Fibrinogen Quick Facts
Molecular mass: HMW: 340 000 D; LMW: 305 000 D; LMW : 270 000 D
- 1.7 – 4g/l Clottable fibrinogen
- 2.5 – 6g/l Fibrinogen concentration
Half-life: 3 days
Biochemistry of Fibrinogen
The dimeric glycoprotein fibrinogen (factor I) consists of 2 Aα-, 2 Bβ- und 2 γ-chains. After cleavage of the fibrinopeptides A and B, the resulting fibrin monomers polymerize to form soluble fibrin. This soluble form is subsequently crosslinked to insoluble fibrin by factor XIIIa. Fibrinogen and fibrin can be cleaved by the fibrinolytic enzyme plasmin, resulting in fibrin (ogen) degradation products FDP. Fibrinogen can also be broken down by other proteases, e.g. PMN-elastase.
Fibrinogen has various functions in plasma:
- Platelets are bound to fibrinogen and fibrin via the receptor GPIIb/IIIa.
- The fibrinogen concentration regulates the plasma viscosity.
- In cases of inflammation the fibrinogen concentration increases, as it is one of the acute phase proteins.
- Fibrin plays a major role in fibrinolysis, as fibrinolytic factors such as plasmin inhibitor, plasminogen and t-PA adhere to its surface and react with their targets.
Clinical significance of Fibrinogen
Low fibrinogen concentrations are seldom observed. When found, it is mainly in acute situations such as DIC, hyper-fibrinolysis, liver damage and systemic fibrinolytic therapies. Acquired dysfibrinogenemias are more often seen than congenital dysfibrinogenemias, especially in liver disease. Increased fibrinogen concentrations are often observed. In acute inflammatory diseases, fibrinogen concentrations > 10 g/l have been observed. Fibrinogen is regarded as a risk factor for coronary and cerebral vascular disease, if the plasma level remains above 3 g/l over a longer period of time.
Clinical or Research use of Fibrinogen
- Monitoring of DIC
- Monitoring of hyperfibrinolytic therapy
- Monitoring of fibrinogen substitution therapy
- Suspected hereditary fibrinogen deficiency and/or dysfibrinogenemia
- Increased fibrinogen concentrations in various diseases
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