Plasma beta-thromboglobulin and platelet factor 4 concentrations in patients with atrial fibrillation

The clinical significance of beta-thromboglobulin (beta-TG) and platelet factor 4 (PF-4) levels were evaluated in 26 patients with atrial fibrillation (af) complicated by valvular heart disease (VHD), 73 patients with af but without valvular heart disease and 57 normal subjects. The beta-TG level was significantly higher in af patients without VHD than in normal subjects (49.4 +/- 35.8 ng/ml vs 31.2 +/- 14.0 ng/ml, p less than 0.01) and in af patients with VHD than in normals (64.1 +/- 52.8 ng/ml vs 31.2 +/- 14.0 ng/ml, p less than 0.01). Af patients with or without VHD tended to show high levels of PF4 compared with normals (af patients without VHD: 34.1 +/- 45.5 ng/ml, af patients with VHD: 18.6 +/- 27.2 ng/ml, normals: 11.6 +/- 8.2 ng/ml). There was no correlation between beta-TG levels and age in af patients without VHD or in normals. There was also no correlation between beta-TG levels and heart rate in af patients without VHD. The activation of platelets was suggested in patients with atrial fibrillation on the basis of increased levels of platelet releasing substances, especially in those with VHD. The high levels of beta-TG and PF4 in patients with atrial fibrillation may be one explanation for the high incidence of thromboembolism in these patients, indicating the necessity of antiplatelet therapy.     

Platelet activation during thrombolysis and percutaneous transluminal coronary angioplasty in the acute phase of myocardial infarction

To clarify the mechanism of recanalization and reocclusion in thrombolysis and percutaneous transluminal coronary angioplasty (PTCA), the plasma concentrations of beta-thromboglobulin (beta-TG), thromboxane B2 (TXB2) and platelet aggregation adenosine diphosphate (ADP) (2 microM/ml, collagen 2 micrograms/ml) were assessed in 11 normal subjects and in 19 patients with acute myocardial infarction whose infarct-related vessels were recanalized by thrombolysis and/or PTCA. In patients with acute myocardial infarction, the plasma concentrations of beta-TG and TXB2 were significantly higher than those in normal subjects (beta-TG: 128 +/- 132 ng/ml vs 38 +/- 17 ng/ml, TXB2: 131 +/- 154 pg/ml vs 36 +/- 18 pg/ml). Collagen-induced platelet aggregation decreased significantly in patients with acute myocardial infarction; whereas, ADP-induced platelet aggregation showed no significant difference. Infarct-related vessels recanalized by thrombolysis (seven patients: group 1) and PTCA (seven patients: group 2) were patent on the follow-up angiograms. Infarct-related vessels were reoccluded in five patients immediately after PTCA or during the follow-up angiography (group 3). Beta-TG and TXB2 did not change before and after recanalization in groups 1 and 2, but increased significantly after recanalization in group 3 (beta-TG: 155 +/- 185 ng/ml----269 +/- 233 ng/ml, TXB2: 104 +/- 87 pg/ml----169 +/- 91 pg/ml). Platelet aggregation did not differ significantly among the three groups. We concluded that platelets are not activated during thrombolysis and/or PTCA in cases without reocclusion, while platelets are markedly activated during PTCA in cases with reocclusion. Thus, it is suggested that platelet activation plays an important role in the mechanism of reocclusion.     

Increased blood coagulation and platelet activation in patients with infective endocarditis and embolic events

