Fibrinolysis is triggered when injured endothelial cells release tissue plasminogen activator (tPA), which then cleaves plasminogen (which is bound to fibrin) to plasmin. Fibrin markedly enhances the activity of plasmin. Plasmin lyses fibrin into degradation products, including non-crosslinked fibrin degradation products and cross linked products, the smallest of which is D-dimer. A complex of the contact pathway factors of activated Factor XII (FXIIa) and kallikrein converts high molecular weight kininogen into bradykinin, which is a potent stimulus of tPA release. Both FXIIa and kallikrein can also activate plasminogen to plasmin but are far weaker than tPA.
“Reproduced and modified with permission from the BSAVA Manual of Canine and Feline Clinical Pathology, 3rd edition.”
