Which of the following is the binding site for the von Willebrand factor multimers on the platelets?
Correct Answer: Glycoprotein 1b
Description: Von Willebrand factor binds on platelets to the specific receptor glycoprotein 1b when acting as a bridge between the platelets and the site of vascular injury. ADP is released by damaged erythrocytes and helps VWF to adhere to the exposed collagen. It is not, however, the binding factor that connects the VWF to the platelets. Factor VIII does not paicipate directly in the platelet poion of blood clot formation. Thromboxane A2 promotes subendothelial exposure after vascular injury and induces platelet aggregation. Also Know: Von Willebrand Disease is the most common inherited bleeding disorder. VWF serves two roles: (1) as the major adhesion molecule that tethers the platelet to the exposed subendothelium; and (2) as the binding protein for FVIII, resulting in significant prolongation of the FVIII half-life in circulation. The most common type of VWD is type 1 disease, with a parallel decrease in VWF protein, VWF function, and FVIII levels, accounting for at least 80% of cases. Patients have predominantly mucosal bleeding symptoms, although postoperative bleeding can also be seen. Menorrhagia is a common manifestation of VWD. The mainstay of treatment for type 1 VWD is 1-deamino-8-d-arginine vasopressin (DDAVP, or desmopressin), which results in release of VWF and FVIII from endothelial stores. Ref: Konkle B. (2012). Chapter 115. Disorders of Platelets and Vessel Wall. In D.L. Longo, A.S. Fauci, D.L. Kasper, S.L. Hauser, J.L. Jameson, J. Loscalzo (Eds), Harrison's Principles of Internal Medicine, 18e.
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