Soluble high-molecular-weight E fragments in the plasmin-induced degradation products of cross-linked human fibrin

Compaction as a method to characterise fibrin network structure: kinetic studies and relationship to crosslinking

While it has been shown that compaction is inversely correlated to the Young's modulus of elasticity of the network and to the final strength at break, the relationship between collapsibility of the network subjected to a standardised centrifugal force and the degree of crosslinking (i.e., compaction) has not been properly addressed. Three sets of networks developed from plasma and pure fibrinogen solution, with varying degree of crosslinking induced by the addition of different amounts of calcium, were subjected to centrifugation at 8000g. In networks developed from plasma, compaction correlated with the degree of crosslinking. Whilst totally crosslinked clots were most resistant to collapse, partially crosslinked clots were far less resistant to collapse. In purified fibrinogen, however, the effect crosslinking was all or nothing. Both totally crosslinked and partially crosslinked clots were equally resistant to collapse. Calcium induced crosslinking provides fibrin with the required strengthening of the fibrin network. However, there are also fibre to fibre interactions as can be observed in networks developed in the presence of drugs like gliclazide. Compaction is a simple technique which can be used in any clinical laboratory to characterise the degree of crosslinking and also the tensile properties of the network.

Roles for chloride ion and fibrinogen in the activation of [Glu1]plasminogen in human plasma

Using two-dimensional immunoelectrophoresis and an antibody to alpha 2-antiplasmin, we assessed the plasmin generated in serum under different conditions as the plasmin-alpha 2-antiplasmin complex. Activation in serum of human [Glu1]plasminogen ([Glu1]Pg) by recombinant tissue plasminogen activator was inhibited by the normal serum levels of Cl- and was enhanced by physiological levels of fibrinogen in the presence or absence of Cl-. These results agree with the recognized ability of Cl- to induce a conformation in [Glu1]Pg less favorable for its activation than the conformation that results without Cl-. The enhancing effect of fibrinogen surpassed the inhibitory effect of Cl- over a wide range of recombinant tissue plasminogen activator concentrations in physiological serum. Lesser inhibition by Cl- was seen in a purified clot-lysis system, suggesting that [Glu1]Pg conformation when attached to soluble fibrin matrix was less affected by the anion. The data regarding the roles of circulating fibrinogen and Cl- in controlling the plasma level of activated [Glu1]Pg have important implications in thrombolytic therapy with recombinant tissue plasminogen activator.