BACKGROUND: Inflammation-induced procoagulant changes and alterations in platelet activity appear to play an important role in thromboembolic complications of infective endocarditis (IE). HYPOTHESIS: The aim of this study was to investigate systemic coagulation activity, fibrinolytic capacity, and platelet activation in patients with IE with and without embolic events by measuring the plasma levels of prothrombin fragment 1+2 (PF1+2), thrombin-antithrombin III complex (TAT), plasminogen activator inhibitor-1 (PAI-1), beta-thromboglobulin (beta-TG), and platelet factor 4 (PF4), respectively. METHODS: The study included 76 consecutive patients (female = 55, male = 21, mean age 26 years, range 8-64 years) with definite IE according to the Duke criteria; of these, 13 (17.1%) had embolic events. RESULTS: Plasma concentrations of PF1+2 (3.2 +/- 1.3 vs. 1.7 +/- 0.7 and 1.4 +/- 0.7 nmol/l, p < 0.001, respectively) and TAT (7.3 +/- 1.5 vs. 2.9 +/- 1.2 and 2.2 +/- 1.1 ng/ml, p < 0.001, respectively) were elevated in patients with embolic events compared with patients without embolic events and control subjects. Similarly, patients with embolic events had increased plasma levels of beta-TG (63.3 +/- 10.9 vs. 33.1 +/- 11.6 and 19.1 +/- 10.6 ng/ml, p < 0.001, respectively) and PF4 (106.0 +/- 28.7 vs. 50.3 +/- 16.7 and 43.0 +/- 15.8 ng/ml, p < 0.001, respectively) compared with those without embolic events and the control group. Embolic patients also had higher PAI-1 levels than nonembolic patients and healthy subjects (14.4 +/- 6.4 vs. 8.6 +/- 5.9 and 5.4 +/- 4.3 ng/ml, p = 0.002, respectively). CONCLUSION: Patients with IE and with subsequent thromboembolism have increased systemic coagulation activation, enhanced platelet activity/damage, and impaired fibrinolysis. The resulting imbalance produces a sustained hypercoagulable state, which contributes to the increased risk of thromboembolic events in this particular group.     

Raised plasma concentrations of platelet factor 4 (PF4) in Crohn's disease.

Plasma platelet factor 4 (PF4), secreted by the platelets, is an index of platelet aggregation and thromboembolic risk. The authors assessed PF4 in 20 patients with Crohn's disease (ileitis in 13 patients, ileocolitis in seven) and in 20 healthy volunteers. Disease activity was low (Crohn's Disease Activity Index less than 150) in 11 patients and high in nine. Radioimmunoassay of PF4 using Abbott's Kit was performed on one sample of plasma from each subject (nv less than or equal to 0.324 nmol/ml), (nv less than or equal to 10 ng/ml). A significantly higher concentration of PF4 was found in Crohn's disease patients: 4.625 +/- 1.1 nmol/ml (142.5 +/- 36 ng/ml) than in the control group: 0.189 +/- 0.07 nmol/ml (5.6 +/- 4.8 ng/ml) (Z = 5.396, p less than 0.0001). No correlation was present between PF4 levels and activity, the site of disease, or medical treatment with or without prednisone.     

The effects of trapidil on left ventricular function and platelet aggregation in patients with coronary artery disease subjected to pacing.

The effects of the intravenous administration of 100 mg of trapidil on systolic and diastolic left ventricular functions and coronary sinus blood flow, as well as on myocardial lactate metabolism and platelet aggregation, were investigated before and after pacing in 12 patients with coronary artery disease. Pacing without administration of trapidil provoked angina in 6 of these patients. During rest, trapidil decreased the mean blood pressure by an average of 5 mmHg (from 112 +/- 15 to 107 +/- 8 mmHg, p less than 0.05) and the left ventricular end-diastolic pressure by an average of 4 mmHg (from 10 +/- 3 to 6 +/- 2 mmHg, p less than 0.05). Trapidil also caused both the max dp/dt and the coronary sinus blood flow to increase slightly, although it had no significant effect on diastolic function, myocardial lactate metabolism, or platelet aggregation. During the pacing that followed trapidil administration, chest pain was not provoked in the same 6 patients who had previously experienced chest pain on pacing. The extent of ST-segment depression also improved from -1.6 +/- 0.3 to -0.9 +/- 0.7 mm (p less than 0.05) and there was a significant suppression of the production of myocardial lactate. When pacing was terminated, trapidil caused a decrease in left ventricular systolic pressure from 173 to 156 mmHg (p less than 0.05), and also caused a decrease of the left ventricular end-diastolic pressure, from 16 +/- 4 to 8 +/- 2 mmHg (p less than 0.05). Trapidil had no significant effect on platelet aggregation activity with either a 1 microM or a 2 microM dose of ADP (adenosine diphosphate). However, the beta-TG level was suppressed, decreasing from 119 +/- 14 to 99 +/- 19 ng/ml in the arterial blood (p less than 0.1) and from 114 +/- 9 to 103 +/- 17 ng/ml (p less than 0.1) in the coronary sinus blood. Reductions in the preload and afterload by trapidil were of far greater magnitude than either its coronary dilatory or positive chronotropic effects in patients with coronary artery disease. Thus trapidil, a new antianginal agent appears to inhibit the production of platelet derived growth factors and may, therefore, protect the arteries from atherosclerosis as it promotes beneficial systemic hemodynamics in patients with depressed ventricular function.     

