thromboxane-b2 and Hemorrhagic-Disorders

Recombinant human erythropoietin may improve hemostasis of uremic patients by correcting anemia. However, a complete correction of renal anemia carries the risk of hypertension, encephalopathy, thrombosis, and hyperkalemia. Our aim was to establish the minimum level of packed cell volume (PCV) achieved with recombinant human erythropoietin that corrects the prolonged bleeding time in uremia. Twenty patients with chronic renal failure, anemia, and very prolonged bleeding time (greater than or equal to 15 minutes) were randomly allocated to erythropoietin or no specific treatment. The initial dose of erythropoietin was 50 U/kg intravenously (IV) three times a week. Every 4 weeks, the dose was increased by 25 U/kg until a normalization of bleeding time was achieved. Erythropoietin at a dose ranging from 150 to 300 U/kg/wk induced an increase in PCV to a range of 27% to 32% in all patients but one, and normalized bleeding time in all patients. A significant negative correlation (r = 0.898, P less than 0.001) was found between PCV and bleeding time measurements. Erythropoietin also significantly (P less than 0.01) increased values for red blood cell (RBC) distribution width (basal, 11.3 +/- 0.6; 12 weeks, 13.1 +/- 1.3). Platelet count and platelet function parameters did not significantly change. In untreated patients, no changes were recorded in all the parameters considered. These results establish in a controlled fashion that erythropoietin shortens bleeding time of uremic patients and indicate that a partial correction of renal anemia is enough to normalize bleeding time.

Topics: Adult; Aged; Bleeding Time; Erythropoietin; Female; Hematocrit; Hemorrhagic Disorders; Humans; Male; Middle Aged; Platelet Count; Prothrombin Time; Recombinant Proteins; Thromboxane B2; Uremia

The survival of fresh and preserved platelets has been used primarily to determine their therapeutic effectiveness. The function of the fresh and preserved platelets has been difficult to assess. In stable thrombocytopenic patients, platelet function of fresh and preserved allogeneic platelets is evaluated by the reduction in bleeding time. In this study of healthy male baboons, both the survival and function of autologous fresh, liquid-preserved, and cryopreserved platelets in the correction of an aspirin-induced thrombocytopathy was evaluated.. Five healthy male baboons were studied on eight occasions over a 4-year period. To produce a prolonged bleeding time, the baboon was administered 325 mg of aspirin 18 hours before receiving autologous transfusion. The fresh, liquid-preserved, and previously frozen washed platelets were labeled with (111)In-oxine before autologous transfusion. The autologous, nonaspirinated platelets' ability to reduce the aspirin-induced prolonged bleeding time and increase the shed blood thromboxane B2 level at the template bleeding time site was studied.. Platelets stored at 22 degrees C for 48 hours had in vivo recovery values similar to those platelets stored for 18 hours, and they significantly reduced the bleeding time and increased the shed blood thromboxane level after transfusion. Platelets stored at 22 degrees C for 72 hours had in vivo recovery values similar to those platelets stored for 18 hours, but the bleeding time was not corrected after transfusion, although there was a significant increase in the shed blood thromboxane B2 level. The cryopreserved platelets significantly reduced the bleeding time and significantly increased the shed blood thromboxane level after transfusion. Cryopreserved platelets had better in vivo survival and function than the 5-day liquid-stored platelets.. The survival of autologous fresh, liquid-preserved, or cryopreserved platelets did not correlate with their function to reduce an increased bleeding time in baboons treated with aspirin.

