Abstract
The process of the fibrinogen-fibrin conversion under a velocity gradient was observed by using a flow birefringence apparatus. This was done in order to investigate the role of the release of fibrinopeptides A and B (FPA and FPB) in the formation of the fibrin structure. Fibrinogen, whose FPA and/or FPB are released by thrombin or reptilase, forms fine clots at high pH and/or high ionic strength, while the hydrolyzed fibrinogen forms coarse clots at lower pH and/or low ionic strength. Under experimental conditions, when forming fine clots, a clear chromatic polarization was observed by the flow birefringence measurement only in the fibrinogen and thrombin systems at a given velocity gradient, e. g., 1, 670s-1. On the other hand, no flow birefringence was observed in the fibrinogen and reptilase systems under experimental conditions when forming fine or coarse clots. The occurrence of flow birefringence in the fibrinogen-thrombin systems indicates the formation of optically anisotropic particles at a given range of velocity gradient. Thus, the anisotropic particles, formed from fibrin monomer catalyzed by thrombin, could be distinguished from isotropic particles formed by reptilase, by using the flow birefringence observation. The release of FPB appears to be a major contributing factor in disturbing the formation of isotropic particles, caused by aggregation of fibrin protofibrils.