Increased platelet activity in patients with isolated coronary artery ectasia

BACKGROUND: The common coexistence with coronary artery disease has led to the suggestion that coronary artery ectasia (CAE) is a variant of coronary artery disease. The mechanisms, however, responsible for CAE formation during the atherosclerotic process and the exact clinical significance are not well known. In this study, we aimed to investigate platelet activity in patients with isolated CAE by using specific markers of platelet activation as P-selectin, beta-thromboglobulin (beta-TG) and platelet factor 4 (PF4). METHODS: Thirty-two patients with isolated CAE without significant stenosis and 30 control participants with angiographically normal coronary arteries were included in this study. According to the angiographic definition used in the Coronary Artery Surgery Study, a vessel is considered to be ectasic when its diameter is > or = 1.5 times that of the adjacent normal segment in segmental ectasia. Plasma P-selectin, beta-TG and PF4 levels were measured in all patients and control participants using enzyme-linked immunosorbent assay method. RESULTS: Patients with isolated CAE were detected to have significantly higher levels of plasma P-selectin, beta-TG and PF4 in comparison with control participants with angiographically normal coronary arteries (P-selectin: 248+/-46 vs. 154+/-32 ng/ml, respectively, P<0.001; beta-TG: 51+/-19 vs. 21+/-9 ng/ml, respectively, P<0.001; PF4: 58+/-23 vs. 33+/-11 ng/ml, respectively, P<0.001). CONCLUSION: In conclusion, we have shown for the first time that patients with isolated CAE have raised levels of plasma P-selectin, beta-TG and PF4 compared with control participants with angiographically normal coronary arteries, suggesting increased platelet activation in patients with CAE.     

Augmented platelet reactivity and thromboxane A2 production possible aggravating factors in unstable angina

We examined platelet aggregation and plasma levels of thromboxane B2, a stable metabolite of thromboxane A2, in patients with unstable angina and correlated these platelet indices with the response to antianginal conventional therapy such as isosorbide dinitrate and calcium channel blocker. Eight of 36 patients exhibited anginal attacks more than 5 times/week in spite of the therapy, designated refractory unstable angina, associated with augmented platelet aggregation induced by arachidonate (0.3 mM, 71 +/- 3%, mean +/- SEM) and collagen (2 micrograms/ml, 72 +/- 5%), and elevated plasma levels of thromboxane B2 (350 +/- 19 pg/ml). In the remainder of the patients whose anginal attacks were effectively subsided by the therapy, platelet aggregation was much lower (arachidonate: 34 +/- 9%, collagen: 31 +/- 8%, p less than 0.01) and plasma levels of thromboxane B2 were also lower (295 +/- 12 pg/ml, p less than 0.05). To evaluate the effect of selective thromboxane A2 blockade on clinical findings and platelet reactivity in refractory unstable angina, OKY-046 (600 mg/day, p.o.) was administered to another 14 patients with refractory unstable angina in addition to the conventional therapy. We found that platelet aggregation induced by arachidonate (71 +/- 4%) and collagen 65 +/- 8%) was markedly reduced (44 +/- 7% and 24 +/- 3%, respectively, p less than 0.01) and plasma levels of thromboxane B2 (358 +/- 31 pg/ml) and thromboxane B2 production in serum (29 +/- 5 ng/ml) were also significantly reduced after OKY-046 treatment (262 +/- 21 pg/ml, p less than 0.05, and 1.4 +/- 0.2 ng/ml, p less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)     

