We report that a genetic polymorphism of the alpha2-adrenergic receptor (A2AR) encoded by chromosome 10 is associated with hypertension and an increase in epinephrine-mediated platelet aggregation in humans. The mechanism responsible for this heritable contrast in sensitivity to epinephrine is unknown. We tested our hypothesis that epinephrine-induced platelet aggregation is mediated by activat...

Platelet activation and aggregation by fibrillar collagens are based on substrate primary, secondary, tertiary, and quaternary structure. Although several peptides incorporating sequences from the triple-helical domains of types I and III collagen inhibit collagen-mediated platelet aggregation, none independently promote platelet activation and aggregation. It is believed that the absence of th...

A platelet aggregation inhibitory protein, bitistatin, was isolated from the venom of the puff adder Bitis arietans. This protein is a single-chain peptide containing 83 amino acids and 7 disulfide bonds. Bitistatin contains the sequence arginine-glycine-aspartic acid and shows considerable homology to two previously described snake venom platelet aggregation inhibitors, trigramin and echistati...

Pyrogallol (a generator of superoxide anions) caused 50% increase in platelet aggregation induced by 400 microM of arachidonic acid. Dipyridamole did not produce a statistically significant inhibition of arachidonic-acid induced platelet aggregation, but it caused 100% inhibition of pyrogallol-stimulated platelet aggregation. Ferrous salts (Fe2+) induced 34% platelet aggregation which was inhib...

Shear-induced platelet aggregation is important in physiological hemostasis and in the pathogenesis of arterial thrombosis. It requires extracellular Ca2+, platelet membrane glycoproteins Ib/IX and IIb/IIIa, von Willebrand factor (vWF), and ADP. We studied the effects of desmopressin (DDAVP), which increases plasma vWF levels and shortens the bleeding time, and of ticlopidine, which inhibits pl...

Coagulation and platelet function studies were performed on 24 normal subjects and 29 patients with chronic renal failure due to various causes. Thrombocytopenia was uncommon in the uraemic patients but there was reduced platelet retention in glass bead columns and platelet aggregation with adenosine diphosphate (ADP) and thrombin was slower and less complete than normal. The rate of platelet d...

The effect of a human fibrinogen preparation on in vitro platelet aggregation was assessed. Platelets were obtained from healthy volunteers. Human fibrinogen induced platelet aggregation in 65% of platelet rich plasma samples and enhanced submaximal platelet aggregation induced by heparin or by several conventional agonists in all samples. Aggregation induced by fibrinogen alone was reversed by...

Preparations of platelet concentrates (PCs) that are stored under blood bank conditions and used for transfusion purposes, appear to be enriched in platelet derived-microparticles (PMPs) with high coagulant activity that may change platelet efficacy and safety issues. High shear stress could cause shedding of PMPs from the platelet plasma membrane, platelet aggregation, and activation of the co...

The aim of this study was to explore the effects of S-nitrosoglutathione (GSNO) on the aggregation of frozen platelets, the platelet nitric oxide (NO) content and the expression of membrane glycoproteins. The level of frozen platelet aggregation was measured using a platelet aggregation analyzer, while the content of NO was measured by the nitrate reductase method and the expression of frozen p...