Hemostatic process

Hematophagous species secrete a plethora of proteinaceous molecules that interfere with discrete biochemical events and adversely affect the host s hemostatic process [49]. These include hirudin [50] and antistasin [51] which inhibit thrombin and factor Xa, respectively. Proteins exhibiting fibrinolytic and antiplatelet activity have also been isolated [52-54]. 

It is well known that platelets play an important role in the hemostatic process, and their aggregation can lead to arterial thrombosis [94]. Therefore, evaluation of compounds with antiplatelet aggregation activity... 

Hemostasis is the process of blood clot formation at the site of vessel injury. When a blood vessel wall breaks, the hemostatic response must be rapid, localized, and carefully regulated. Abnormal bleeding or a propensity to nonphysiologic thrombosis (i.e., thrombosis not required for hemostatic regulation) may occur when specific elements of these processes are missing or dysfunctional. The elements responsible for normal hemostasis have received extensive review. 

The first reason is theoretical. The demonstrated effects of the new substances and combinations on lipids and carbohydrates do not have any major relevance to the thromboembolic process. The latter is linked primarily to changes in the hemostatic system and blood coagulation, involving platelet aggregation, coagulation factors, fibrinogen concentrations, and blood viscosity. 

This hemostatic/prothrombotic process is counterbalanced by vascular prostacyclin (PGl2) derived predominantly from COX-2 activity and nitric oxide (NO) released from endothelial cells. In vascular endothelial cells, COX-2 produces primarily PGI2 that inhibits platelet aggregation, induces vasodilation, inhibits the proliferation of vascular smooth-muscle cells, and is less susceptible to inhibition by low doses of aspirin. PGI2 and NO induce an intracellular increase of second messengers. NO inhibits platelet function by stimulation of a soluble guanylyl cyclase to produce cGMR... 

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