Fibrinopeptide A and platelet factor levels in unstable angina pectoris

Fibrinopeptide A, platelet factor 4, beta-thromboglobulin, thromboxane B2, and 6-keto-prostaglandin F1 alpha were estimated by radioimmunoassay on venous plasma samples taken within 48 hr of admission from 16 consecutive patients with unstable angina and 15 patients with stable angina matched for clinical variables. The ratio of circulating platelet aggregates, platelet aggregation to increasing concentrations of ADP (0.455 to 1.82 micrograms/ml), and platelet thromboxane B2 production in vitro were also tested. The two groups of patients were statistically similar in terms of sex distribution, age, presence of risk factors, use of medication, extent of coronary artery disease and history of previous myocardial infarction. Mean plasma levels of fibrinopeptide A were 2.7 +/- 0.4 ng/ml (geometric means +/- SEM, range 1.5 to 5.5) in patients with stable angina vs 5.5 +/- 1.8 ng/ml (range 2.4 to 32; p less than .001) in those with unstable angina. In the latter group, after 6 to 8 days, fibrinopeptide A levels decreased to 3.6 +/- 0.5 ng/ml (range 1.5 to 9.3; p less than .04 vs admission). All other variables measured were statistically identical in the two groups. We conclude that plasma fibrinopeptide A levels, as opposed to platelet factors, discriminate between patients with unstable and stable angina, indicating an activation of the coagulation system in unstable angina.     

Evidence that platelet density depends on the alpha-granule content in platelets

The relation between platelet buoyant density and beta-thromboglobulin (beta-TG), a marker for platelet alpha-granule content, was assessed by three independent approaches. (1) Platelets were separated on iso- osmolar discontinuous Stractan density gradients into five fractions, ranging in density from 1.061 g/ml to 1.091 g/ml (20 degrees C). The beta-TG content (mean +/- SD, n = 17) increased with the platelet density from 27.8 +/- 8.6 micrograms beta-TG/10(9) cells (20% less- dense platelets) up to 65.6 +/- 15.5 micrograms beta-TG/10(9) cells (15% most-dense platelets). (2) Activation of platelets in platelet- rich plasma with thrombin, adenosine diphosphate, collagen, or epinephrine resulted in a decreased density of the platelets. This was only seen when there was simultaneous secretion of beta-TG. (3) The less-dense and the more-dense platelet fractions, after isolation by density gradient centrifugation, were separately treated with thrombin. After complete degranulation, the density distribution of the originally less-dense and more-dense platelets were identical and were much narrower than the density distribution of resting platelets.     

Plasma levels of beta-thromboglobulin and platelet factor 4 in relation to the venous platelet concentration

The plasma levels of beta-thromboglobulin (beta-TG) and platelet factor 4 (PF-4) were determined in patients with various hematologic malignancies, and the results were related to simultaneously determined venous platelet counts. All studied patients were in a steady state. The plasma beta-TG concentrations were determined on 69 occasions and the values ranged from 0 to 82 ng/ml. In 33 instances, the venous platelet count was <25 x 10 (9/1) and in two thirds of these samples beta-TG was undedectable. The highest values for plasma beta-TG were found in patients with the highest venous platelet counts. A highly significant correlation (r=0.77, p <0.001) between the values for plasma beta-TG and venous platelet count was present. The plasma concentrations for PF-4 ranged from 0 to 50 ng/ml. Similarly, there was a highly significant relationship (r=0.78, p<0.001) between the values for PF-4 and venous platelet concentration. We conclude, if the plasma levels of beta-TG and PF-4 are used as markers of platelet activation in vivo, it is necessary to simultaneously consider the platelet concentration in the collected blood.     

