Low molecular weight fibrinogen with a modified alpha-chain is frequently found in patients with high FDP levels, but is not generated by simple in vitro proteolysis with thrombin or plasmin.
Modified fibrinogen alpha-chains associate with higher FDPs; leaves open distinct in vivo proteolytic pathways.
Plasma fibrinogen is heterogeneous with respect to molecular weight; high molecular weight fibrinogen (HMW, 340, 000) and low molecular weight fibrinogen (LMW, , 305, 000). It has been showed the LMW is formed in vivo by degradation of -COOH terminal end of α-chain of HMW.Plasma fibrinogen was obtained from 12 normal volunteeres, and analyzed by 8M Urea-SDS-PAGE migrated in the following three major position, α-(MW 67, 000), β-(MW 55, 000) and γ-chain (MW 43, 000). In 20 speciments of plasma fibrinogen from 36 patients, another component of 60, 000 in molecular weight was revealed. That was recognized as modified α-chain. The plasma fibrinogen of the other 16 patients consisted of normal three chains.The former 20 patients presented significantly higher concentration in FDP than the other 16. It could be assumed that the formation of LMW by degradation of HMW occurred in the process of blood coagulation and fibrinolysis.Therefore, we have attempted some fibrinogen amidolysis. The purified fibrinogen was catabolized by thrombin, Reptilase, Xa and plasmin. But the low molecular weight α-chain was not detected by SDS-PAGE in the process of proteolysis. Some other endothelial cell or leucocyte proteases are expected to explain this fibrinogen heterogeneity in further investigations.
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Iijima et al. (1987) studied this question.
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