Crosslinking of Fibrinogen and Fibrin by Fibrin Stabilizing Factor

Fibrin stabilizing factor (FSF) catalyzed intermolecular crosslinking of fibrinogen. Differing from the known zero-order relationship in fibrin crosslinking, the rate of crosslinking of fibrinogen depended on its concentration (first-order). When the concentraction was extremely high, FSF rapidly catalyzed crosslinking to produce gelation of fibrinogen. This observation suggests that filtrational condensation of fibrinogen may contribute to deposition of insoluble fibrinogen in atheromatous tissue.In studies on mixtures of fibrinogen and fibrin, FSF showed almost equal affinities to both substrates; and, a) at low concentration of fibrinogen, in which crosslinking of fibrinogen proceeded very slowly compared to fibrin, fibrinogen inhibited the stabilization of fibrin clots by competitively binding to FSF.b) at high concentration of fibrinogen, in which fibrinogen could solubilize small amount of fibrin by forming the soluble fibrinogen-fibrin complex and inhibit fibrin clot formation, stabilization of soluble fibrinogen-fibrin complex by FSF added further inhibition of stabilization of fibrin clots. These findings may suggest the mechanism in which fibrinogen inhibit both polymerization and crosslinking of fibrin being produced in the circulating blood.