Plasma beta-thromboglobulin values in thrombocytopenic patients with acute leukemia

Plasma beta-thromboglobulin (beta-TG) levels were measured in 14 healthy subjects and in 20 acute leukemia (AL) patients, newly diagnosed, with highly variable values for venous platelet counts. For healthy subjects the plasma beta-TG levels ranged 12-38 (mean 17) ng/ml. In this group of patients with AL, a highly significant positive correlation (P < 0.001) between the values for plasma beta-TG and venous platelet count was present. During a thrombocytopenic period, the plasma beta-TG concentraton was measured in nine of the AL patients immediately before and 10 to 12 hours after platelet transfusion therapy. Fourteen platelet transfusions were administered when the patient's highest temperature of the day was < 38.5 degrees C, and 18 when the highest temperature of the day was greater than or equal to 38.5 degrees C. The mean pre-transfusion and post-transfusion beta-TG values for the 14 platelet transfusions were 7 +/- 2 and 20 +/- 5 ng/ml, respectively. The corresponding means for the 18 transfusions given to febrile patients were 5 +/- 2 ng/ml and 11 +/- 2 ng/ml, respectively. Of the pretransfusion values, 11/14 and 14/18 were below the control range. We conclude that the plasma beta-TG values are considerably lower in thrombocytopenic patients than in subjects with normal platelet counts. Further work should provide reference values for plasma beta-TG over a wide range of venous platelet counts.     

Platelet aggregation and thromboxane A2 production after adrenergic stimulation in young healthy humans

The effects of adrenergic stimulation on platelet aggregation (platelet aggregation ratio; PAR), beta-thromboglobulin (beta-TG) release and plasma thromboxane B2 (TxB2) levels were investigated in 25 healthy young volunteers. Adrenergic stimulation induced by cold application was checked by evaluating the changes in the calculated vascular resistance in the forearm. A prompt increase in platelet aggregates and plasma beta-TG and TxB2 concentrations was observed after adrenergic stimulation. PAR changed from resting values of 0.97 +/- 0.05 to 0.75 +/- 0.08 (p less than 0.001) at the end of cold application. At the same time, beta-TG plasma concentration increased from 32.09 +/- 19.64 to 135.48 +/- 37.97 ng/ml (p less than 0.001) and TxB2 plasma levels changed from 0.49 +/- 0.24 to 0.99 +/- 0.39 pmol/ml (p less than 0.001). TxB2 levels, but not PAR and beta-TG concentration came back to the resting values at the end of the observation period (10 min). Aspirin, as the lysine acetylsalicylate equivalent to 5 mg/kg i.v. of acetylsalicylic acid, although able to completely inhibit platelet cyclooxygenase failed to inhibit the plasma TxB2 increase induced by adrenergic stimulation. This strongly suggests that the increase in plasma TxB2 following adrenergic stimulation is of extraplatelet origin. Also beta-TG and PAR changes were not affected by aspirin administration.     

Selective decrease in platelet dense granule adenine nucleotides during recovery from acute experimental thrombocytopenia and ensuing thrombocytosis in baboons

Serial measurements of platelet volume, platelet content of adenine nucleotides, beta-thromboglobulin (beta-TG), platelet factor 4 (PF4) and ex vivo platelet aggregation were made in baboons under basal, steady-state conditions of normal platelet production, and during recovery from acute thrombocytopenia induced by the exposure of flowing blood to spherical glass microbeads. The mean basal platelet count of 509 +/- 107 X 10(9)/l (+/- 1 SD; n = 4) fell acutely to 36.8 +/- 12.6 X 10(9)/l after the insertion of glass bead columns and blood filters, placed distally, for 60 min into surgically implanted arteriovenous-shunts in heparinized baboons. After the irreversible removal of up to 90% of the baseline circulating platelet population, recovery from thrombocytopenia was characterized by a constant rate of increase in circulating platelet counts (115 +/- 11 X 10(9)/l/d) and a rebound thrombocytosis to 1.5 times the basal platelet count after 7 d. Steadystate thrombocytopoiesis was achieved by 3-4 weeks after the onset of thrombocytopenia. Platelet dense granule ADP and ATP decreased significantly from 3.89 +/- 0.20 and 2.33 +/- 0.25 mumol/10(11) platelets respectively at baseline to 2.17 +/- 0.37 and 1.68 +/- 0.37 mumol/10(11) platelets respectively after 7 d (P less than 0.001 in both cases) and normalization was achieved only after 4 weeks. By contrast, the mean platelet volume and platelet content of beta-TG and PF4 did not change significantly throughout the course of study (P greater than 0.1 in both cases). Platelet function, assessed by platelet aggregation ex vivo, demonstrated that platelet function was not impaired despite the significant decrease in dense granule ADP. We conclude that a selective, temporal reduction in platelet dense granule adenine nucleotides reflects changes in the thrombocytopoietic control mechanism secondary to induction of acute thrombocytopenia.     

