Plasma Fibrinogen and Factor XIII During Intermittent Thrombolytic Therapy

The precursor components of the fibrin crosslinking system, viz, fibrinogen, and Factor XIII have beer, studied in plasma from patients undergoing intermittent thrombolytic therapy. Fibrinogen was isolated as fibrin monomer in the presence of EDTA and Trasylol and the level of degradation of the subunits quantitated by densitometric scans after separation on SDS gels Plasma samples were also clotted in the presence of calcium and the crosslinked subunits separated on SDS gels. Gels were radioiodinatedusing a chloramine T method, then sliced and counted to determine the amounts of γ dimer and α polymers. Daily single infusion of streptokinase caused degradation of circulatory clottable fibrinogen such that about 80% contained degraded chains MW 25,000. In crosslinked fibrin prepared from the plasma there was no diminution of the relative amount of γ dimer formed but tha of the high molecular weight α polymers was greatly reduced. In the interval between infusion of streptokinse (12 hours) the fraction of undegraded fibrinogen returned to near normal which was associated with an increased capacity to form α polymers, Three methods were used to determine Factor XIII Levels during therapy, viz, dansyl cadaverine incorporation, immunoelectrophoresis (a and b subunits) and the rate of formation of γ dimers and α polymers using ¹²⁵I fibrinogen free of Factor XIII. Over the course of the therapy Levels fell by 30% of the pretreatment value using the first two methods, slightly great er losses being observed using the third procedure. The daily fluctuation of plasma levels observed with fibrinogen, pre and post streptokinase infusion did not occur with Factor XIII.