimentation rate. Prolonged euglobulin clot lysis time, elevated t-PA antigen, PAI-1 antigen and activity, which all correlated with parameters of the plurimetabolic syndrome, were found in women with idiopathic VT, who were also clearly obese but not in women in whom oral contraceptives were the triggering factor for VT. Our results showed not parallel, but different profiles of alterations in fibrinolytic and coagulation parameters in line with the prediction of a vascular bed specific thrombosis process.