[The effect of calcium 2+ ions on the decomposition 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 Ca2+ 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- and Y-fragments were degraded further by plasmin cleavage at other positions, the greatest D-subfragment (D1) remained stable. As like as known for human fibrinogen the Ca2+ bound on a D gamma-chain position probably prevented the cleavage of a C-terminal part of the gamma-chain. By the addition of growing Ca(2+)-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-dependent transglutaminase (factor XIII). After complete proteolysis of fibrinogen (after 15 min) we observed the formation of D-dimers from canine D1-fragments. At the fibrin degradation the D-dimer 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 and -F, crosslinked through the action of transglutaminase.(ABSTRACT TRUNCATED AT 250 WORDS)