SIGNIFICANCE OF CRYOPROFIBRIN IN FIBRINOGEN-FIBRIN CONVERSION

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Abstract
Fibrinogen altered by thrombin-catalyzed liberation of fibrinopeptide A was found to combine with native fibrinogen to form a cold-precipitable complex we have called "cryoprofibrin." The altered fibrinogen lacking fibrino-peptide A polymerized into fibrin, but not until conditions for equilibrium between its incorporation into both cryoprofibrin and fibrin were satisfied. At equilibrium, the concentration of cryoprofibrin was maintained at a threshold proportional to the concentration of fibrinogen. When the concentration of cryoprofibrin was below threshold, fibrin could be depolymerized and solubilized by fibrinogen with resultant formation of cryoprofibrin. Since threshold concentrations of cryoprofibrin appear necessary for precipitation of fibrin, the concentration of cryoprofibrin in plasma provides a basis for determining intravascular deposition of fibrin. Intravascular deposition of fibrin does not appear to occur normally in rabbits, because the concentration of cryoprofibrin in plasma from normal rabbits is far below the threshold for precipitation of fibrin. The applicability of cryoprofibrin as an indicator of fibrin deposition is demonstrated by the occurrence of levels of cryoprofibrin approaching the threshold for precipitation of fibrin in plasma from endotoxin-treated rabbits.