Biological behavior of higher molecular weight products of fibrinolysis.

We have examined the consequence of infusions into rabbits of the products of limited plasmin hydrolysis of fibrin (early fibrin degradation products, or early fdp) containing defined quantities of fibrin fragment X. For comparison, early fibrinogen degradation products (early FDP) and late fibrin degradation products (late fdp) consisting almost exclusively of core fragments D and E were infused into separate groups of animals. Components of early fdp, probably fibrin fragment X, behaved in many respects like fibrin monomer. Infused unlabeled early fdp produced circulating soluble fibrin complexes with 125I-labeled fibrinogen. 125I-labeled early fdp rapidly accumulated in the spleen and liver and also to a significant degree in the lungs as insoluble, nonextractable tissue-bound protein; in contrast, only minimal quantities of early FDP and late fdp accumulated in organs. When 125I-labeled early fdp were administered to animals given continuous infusions of epsilon-aminocaproic acid to block fibrinolysis, substantial amounts of radioisotope also accumulated in the kidneys. These observations suggest a possible pathophysiological role for the products of lysing fibrin encountered in clinical states associated with disseminated intravascular coagulation.