ristocetin and Uremia

Topics: Adenosine Diphosphate; Adenosine Triphosphate; Anemia, Megaloblastic; Anti-Inflammatory Agents; Blood Coagulation Disorders; Blood Coagulation Tests; Blood Platelet Disorders; Blood Platelets; Carbenicillin; Collagen; Epinephrine; Hemorrhage; Humans; Isoantibodies; Leukemia; Myeloproliferative Disorders; Platelet Aggregation; Postoperative Complications; Purpura, Thrombocytopenic; Ristocetin; Stress, Psychological; Uremia; von Willebrand Diseases

Topics: Actins; Adenosine Diphosphate; Adult; Aged; Arachidonic Acid; Collagen; Cytoskeleton; Epinephrine; Female; Humans; In Vitro Techniques; Kidney Transplantation; Male; Middle Aged; Platelet Aggregation; Renal Dialysis; Ristocetin; Uremia

Using the Born method, based on light transmission in platelet rich plasma, the minimum effective concentration (threshold values) of several platelet agonists for inducing maximum platelet aggregation was determined in healthy dogs. The final concentrations of aggregation agonists were as follows: adenosine diphosphate (ADP) (0.5-50 micromol/L; n = 75 healthy dogs), collagen (0.5-20 mg/mL; n = 75), thrombin (0.1-5 IU/mL; n = 75), ristocetin (1-10 mg/mL; n = 10), and epinephrine (5-50 micromol/L; n = 10). Reference values for maximum aggregation with a lower limit of > 80% were achieved for agonist concentrations 25 micromol/L ADP (80-98%), > or = 10 microg/mL collagen (80-96%), and > or = 1 IU/mL thrombin (80-97%). None of the concentrations of epinephrine and ristocetin used in this study induced quantitative aggregation in the whole group of healthy dogs. We also studied platelet aggregation in 14 uraemic dogs using selected concentrations of aggregation agonists. Aggregation was significantly decreased in uraemic dogs using intermediate agonist concentrations, i.e., in the region of the threshold concentration. In contrast, maximum aggregation was increased in uraemic patients compared to reference values using low concentrations of all three agonists (ADP: 1 micromol/L, collagen: 1 microg/mL, and thrombin: 0.1, 0.2 IU/mL).

Topics: Adenosine Diphosphate; Animals; Blood Platelets; Collagen; Dog Diseases; Dogs; Epinephrine; Female; Hemostatics; Male; Platelet Aggregation; Reference Values; Ristocetin; Thrombin; Uremia

Topics: Adenosine Diphosphate; Arachidonic Acid; Collagen; Humans; Immunosuppressive Agents; In Vitro Techniques; Kidney Failure, Chronic; Mycophenolic Acid; Platelet Aggregation; Ristocetin; Uremia

A bleeding diathesis caused by platelet dysfunction is a major cause of morbidity and mortality in patients with uremia. Platelet adhesion to vascular subendothelium is defective in uremia and depends on the interactions of the platelet glycoprotein (GP) Ib/IX complex with the vascular wall. We measured levels of platelet surface GPIb, platelet surface GPIX, plasma glycocalicin (a product of enzymatic cleavage of GPIb), and ristocetin-induced platelet agglutination (RIPA) in patients undergoing chronic hemodialysis compared with patients undergoing peritoneal dialysis and healthy controls. Patients undergoing chronic maintenance hemodialysis have higher levels of platelet surface expression of GPIb (187+/-10 fluorescent units; P < 0.001) than either healthy controls (120+/-4 fluorescent units; P < 0.001) or patients undergoing peritoneal dialysis (127+/-5 fluorescent units; P < 0.001). Similar changes were observed in platelet surface GPIX. Plasma glycocalicin levels were elevated in chronic hemodialysis patients (71+/-5 nmol/L) compared with healthy controls (36+/-3 nmol/L; P < 0.001). Plasma glycocalicin levels also increased progressively throughout the hemodialysis procedure. The slope of RIPA was significantly lower in chronic hemodialysis patients (46+/-3) than in either healthy controls (67+/-4; P < 0.05) or peritoneal dialysis patients (62+/-2; P < 0.05). In conclusion, patients undergoing chronic maintenance hemodialysis have increased plasma glycocalicin levels and decreased RIPA, which may contribute to diminished platelet adhesion to vascular subendothelium and increased bleeding associated with uremia.

