What is the complex formed by thrombin

thromboplastin is a complex composed of tissue factors and phospholipids, mainly involved in the initiation of exogenous coagulation pathways. The formation process involves the synergistic effect of coagulation factor VIIa, calcium ions, and cell membrane phospholipids, which is a key link in the coagulation cascade reaction.

1. Tissue factor:

Tissue factor is a transmembrane glycoprotein exposed after endothelial cell or tissue injury, serving as the core component of thrombin. When blood vessels are damaged, subcutaneous fibroblasts or smooth muscle cells release tissue factor, which binds to coagulation factor VII in the blood to form a complex and activate the exogenous coagulation pathway.

2. Phospholipid composition:

The platelet membrane or artificial phospholipid surface provides the phospholipid environment required for thrombin. These negatively charged phospholipids, such as phosphatidylserine, can adsorb calcium ions and coagulation factors, accelerating the conversion rate of factor X to Xa. Rabbit brain extracts are commonly used as a source of phospholipids in in in vitro assays.

3. Coagulation factor VIIa:

Activated coagulation factor VII is a functional protease of thrombin. After binding to factor VII, tissue factor is converted to VIIa through self catalysis or trace thrombin action, thereby activating downstream factors X and IX, forming a positive feedback amplification coagulation signal.

4. Calcium ion involvement:

divalent calcium ions act as cofactors to connect various protein components. Calcium ions not only maintain stable binding between coagulation factors and phospholipid membranes, but also participate in conformational changes of coagulation factor complexes. When testing in the laboratory, it is necessary to add calcium chloride solution to simulate physiological concentrations.

5. Clinical testing application:

Artificial recombinant thromboplastin is the core reagent for prothrombin time detection. By standardizing the ratio of tissue factors and phospholipids from different sources, reagents for monitoring the anticoagulant effect of warfarin can be prepared, and the international standardized ratio is established based on this principle. The stability of thrombin complex is significantly affected by temperature, pH value, and anticoagulant. Attention should be paid to the storage conditions of reagents in daily testing to avoid repeated freezing and thawing. For patients receiving anticoagulant therapy, it is recommended to regularly monitor prothrombin time and adjust the medication regimen according to the international standardized ratio. Moderate supplementation of vitamin K in a reasonable diet can help maintain coagulation factor synthesis, but it should be taken at least 4 hours apart from anticoagulant medication.