Effects of varying dietary fatty acid ratios on plasma lipids and platelet function in the African green monkey

The influence of varying dietary fatty acid ratios on plasma lipids, platelet function and the potential for thrombosis was evaluated in the African green monkey (Cercopithecus aethiops), an animal model widely used in cardiovascular research. Ten adult animals, 5 males and 5 females, at intervals of 2 months, were fed a series of 7 diets with fatty acid ratios (P:S) ranging from 3:1 to 1:4. Platelet aggregation in vitro, plasma levels of beta-thromboglobulin and platelet factor 4, platelet membrane fatty acid composition and plasma lipids including total cholesterol, HDL and LDL were monitored at the end of each dietary period. Platelet hypersensitivity to ADP aggregation (3 and 10 microM) and plasma beta-thromboglobulin were elevated in both males and females when dietary P:S exceeded 1.5:1 (beta-TG = 45 ng/ml) as compared to control diets either reflecting current North American or that recommended as a desirable dietary goal (P:S = 1:1, beta-TG = 10 ng/ml). Diets enriched in saturated fatty acids (P:S = 1:2) also altered platelet function, but the effects were most consistently observed in female animals (beta-TG = 32 ng/ml). Platelet hypersensitivity was lost and beta-TG levels were at baseline when the animals were returned to the control diets. Platelet sensitivity did not correlate with membrane composition which generally reflected dietary composition. Both the saturated and the polyunsaturated fatty acid enriched diets lowered plasma HDL levels, and the saturated fatty acid diets elevated plasma LDL.(ABSTRACT TRUNCATED AT 250 WORDS)     

Nutritional zinc increases platelet reactivity

After ingestion of 220 mg zinc sulfate, platelet aggregation was evaluated at various time intervals (i.e., T = 0, 1, and 3 hr) and the autologous plasma analyzed by atomic absorption analysis. The zinc levels increased maximally some 0.4 +/- 0.2 microgram/ml within 3 hr after ingestion, which for the entire blood pool corresponds to only 5% of the ingested zinc. Aggregation responses of platelet rich plasma (PRP), instigated with suboptimal levels of thrombin (less than 0.2 U/ml), ADP (less than 2 microM), epinephrine (less than 2 microM), collagen (less than 2 micrograms/ml), or PAF (less than 50 ng/ml), show significant improvement to at least one aggregant. Mean +/- SEM values for delta % aggregation increase are as follows: thrombin, 51 +/- 10%; epinephrine, 21 +/- 6%; ADP, 31 +/- 6%; collagen 23 +/- 6%; and platelet aggregating factor (PAF), 56 +/- 6%. For controls, the platelets from one individual with Glanzmann thrombasthenia as well as four undosed volunteers exhibited no significant changes in platelet responsiveness. Increased platelet responsiveness to agonists after zinc sulfate ingestion was observed in PRP from blood collected in either citrate or heparin. We demonstrate that within a relatively short time period, single bolus of nutritional zinc intake can significantly increase platelet reactivity. These findings show that nutritional zinc availability is relevant to hemostasis and may pertain to the viability of platelet concentrates in blood banks.     

Comparison of platelet function during exercise in normal subjects and coronary artery disease patients: Potential role of platelet activation in myocardial ischemia

Platelet function parameters as influenced by exercise stress were evaluated in 22 patients with coronary artery disease (CAD) and in 13 normal subjects. Upon exercise stress, 14 CAD patients exhibited positive tests and eight exhibited negative tests. Platelet counts during exercise increased similarly in normal and CAD patients. Platelet aggregation response to ADP was unaffected by exercise both in normal and CAD patients. Platelets from 7 of the 14 CAD patients with positive stress tests had increased sensitivity to endoperoxide analog (U-46619) defined as less than 200 ng/ml U-46619 required for 50% platelet aggregation. Resting plasma beta-thromboglobulin (B-TG) levels, an index of in vivo platelet activation, were significantly higher in CAD patients compared to normal subjects (74 +/- 7 and 41 +/- 5 ng/ml, respectively; p less than 0.02). During exercise plasma B-TG levels increased in normal subjects to 60 +/- 5 ng/ml. In contrast, B-TG levels increased to 102 +/- 14 ng/ml in CAD patients (p less than 0.01 compared to normal subjects). These increases were transient and B-TG declined to preexercise values soon after exercise. Eleven of the 12 CAD patients with positive exercise stress tests had increases in plasma B-TG levels, whereas only three of the eight CAD patients with negative stress tests had any increase. These observations of increased platelet activation in certain CAD patients during exercise may be related to exercise-induced myocardial ischemia.     