Topics: Blood Platelets; Case-Control Studies; Humans; Peritoneal Dialysis; Platelet Aggregation; Platelet Aggregation Inhibitors; Platelet Glycoprotein GPIb-IX Complex; Renal Dialysis; Ristocetin; Uremia

Erythropoietin treatment is known to correct anemia and to improve hemostasis. Since platelets may contribute to thromboembolic complications, we assessed platelet aggregation in whole blood and platelet-rich plasma from chronically hemodialyzed patients treated with erythropoietin and evaluated in vitro effects of this drug on aggregatory responses of uremic and normal platelets. Recombinant human erythropoietin was given to uremic patients at a dose of 2,000 IU subcutaneously three times a week. Platelet aggregation in whole blood and platelet-rich plasma was induced by collagen, ADP, arachidonic acid, and ristocetin. In uremic patients, erythropoietin therapy resulted in an enhancement of platelet sensitivity to various agonists, particularly in platelet-rich plasma, reaching values comparable to those of healthy volunteers. In vitro studies we were unable to show any direct effect of erythropoietin, used at concentrations that occurred post intravenous administration, on platelet aggregation both in whole blood and in platelet-rich plasma.

Topics: Adenosine Diphosphate; Adult; Aged; Anemia; Arachidonic Acid; Case-Control Studies; Collagen; Erythropoietin; Hemostasis; Humans; In Vitro Techniques; Middle Aged; Platelet Aggregation; Recombinant Proteins; Renal Dialysis; Ristocetin; Uremia

Topics: Adenosine Diphosphate; Arachidonic Acid; Azathioprine; Collagen; Humans; Immunosuppressive Agents; In Vitro Techniques; Kidney Failure, Chronic; Platelet Aggregation; Reference Values; Renal Dialysis; Ribonucleosides; Ristocetin; Serotonin; Uremia

Uremia causes a bleeding tendency associated with platelet dysfunction, and previous studies have shown abnormalities of platelet glycoprotein (GP) Ib or GPIIb/IIIa and a tendency for platelet activation in uremia. The present study compared the abnormalities of platelet function in uremia with (n = 1) or without (n = 18) associated Glanzmann's thrombasthenia. There was a significant difference between ristocetin-induced agglutination of platelets from the uremic patients without Glanzmann's thrombasthenia and platelets from healthy controls (n = 15). In addition, a reduction of GPIb expression by uremic platelets along with normal GPIIb/IIIa expression was confirmed using flow cytometry. Many coagulation markers were increased in the uremic patient with Glanzmann's thrombasthenia, suggesting that the coagulation was enhanced and the platelets were prone to activation. However, the thrombasthenic platelets actually showed little increase in the binding of a monoclonal anti-CD63 antibody directed against lysosomal integral membrane protein (which is expressed after platelet activation), while uremic platelets showed a marked increase. In addition, the expression of GPIb by thrombasthenic platelets was normal, while that of GPIIb/IIIa was markedly decreased. Our results suggest that thrombasthenic platelets are resistant to activation and to the degradation of GPIb under uremic condition and that this difference from 'ordinary' uremic platelets be related to the difference in GPIIb/IIIa.

