Article

Platelets: Physiology and biochemistry

Department of Anaesthesiology and Intensive Care, Experimental and Clinical Haemostasis, University-Hospital Münster, Münster, Germany.
Seminars in Thrombosis and Hemostasis (Impact Factor: 3.69). 02/2005; 31(4):381-92. DOI: 10.1055/s-2005-916671
Source: PubMed

ABSTRACT Platelets are specialized blood cells that play central roles in physiologic and pathologic processes of hemostasis, inflammation, tumor metastasis, wound healing, and host defense. Activation of platelets is crucial for platelet function that includes a complex interplay of adhesion and signaling molecules. This article gives an overview of the activation processes involved in primary and secondary hemostasis, for example, platelet adhesion, platelet secretion, platelet aggregation, microvesicle formation, and clot retraction/stabilization. In addition, activated platelets are predominantly involved in cross talk to other blood and vascular cells. Stimulated "sticky" platelets enable recruitment of leukocytes at sites of vascular injury under high shear conditions. Platelet-derived microparticles as well as soluble adhesion molecules, sP-selectin and sCD40L, shed from the surface of activated platelets, are capable of activating, in turn, leukocytes and endothelial cells. This article focuses further on the new view of receptor-mediated thrombin generation of human platelets, necessary for the formation of a stable platelet-fibrin clot during secondary hemostasis. Finally, special emphasis is placed on important stimulatory and inhibitory signaling pathways that modulate platelet function.

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    • "The addition of 10% collagen to the xenogenic BSM enhanced platelet degranulation in a obvious manner. Platelet consumption also stands for degranulation and cytokine release (Jurk & Kehrel 2005). In accordance, cytokine concentrations analog to the respective platelet activation were expected. "
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    • "The platelet lifespan is approximately 7 to 9 days, which they spend circulating in the blood in their resting form. When adhered to exposed endothelium or activated by agonists, they change their shape and secrete the contents of the granules (including ADP, fibrinogen, and serotonin), which is followed by platelet aggregation [7]. Initiation of the signaling event within the platelet leads to the reorganization of the platelet cytoskeleton, which is visible as an extremely rapid shape change [17] "
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    • "At sites of blood vessel injury, platelets are activated to induce blood coagulation and form aggregates at the site of the damaged endothelium to prevent hemorrhage and thereby protects us from fatal bleedings. Besides their role in hemostasis, platelets have been shown to contribute to nonhemostatic processes such as wound healing, immunity, angiogenesis, cardiovascular disease and tumor metastasis (Felding-Habermann et al., 1996; Jurk and Kehrel, 2005). A connection between platelets and malignant disease has been recognized since the end of the 19th century, when Armand Trousseau observed increased thrombotic events in patients that were later diagnosed with cancer (Trousseau, 1865). "
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