Comparison of the effects of cellulose triacetate and polysulfone membrane on GPIIb/IIIa and platelet activation

BACKGROUND: During hemodialysis session, several adverse reactions can occur on platelets, which are attributable to bioincompatibility of the dialysis membrane. Glycoprotein IIb/IIIa (GPIIb/IIIa) is the receptor for fibrinogen, which mediates platelet aggregation and adhesion. Accordingly, we compared the influence of a cellulose triacetate (CTA) and polysulfone (PS) membrane on GPIIb/IIIa and platelet activation. METHODS: Blood samples from 5 patients on hemodialysis were taken at 0 time, 15 min, 30 min, 60 min and 240 min, during a single hemodialysis session, by a crossover design using CTA or PS. Platelet count and plasma concentration of GPIIb/IIIa, beta-thromboglobulin (beta-TG) and platelet factor 4 (PF-4) were measured. GPIIb/IIIa was measured by flow cytometry. beta-TG and PF-4 were measured by ELISA. RESULTS: There was no significant change in the total amount of GPIIb/IIIa during dialysis session between the CTA and PS. However, the level of bound GPIIb/IIIa was significantly (p < 0.0002) increased from 1,426 +/- 435 to 40,446 +/- 2,777 mol/PLT with PS. In contrast, there was no significant change with CTA (3,258 +/- 1,469 to 4,301 +/- 1,422 mol/PLT). The platelet counts and beta-TG and PF-4 behavior during the dialysis session did not show significant change between the PS and CTA. CONCLUSION: The characterization of changes in platelet membrane receptor (GPIIb/IIIa) may be a useful marker for studying the biocompatibility of dialysis membranes. On platelet aggregation, CTA might be more biocompatible membrane than PS.     

Heparin-releasable platelet factor 4 in patients with coronary artery disease.

Recently, platelet factor 4 (PF4) release by heparin (heparin-releasable PF4) has been examined as a useful marker of the interaction between the substances liberated from circulating platelets and the vascular endothelium. We compared the plasma levels of PF4 and beta-thromboglobulin (beta-TG) after intravenous heparin injection in patients with coronary artery disease (CAD) and normal control subjects. We also studied the effects of low-dose aspirin (81 mg/day) on the plasma level of heparin-releasable PF4 in the CAD patients. Blood samples were obtained before and 5 min after the intravenous injection of heparin (1,000 IU) from 23 patients with CAD and 15 normal control subjects. Although the plasma beta-TG level remained unchanged after heparin injection, the plasma PF4 level markedly increased in both groups. There was a significant difference in plasma PF4 levels at 5 min after heparin injection between the CAD group (100.1 +/- 38.1) and the control group (61.0 +/- 24.0) (p less than 0.01). The PF4/beta-TG ratio after heparin injection was also higher in the CAD group than in the control group (p less than 0.01). There was a correlation between the PF4/beta-TG ratio after heparin and the Gensini CAD score, which defines the severity of coronary atherosclerosis (r = 0.489, n = 23, p less than 0.01). Low-dose aspirin was administered to 11 CAD patients for 246.0 +/- 28.8 days. Blood samples for the assay of PF4 and beta-TG were obtained as stated above, and platelet aggregation, thromboxane B2 (TxB2), and 6-keto-prostaglandin F1 alpha (6-keto-PGF1 alpha) levels were also measured before and during aspirin administration.(ABSTRACT TRUNCATED AT 250 WORDS)     