Topics: Adult; Blood Coagulation; Blood Coagulation Disorders; Blood Platelets; Female; Fibrinolysis; Flow Cytometry; Fluorescent Antibody Technique; Humans; Platelet Aggregation; Platelet Membrane Glycoproteins; Renal Dialysis; Ristocetin; Thrombasthenia; Uremia

Patients with uraemia have abnormal platelet function that may be partially corrected by haemodialysis, cryoprecipitate or 1-desamino-8-D-arginine vasopressin (DDAVP). We studied the platelet von Willebrand factor receptor, glycoprotein Ib (GPIb), and plasma von Willebrand factor (vWF) in uraemic patients undergoing chronic haemodialysis. Using the slope of agglutination of formalin-fixed platelets as an index of response to ristocetin (with a constant amount of normal plasma as a source of vWF), we found the response of platelets from uraemic patients, both before (2.7 +/- 1.5, n = 40) and after dialysis (1.2 +/- 1.2, n = 40) to be significantly less than that for normal controls (14.1 +/- 10.2, n = 20; P less than 0.001). In addition, the agglutination response of platelets obtained after dialysis was less than that of platelets obtained before dialysis (P less than 0.001). Immunoblotting demonstrated decreased or absent staining of glycocalicin, a subunit of GPIb, in platelet lysates from 25 patients. All platelet samples with reduced glycocalicin also had decreased responses to ristocetin. Tritium-labelled platelets from seven patients showed decreased labelling of a protein with an electrophoretic mobility equivalent to that of GPIb (140,000 daltons). In addition, platelets with the lowest levels of surface GPIb, as demonstrated by flow cytometry, also had decreased ristocetin agglutination and decreased staining on immunoblot. Levels of von Willebrand factor antigen and ristocetin cofactor in plasma from 10 patients were generally within the normal range, although postdialysis levels tended to be higher than pre-dialysis levels. The pre- and post-dialysis plasma vWF multimeric patterns were normal.

Topics: Adult; Aged; Electrophoresis, Polyacrylamide Gel; Female; Humans; Immunoblotting; Kidney Failure, Chronic; Male; Middle Aged; Platelet Aggregation; Platelet Membrane Glycoproteins; Renal Dialysis; Ristocetin; Uremia; von Willebrand Factor

Several mechanisms have been proposed to explain the prolonged bleeding times and clinical bleeding in chronic renal failure. Recent evidence has implicated an abnormality in the structure or function of the von Willebrand factor or in its interaction with uremic platelets. We investigated this factor in 11 patients with chronic renal failure.. Blood samples for cell counts, chemistries, and coagulation studies were obtained from 11 patients with chronic renal failure and prolonged bleeding times. Concentrations of von Willebrand factor antigen and ristocetin cofactor activity were determined in plasma and platelets. Multimeric analysis of von Willebrand factor in plasma and platelets was conducted. In eight cases, the platelets of uremic patients were purified, and the thrombin- and ristocetin-induced binding of normal von Willebrand factor to these platelets was examined.. The mean plasma von Willebrand factor antigen and activity (ristocetin cofactor assay) were elevated 2.77 mu/ml and 1.88 mu/ml, respectively (normal, 1.01 mu/ml and 1.07 mu/ml, respectively). The ratio of activity to antigen in uremic plasma was 0.67 (normal, 1.05). The mean platelet von Willebrand factor antigen and activity in the uremic patients was decreased (0.26 and 0.50 mu/10(9) platelets, respectively) compared with normal patients (0.46 and 0.93 mu/10(9) platelets, respectively). The oligomeric structure of the uremic plasma von Willebrand factor lacked the largest multimers. Collection of the blood for analysis in several protease inhibitors and/or EDTA did not change the multimeric structure. The von Willebrand factor multimeric structure of platelets from uremic patients was normal. The ristocetin-induced platelet aggregation of the uremic platelet-rich plasma was decreased compared with normal plasma samples. Thrombin and ristocetin-induced binding of normal von Willebrand factor to uremic patients' platelets was indistinguishable from the binding to normal platelets.. These data suggest that the uremic platelet-binding sites for von Willebrand factor are intact and that the defect in ristocetin-induced platelet aggregation is most likely plasmatic in nature. At least one plasmatic defect was the observed reduction or absence of the largest plasma von Willebrand factor multimer in uremic patients. The platelet von Willebrand content was significantly decreased. These defects may play a role in the prolonged bleeding time and the clinical bleeding observed in patients with uremia.

