The main anticoagulant action of heparin depends on antithrombin ⅲ. After combining with antithrombin ⅲ, the configuration of antithrombin ⅲ changes, and heparin can combine with a variety of coagulation factors to inhibit these coagulation factors, so as to achieve the purpose of anticoagulation. The specific mechanism is analyzed below.
The body's clotting system
The essence of blood coagulation is the process of changing soluble fibrinogen in plasma into insoluble fibrin. However, this process is very complicated, and the factors involved in coagulation include 12 factors numbered by Roman numerals, and prokinase-releasing enzyme, kinase-releasing enzyme, high molecular weight kinin progenitor, platelet phospholipid and so on. The activation process of coagulation is similar to a chain reaction, and it is currently believed that there are two pathways that can cause coagulation, namely endogenous pathway and exogenous pathway.
Endogenous pathway: Endogenous pathway means that the coagulation process completely depends on the coagulation factor in plasma and gradually activates the coagulation factor X to complete the coagulation process.
Exogenous coagulation pathway: Exogenous coagulation pathway refers to that the coagulation process is initiated by coagulation factor ⅲ released by the injured extravascular tissue and activates coagulation factor X. The following process is the same as endogenous coagulation pathway.
Those that can play the role of anticoagulation drugs, is able to inhibit a certain link in the above coagulation process, to achieve the purpose of anticoagulation. There are different anticoagulants for different sites. Heparin is an indirect inhibitor of thrombin, which inhibits thrombin. Then thrombin cannot convert soluble fibrinogen into insoluble fibrin, so as to achieve the goal of depending on you. In turn, some drugs can be made for this process to speed up the process, so it can stop the bleeding.
Specific mechanism of heparin anticoagulation
The combination of heparin and antithrombin ⅲ can change the configuration of antithrombin ⅲ, and the active site of antithrombin ⅲ will be fully exposed. After exposure, it can better combine with the coagulation factor, thus inhibiting the coagulation factor. Among them, antithrombin ⅲ can form a complex with thrombin, which leads to the reduction of thrombin's action, while heparin can speed up the reaction by a factor of 1000. When thrombin's effect is reduced, the conversion of fibrinogen to fibrin is reduced and the coagulation time is greatly prolonged. In addition, heparin also inhibits platelet aggregation, a mechanism that may also have an effect by inhibiting thrombin.