platelet activation

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The process whereby platelets adhere to collagen released from endothelial cells in damaged blood vessels and aggregate to form a plug. An important metabolic pathway in platelets converts membrane phospholipids to thromboxane A2 (TXA2), which can activate platelets. ADP, released from platelet granules, and thrombin are other activators. The adhesive and aggregation reactions of platelets are mediated through surface membrane glycoproteins (Glp), Glp Ib and Glp IIb/IIIa. Aspirin acts as an antiplatelet drug by irreversibly inhibiting one of the enzymes of this pathway, cyclo-oxygenase. Clopidrogel inhibits the ADP receptor on platelet membranes, and abciximab blocks platelet aggregation by inhibiting Glp IIb/IIIa (see illustration).

Platelet activation. The stages of the process and sites of action of antiplatelet drugs.

Subjects: Medicine and Health.

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