Hemostasis, platelet role

Each component of blood has a function ia the body. Red cells transport oxygen and carbon dioxide between the lungs and cells ia the tissues. White cells function as defense of the body. Platelets are important for hemostasis, ie, the maintenance of vascular iategrity. Plasma, an aqueous solution containing various proteias and fatty acids, transports cells, food, and hormones throughout the body. Some proteias ia plasma play a role ia clotting, others are messengers between cells. 

Platelets play an important role in hemostasis and are involved in the pathogenesis of many diseases, such as artherosclerosis and asthma. Moreover, an inadequately controlled aggregation may lead to vascular occlusion. 

Platelets play a central role in primary hemostasis. They are also important in pathological processes leading to thrombosis. Antiplatelet drugs are primarily directed against platelets and inhibit platelet activation by a number of different mechanisms. They are used for the prevention and treatment of thrombotic processes, especially in the arterial vascular system. 

We shall first describe the coagulation pathway leading to the formation of fibrin. Then we shall briefly describe some aspects of the involvement of platelets and blood vessel walls in the overall process. This separation of clotting factors and platelets is artificial, since both play intimate and often mutually interdependent roles in hemostasis and thrombosis, but it facifitates description of the overall processes involved. 

Describe the processes of hemostasis and thrombosis, including the role of the vascular endothelium, platelets, coagulation cascade, and thrombolytic proteins. 

Discuss the role of platelets in various aspects of hemostasis... 

Platelets play a role in each of the mechanisms of normal hemostasis vasoconstriction, formation of the platelet plug, and blood coagulation. However, they are also involved in pathological processes that lead to atherosclerosis and thrombosis (formation of a blood clot within the vascular system). Antiplatelet drugs interfere with platelet function and are used to prevent the development of atherosclerosis and formation of arterial thrombi. 

Blood platelets release ATP, ADP, serotonin, and other compounds and this plays an important role in thrombosis and hemostasy. To study the mechanism of the release, in vitro release of ATP was followed using the firefly luciferase luminescence method [124],... 

Packham MA, Role of platelets in thrombosis and hemostasis, CanJ Physiol Pharmacol 1994 72 278-284. 

Platelet activation by ADP and adenosine triphosphate (ATP) is a key player in hemostasis and thrombosis, Several receptors are involved, and there are a number of drugs that target these receptors (I). The P2XI receptor is an ATP-gated channel but its role is not yet well defined. 

PDI is a noncovalent homodimer with a molecular weight of 57 kDa for each subunit. The protein is generally involved in the formation, reduction and rearrangement of disulfide bridges and plays an important role in platelet function. PDI is localized at the extracellular side of the plasma membrane and is secreted after platelet activation (Chen etal, 1992). In platelets, PDI catalyzes the formation of disulfide-bridged complexes of thrombospondin 1 and thrombin-antithrombin III and is thus involved in hemostasis and wound healing (Milev and Essex, 1999). 

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