Summary
Human or canine fibrin polymers which are structurally altered by the combined action
of plasmin and EACA show an increased resistance to digestion by trypsin, but not
to digestion by chymotrypsin. These observations support the concept that EACA inhibition
of fibrinolysis is to a variable extent a function of structural changes in the substrate,
and that the changes may be related to the susceptibility of lysyl- and arginyl-sites
attacked by plasmin and trypsin, but not by chymotrypsin.
In plasma, the fibrin modification reactions mediated by plasmin + EACA are analogous
to those in purified systems, with quantitative differences resulting from the presence
of other inhibitors, and perhaps from earlier gelation of the developing polymers.
This complexity of the action of EACA must be taken into account in comparing its
effects with those of other inhibitors, which also have variable and non-linear effects
related to prevention of autodigestion of plasmin, antagonistic or potentiative combinations
of inhibitors, and interference with substrate conversion.
