High Fibrinogen (Fg) Content in Plasma Clots Harvested At Arrested, Incipient Coagulation

Incomplete transformation of Fg to fibrin may occur in vivo and in vitro,especially in connection with the use of heparin. We have studied to what extent unproteolyzed Fg is incorporated in plasma clots harvested at early and late arrest in Fg to fibrin conversion. Since des-AA fibrin will predominate in clots harvested at incipient gelation whilst des- AABB fibrin will be characteristic of clots harvested at late stages in Fg to fibrin conversion, preformed, enzyme-free des-AA or des-AABB fibrin monomers were added in varying amounts to Fg-boosted, inactivated serum containing varying Fg concentrations. (Fg + fibrin= 2 g/1 in all samples) . Labelled monomers or labelled Fg were used. The clots were harvested, squeezed, washed and Fg/fibrin ratio of clots calculated on the basis of recorded radioactivity. All clots contained Fg,but substantially more when formed at high Fg/fibrin rations (incipient gelation) than at low (late stages in Fg to fibrin conversion). Thus, clots formed at Fg/fibrin ratio=9/l contained 3 times as much Fg as fibrin, whilst clots formed at a Fg/fibrin ratio=l/9 contained Fg/fibrin=l/20.Presence of preactivated FSF(activated by insolubilized thrombin) did not influence the Fg/fibrin ratio of clots. Streptokinase-induced intraclot lysis rate of clots containing Fg were substantially higher than of clots containing fibrin only, a finding especially noticeable in clots with a high Fg content, and might explain the low thromboembolic complication rate seen in arvin/reptilase therapy. Finally, it should be stressed that clots harvested at incipient gelation contain large amounts of Fg, which may lead to misinterpretation as to the amount of fibrin actually formed.