Platelet Activation and Responses

Proteins released from the platelet granules may also bind to the platelet surface. Components of the a-granules such as thrombo oncfo (Aiken et al, 1987), platelet ctor 4 (Capitanio et al, 1985), fibrinogen, fibronectin and PDGF bind to their respective receptors on the platelet surhice. This concerns also ADP and serotonin from the dense graimles (discussed further in 9.7). Pho hatidylserine (PS) which is normally located on the iimer bilayer of the platelet membrane, broomes exposed on the outer surface of die membrane in activated platelets (Bevers et al, 1983). 

Activated platelets provides a surface for assembly of the enzyme complexes that lead to the generation of thrombin. The prothrombinase reaction results in the enzymatic conversion of prothrombin to thrombin. Prothrombinase is a complex composed of activated factor V, activated Factor X, Ca and prothrombin (Tracy and Mann, 1986 Kane and Davie, 1988). As described in 9.3.6, these sites for assembly are also present on MPs. 

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Sl N VM, HtXMSEN H. Current aspects on human platelet activation and responses. EurJHaematol 38 383-399,1987. 

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