Topics: Animals; Aspirin; Bleeding Time; Blood Platelets; Blood Preservation; Blood Transfusion, Autologous; Cell Survival; Citric Acid; Cryopreservation; Glucose; Hemorrhagic Disorders; Hemostasis; Male; Papio; Platelet Count; Platelet Transfusion; Solutions; Species Specificity; Temperature; Thromboxane B2; Time Factors

In this study, gram-positive Staphylococcus aureus lipoteichoic acid (LTA) dose-dependently (0.1-1.0 microg/ml) and time-dependently (10-60 min) inhibited platelet aggregation in human platelets stimulated by agonists. LTA also dose-dependently inhibited phosphoinositide breakdown and intracellular Ca+2 mobilization in human platelets stimulated by collagen. LTA (0.5 and 1.0 microg/ml) also significantly inhibited thromboxane A2 formation stimulated by collagen in human platelets. Moreover, LTA (0.1-1.0 microg/ml) dose-dependently decreased the fluorescence of platelet membranes tagged with diphenylhexatrience. Rapid phosphorylation of a platelet protein of Mr. 47,000 (P47), a marker of protein kinase C activation, was triggered by PDBu (30 nM). This phosphorylation was markedly inhibited by LTA (0.5 and 1.0 microg/ml) within a 10-min incubation period. These results indicate that the antiplatelet activity of LTA may be involved in the following pathways: LTA's effects may initially be due to induction of conformational changes in the platelet membrane, leading to a change in the activity of phospholipase C, and subsequent inhibition of phosphoinositide breakdown and thromboxane A2 formation, thereby leading to inhibition of both intracellular Ca+2 mobilization and phosphorylation of P47 protein. Therefore, LTA-mediated alteration of platelet function may contribute to bleeding diathesis in gram-positive septicemic and endotoxemic patients.

Topics: Calcium Signaling; Cell Membrane; Collagen; Cytosol; Dose-Response Relationship, Drug; Endotoxemia; Enzyme Activation; Gram-Negative Bacterial Infections; Gram-Positive Bacterial Infections; Hemorrhagic Disorders; Humans; L-Lactate Dehydrogenase; Lipopolysaccharides; Membrane Fluidity; Membrane Lipids; Nitric Oxide Synthase; Nitric Oxide Synthase Type II; Peptides; Phorbol 12,13-Dibutyrate; Phosphatidylinositols; Phosphorylation; Platelet Aggregation; Platelet Aggregation Inhibitors; Platelet Glycoprotein GPIIb-IIIa Complex; Protein Kinase C; Protein Processing, Post-Translational; Sepsis; Shock, Septic; Staphylococcus aureus; Teichoic Acids; Thromboxane A2; Thromboxane B2

We encountered a patient with congenital platelet cyclo-oxygenase deficiency with normal ability to synthesize vascular prostaglandin I2 (PGI2) and thromboxane A2 (TXA2). The patient's peripheral blood monocytes did not show cyclo-oxygenase (COX) activity, but cultured bone marrow fibroblasts showed COX activity. To determine the mechanism of primary hemostasis in this patient, we examined the effect of oral administration of aspirin (1 g) on bleeding time and thromboxane B2 (TXB2), 6-keto prostaglandin F1 alpha (6-keto-PGF1 alpha) production in the blood emerging from the incision in this patient. The bleeding time was markedly prolonged by the administration of aspirin, and this prolongation was associated with the inhibition of TXB2 in the effluent blood, which seemed to be derived from the vessel wall. These findings suggest that vascular TXA2 production plays an important role in the maintenance of hemostasis.

Topics: 6-Ketoprostaglandin F1 alpha; Administration, Oral; Adult; Arteries; Aspirin; Bleeding Time; Blood Platelets; Bone Marrow; Cyclooxygenase Inhibitors; Endothelium, Vascular; Epoprostenol; Female; Fibroblasts; Hemorrhagic Disorders; Humans; Isoenzymes; Monocytes; Platelet Aggregation Inhibitors; Prostaglandin-Endoperoxide Synthases; Thromboxane B2; Uterus

