title: The release of small amounts of fibrinopeptide-B (FPB) is of critical importance for the thrombin clotting time.
abstract: When fibrinogen is clotted with thrombin, mainly fibrinopeptide-A (FPA) is released at gel point, the FPB-release being delayed. The present study present evidence that the small amounts of des-AABB fibrin found at visible gelation improves polymerization, thereby determining the thrombin clotting time. 1. Purified fibrinogen was clotted with thrombin or Reptilase, peptide release monitored radioimmunologically. With thrombin, significantly less fibrin (released FPA) was necessary for gel formation than when Reptilase was used. Furthermore, approximately 10% of the available FPB had been released by thrombin at gel point. 2. Polymerization of monomers prepared by incubation of fibrinogen with Reptilase (des-AA) and thrombin (des-AABB) in urea, were examined by light scattering. Des-AA fibrin monomers polymerised after a lag-phase of 4 minutes. When 20% of these monomers were substituted with des-AABB monomers, the lag was reduced to 1 1/2 minutes. 3. Finally, polymerization of preformed des-AA monomers was studied with and without the addition of small amounts of thrombin, and the FPB-release monitored. The presence of 0.04 NIH U/ml of thrombin reduced the lag from 10 minutes to 3 minutes. At this time approximately 10% of FPB had been released. It is concluded that even small amounts of des-AABB fibrin substantially improves polymerization of des-AA fibrin.
mesh_terms: D001780:Blood Coagulation Tests; D005338:Fibrin Fibrinogen Degradation Products / Q000378:metabolism / Q000502:physiology; D005340:Fibrinogen / Q000502:physiology*; D005344:Fibrinopeptide A / Q000378:metabolism / Q000502:physiology; D005345:Fibrinopeptide B / Q000378:metabolism / Q000494:pharmacology / Q000502:physiology*; D011108:Polymers; D013918:Thrombin Time; D013997:Time Factors
chemical_list: D005338:Fibrin Fibrinogen Degradation Products; D011108:Polymers; C011468:fibrinmonomer; D005344:Fibrinopeptide A; D005345:Fibrinopeptide B; D005340:Fibrinogen