EFFECT OF CALCIUM(2+)-IONS ON THE DEGRADATION OF CANINE AND HUMAN FIBRIN(OGEN) BY HUMAN PLASMIN

With a row of degradation kinetics with different Ca2+ concentrations and their analysis by the means of nonreducing SDS-PAGE we investigated the dependence of fibrin(ogen) degradation product patterns on the Ca(2+)concentration. At man and dog the addition of calcium stabilized from 0,06 mM Ca2+ (2.0 molecules Ca2+/molecule Fibrinogen) certain X- Y- and D-fragments which were not or not in this extent generated by degradation without calcium. The X- acid Y-fragments were degraded further by plasmin cleavage at other positions, the greatest D-subfragment (D-1) remained stable. As like as known for human fibrinogen the Ca2+ bound on a Dy-chain position probably prevented the cleavage of a C-terminal part of the gamma-chain. By the addition of growing Ca2+-concentrations (from 0.1 mM to 10 mM Ca2+) an additional, increasing D-dimer spot at a molecular weight of 220 +/- 7 kDa was formed owing to progressive activation of the concomitant calcium-dependend transglutaminase (factor XIII). After complete proteolysis of fibrinogen (after 15 min) we observed the formation of D-dimers from canine D-1-fragments. At the fibrin degradation the D-di mer was dominating already from 0,1 mM Ca2+ in the degradation assay. Especially the D-fragments, but also the smaller FDP E an -F were generated here in a reduced extent. Several new bands (= 57 kDa) were formed instead, that were probably connected FDP D, -E und -F, crosslinked through the action of transglutaminase, Summarized, the effect of Ca2+-ions on the degradation of human and canine fibrin(ogen) by human plasmin is very similar. The only dissimilarities result from differences in the molecular weights and from the dimerisation of canine D-1-fragments, which has been not described for other species up to now.