Oxidized low density lipoprotein (LDL) and platelet intracellular calcium: interaction with nitric oxide

The present study tested the effects of ox-low density lipoprotein (LDL) on nitric oxide (NO)-dependent decrease in agonist-stimulated [Ca2+]i. The effects of ox-LDL on platelet aggregation were also evaluated. Platelets loaded with FURA 2 AM (2 micromol/litre) were incubated with NO-donors for 2-10 min to obtain a 40-50% reduction in \[Ca2+]i and with NO-donors plus ox-LDL (100 microg of protein/ml). Thrombin (0.03 U/ml) was used as an agonist. In some experiments 8-Br-cGMP (0.5-1 mmol/l) was used to investigate the NO-dependent intraplatelet signalling system. Slightly oxidized LDL was obtained by leaving native LDL in the light at room temperature for at least 7 days. Ox-LDL did not cause any increase in thrombin-induced [Ca2+] (control: 215.4 +/- 44.3 nmol/l, ox-LDL 223.4 +/- 35.3 nmol/l, M +/- SEM; n = 8) and platelet aggregation (control: 78.7 +/- 4.9% , ox-LDL: 78.9 +/- 4.2% , n = 12). Ox-LDL antagonized the effects of NO-donors on platelet [Ca2+]i (NO-donor: 137.4 +/- 22.1 nmol/l, NO + ox-LDL: 177.3 +/- 27.6 nmol/l, n = 11; P < 0.001) and platelet aggregation (NO-donor: 15.4 +/- 3.4% , NO + ox-LDL: 28.9 +/- 3.8%, n = 24; P < 0.001). Ox-LDL did not affect the inhibitory activities of 8-Br-cGMP on platelet aggregation (8-Br-cGMP: 22.0 +/- 8.5%, 8-Br-cGMP + ox-LDL: 19.3 +/- 7.8%, n = 5) and platelet [Ca2+]i . In conclusion, slightly oxidized LDL does not directly activate platelets and does not i affect the intracellular NO-dependent signalling system. The present results suggest that LDL reduces the antiplatelet activity of NO mainly by preventing its biological effects.     

Effect of infective endocarditis on blood coagulation and platelet activation and comparison of patients with to those without embolic events

Inflammation-induced procoagulant changes and alterations in platelet activity appear to play an important role in thromboembolic complications of infective endocarditis (IE). The aim of this study was to investigate systemic coagulation activity, fibrinolytic capacity, and platelet activation in IE patients with and without embolic events by measuring the plasma levels of prothrombin fragment 1 + 2, thrombin-antithrombin III complex, plasminogen activator inhibitor-1, beta-thromboglobulin, and platelet factor 4. The study included 76 consecutive patients with definite IE according to the Duke criteria. Among them, 13 (17.1%) had major embolic events. Plasma concentrations of prothrombin fragment 1 + 2 (3.2 +/- 1.3 vs 1.7 +/- 0.7 and 1.4 +/- 0.7 nmol/L, p <0.001, respectively) and thrombin-antithrombin (7.3 +/- 1.5 vs 2.9 +/- 1.2 and 2.2 +/- 1.1 ng/ml, p <0.001, respectively) were elevated in patients with embolic events compared with both patients without embolic events and control subjects. Similarly, patients with embolic events had increased plasma levels of beta-thromboglobulin (63.3 +/- 10.9 vs 33.1 +/- 11.6 and 19.1 +/- 10.6 ng/ml, p <0.001, respectively) and platelet factor 4 (106.0 +/- 28.7 vs 50.3 +/- 16.7 and 43.0 +/- 15.8 ng/ml, p <0.001, respectively) compared with those without embolic events and the control group. Embolic patients also had higher plasminogen activator inhibitor-1 levels than both nonembolic patients and healthy subjects (14.4 +/- 6.4 vs 8.6 +/- 5.9 and 5.4 +/- 4.3 ng/ml, p = 0.002, respectively). In conclusion, IE patients with subsequent thromboembolism have increased systemic coagulation activation, enhanced platelet activity/damage, and impaired fibrinolysis. The resulting imbalance produces a sustained hypercoagulable state that may contribute to the increased risk of thromboembolic events in this particular group.