Haemorrhagic diatheses due to platelet function defects are a heterogenous and poorly understood group of conditions. We report the investigation of a female with a lifelong history of epistaxes, haemarthroses, menorrhagia and persistent iron-deficiency anaemia. Although platelet numbers and morphology were normal, platelet function was abnormal both in vivo and in vitro. Skin bleeding time was prolonged and aggregation thresholds in platelet-rich plasma to a variety of weak and strong agonists were increased. Platelet granule contents were normal and membrane glycoproteins GpIb and GpIIIa were present in normal amounts. Polyphosphoinositide metabolism and phosphatidic acid generation were diminished in thrombin-stimulated platelets, as was phosphorylation of the 47 kD substrate for protein kinase C and the 20 kD protein myosin light chain kinase, indicating impaired generation of the intracellular second messengers diacylglycerol and inositol trisphosphate due to diminished stimulated phospholipase C activity. Although intracellular free calcium, calmodulin activity and basal cAMP concentrations were normal, washed platelets showed increased cAMP accumulation following stimulation with prostaglandin E1 and forskolin. Platelet membrane lipid analysis revealed a reduction in plasmalogen phosphatidylethanolamine content. It is suggested that the membrane phospholipid abnormalities cause the abnormal platelet reactivity by interfering with signal transduction from platelet receptor, via intermediary G proteins, to phospholipase C and adenylate cylase. The bleeding tendency is likely to be a consequence of the altered stimulus-response coupling.

Topics: Blood Platelet Disorders; Blood Platelets; Calcium; Calmodulin; Female; Hemorrhagic Disorders; Humans; Membrane Lipids; Middle Aged; Phosphatidylinositols; Phospholipids; Phosphorylation; Platelet Aggregation; Signal Transduction; Thromboxane B2

Platelet aggregation, secretion of serotonin, and formation of thromboxane B2 induced by platelet-activating factor (1-O-alkyl-2-acetyl-sn-glyceryl-3-phosphorylcholine) were studied in plasma containing physiological concentrations of ionized calcium in eight alcoholics after cessation of heavy drinking. Responses of platelets of four nonalcoholic volunteers, matched with a subgroup of the alcoholics by age and sex, were also investigated. Aggregation of platelets from alcoholics was significantly less throughout the 6-day detoxification period compared with controls. Secretion of serotonin (5-hydroxy-tryptamine) was negligible and the production of thromboxane B2 was not detectable. Decreased platelet aggregability in response to aggregating agents, including platelet-activating factor, may be important in the development of hemorrhagic complications in alcoholics.

Topics: Adult; Aged; Alcoholism; Blood Platelets; Calcium; Ethanol; Female; Hemorrhagic Disorders; Humans; Male; Middle Aged; Platelet Activating Factor; Platelet Aggregation; Serotonin; Smoking; Stimulation, Chemical; Substance Withdrawal Syndrome; Thromboxane B2

The authors describe a patient with a longstanding bleeding disorder associated with impaired platelet aggregation and secretion despite normal granule contents. Thrombin-induced platelet thromboxane A2 production, measured using a radioimmunoassay for thromboxane B2, was markedly decreased or undetectable in platelet-rich plasma and whole blood serum. However, significant amounts of thromboxane B2 were detected on thrombin stimulation of platelets suspended in albumin-free salt medium. Malondialdehyde and 14C-hydroxyheptadecatrienoic acid production was undetectable in the patient's platelets. Liberation of free 14C-arachidonic acid from phospholipids during stimulation of prelabeled platelets was normal, indicating normal phospholipase activity. These observations indicate an albumin-dependent partial deficiency in thromboxane production resulting from a defect either in cyclooxygenase or thromboxane synthetase. Further, the authors studied the effect of albumin on arachidonic acid metabolism in normal platelets. These studies indicate that albumin enhances liberation of arachidonic acid from phospholipids but has an overall inhibitory effect on thromboxane synthesis.

Topics: Adult; Albumins; Arachidonic Acid; Arachidonic Acids; Bleeding Time; Blood Platelet Disorders; Blood Platelets; Chromatography, Gel; Female; Hemorrhagic Disorders; Humans; Malondialdehyde; Partial Thromboplastin Time; Phospholipids; Platelet Aggregation; Platelet Count; Serotonin; Thrombin; Thromboxane A2; Thromboxane B2; Thromboxanes