Topics: Bleeding Time; Blood Platelets; Chromatography, Agarose; Humans; Kidney Failure, Chronic; Molecular Weight; Platelet Aggregation; Platelet Count; Protein Binding; Ristocetin; Uremia; von Willebrand Factor

Bleeding time, platelet retention on glass beads, and ristocetin-induced platelet agglutination (RIPA) in platelet-rich plasma were simultaneously determined for 20 patients with chronic renal failure and previous hemorrhagic history. In seven patients chosen at random out of a group of 16 in whom the three tests were abnormal, RIPA of uremic-isolated platelets in presence of normal platelet-poor plasma (PPP) and of normal platelets in presence of patient PPP were performed. In all cases, the first assay showed diminished agglutination, suggesting a platelet defect; however, uremic PPP did not inhibit the agglutination of normal platelets. In the same patients, the interaction of platelets with subendothelium was evaluated using Baumgartner's perfusion method. The subendothelial surface covered by platelets was significantly decreased in experiments with uremic whole blood when compared to normal controls. The interaction of platelets with subendothelium was also decreased when perfusions were carried out with platelet-plasma mixtures containing either normal washed platelets and uremic PPP or uremic washed platelets and normal PPP. These results show an impaired platelet adhesion caused both by a platelet and a plasmatic abnormality. Since uremic PPP decreased the adhesion of normal platelets to subendothelium but did not inhibit RIPA, it seems probable that the plasmatic defect could result in a defective binding between vWF and subendothelium. The influence of the red cell count on the platelet adhesion to subendothelium was reconfirmed by comparing perfusions of reconstituted blood with hematocrit values of 20% to 23% and 40% to 45%. In summary, a defective platelet adhesion to subendothelium has been postulated in uremic patients, caused by platelet and plasmatic alterations that are influenced by a low hematocrit.

Topics: Adult; Bleeding Time; Cell Adhesion; Endothelium; Female; Hematocrit; Humans; Male; Middle Aged; Perfusion; Platelet Adhesiveness; Platelet Aggregation; Renal Dialysis; Ristocetin; Uremia

Mean bleeding time in 11 uraemic patients improved from 11.2 (range 3.5--20) before the 5.8 (range 2.5--20) minutes during CAPD treatment (p less than 0.025). Bleeding time became normal in six out of seven patients with a prolonged bleeding time prior to CAPD. There was a concomitant improvement in platelet aggregation. Mean platelet count rose from 195 (range 117--414) to 311 (148--522) x 10(9)/L (p less than 0.01). A significant correlation was found between the change in bleeding time and in platelet aggregation induced by ristocetin, but not between the change in bleeding time and the platelet count. Our results suggest that CAPD treatment improves the uraemic bleeding tendency, even in patients on previous haemodialysis treatment.

Topics: Adenosine Diphosphate; Adult; Bleeding Time; Collagen; Epinephrine; Female; Humans; Male; Middle Aged; Peritoneal Dialysis; Peritoneal Dialysis, Continuous Ambulatory; Platelet Aggregation; Platelet Count; Platelet Function Tests; Ristocetin; Uremia

Platelet function and coagulation were tested after brief in vivo exposure to cefamandole nafate and in the presence of various concentrations of the drug in vitro. Alterations in hemostatic function were observed only with exposure to drug concentrations severalfold higher than those expected to prevail clinically.

Topics: Adenosine Diphosphate; Blood Coagulation; Blood Platelets; Cefamandole; Cephalosporins; Collagen; Epinephrine; Humans; Penicillin G; Platelet Aggregation; Ristocetin; Time Factors; Uremia