Effect of platelet activation on the agglutination of platelets by von Willebrand factor

• Published in: Molecular pharmacology Vol. 37; no. 2; pp. 271 - 277
• Main Authors: MILLS, D. C. B, HUNCHAK, K, KARL, D. W, KIRBY, E. P
• Format: Journal Article
• Language: English
• Published: Bethesda, MD American Society for Pharmacology and Experimental Therapeutics 01.02.1990
• Subjects: Adenosine Diphosphate - pharmacology; Agglutination - drug effects; Biological and medical sciences; Blood coagulation. Blood cells; Blood Platelets - cytology; Blood Platelets - drug effects; Cyclic AMP - blood; Drug Interactions; Fundamental and applied biological sciences. Psychology; Humans; In Vitro Techniques; Molecular and cellular biology; Platelet; Platelet Activation - drug effects; Platelet Aggregation - drug effects; Ristocetin - pharmacology; von Willebrand factor; von Willebrand Factor - physiology; Epinephrine; Human; Agonist; Radiolabelling; Aminoacid derivative hormone; Glycoproteins; Catecholamine; ADP; Adenylate cyclase; Platelet; Enzymatic activity; Agglutination; Inhibition; Willebrand factor; Coagulation factor
• ISSN: 0026-895X; 1521-0111

Agglutination of human platelets by bovine von Willebrand factor (vWF) or by human vWF in the presence of ristocetin is inhibited by ADP and by several other platelet agonists but not by epinephrine. Vincristine, which causes a shape change by disrupting microtubules, neither inhibited agglutination nor blocked the effect of ADP. The action of ADP was blocked by ATP, by p-fluorosulfonylbenzoyladenosine, and by the thiol-reactive regents cytochalasin A and p-chloromercuribenzenesulfonate. In contrast to its effects on vWF, ADP enhanced agglutination induced by wheat germ lectin. ADP caused a small decrease in the number and affinity of binding sites for vWF on platelets, too small to explain the inhibition of agglutination. The ability of ADP and other agonists to inhibit agglutination appears to be related neither to inhibition of adenylate cyclase nor to the loss of their discoid shape but rather to the membrane changes that accompany the shape change.