Fibrin crosslinks and lysis rates

The effect of Factor XIII-induced crosslinking of fibrin on its subsequent lysis by plasmin has been further investigated due, in part, to conflicting reports in the literature on this issue. The test system used involved I labelled plasma fibrin clots and the release of the radiolabel to measure lysis rate. It was found that, while the fibrin γ-γ crosslinks do not affect the rate of fibrin lysis, the α chain crosslinkage has a significant effect. Indeed, the increased complexity of the α chain crosslinkage endows fibrin with increased resistance to lysis. I labelled fibrin clots containing fibrin with and without crosslinked α chains, allowed the preferential removal of the non-crosslinked material. Discrepancies were noted when measuring the lysis of crosslinked fibrin only by chemical means (Lowry method) and by I labelled peptide release. Both methods of measurement are prone to criticism; however, it was found that the I release method amply reflected the release of D dimer, the major soluble structural entity in crosslinked fibrin and probably the most reliable yardstick of its lysis