Immunoenzyme histochemical localization of fibrin degradation products in tissues

An immunoenzyme histochemical study was conducted to localize fibrin degradation products (FDPs) in rat tissues during disseminated intravascular coagulation (DIC). Serial measurements of FDP levels in serum after thrombin-induced DIC showed peak levels to be found at 30 minutes; the FDPs were rapidly cleared from the circulation (half-life about one hour). Rat tissues obtained from 10 minutes to 3 hours after the induction of DIC were studied by means of immunohistochemistry. A method was developed to differentiate FDPs from fibrin in tissue sections. This method is based on the observation that, in paraplast-embedded tissues, FDPs can be demonstrated following ethanol fixation only, and that fibrin is demonstrable after both paraformaldehyde fixation and ethanol fixation. Moreover, FDPs will react to some of the antiserums employed only, while fibrin will react to all antiserum used (antiserums against fibrin monomer, against the constituent chains of fibrinogen, and against FDP-D and -E). At 10-20 minutes after the induction of DIC, FDPs were found in kidney proximal tubule epithelial cells. These FDPs could be demonstrated using antiserum against the constituent chains of fibrinogen, but not by antiserums against FDP-D or -E. At 30-90 minutes, FDPs were found inside liver macrophages. The FDPs in liver did not react to anti-chain antiserums, though they did react to antiserums against FDP-D and -E. Since no FDPs were found in other tissues, rat FDPs are apparently cleared by kidney (earlier phase) and liver (later phase) only. In human cases of DIC, FDPs, could be demonstrated in kidney proximal tubules cells and in liver macrophages as well.