To quantitate plasmic degradation products of crosslinked fibrin in plasma, a technique has been developed which employs heat precipitation, SDS-polyacrylamide gradient gel electrophoresis of the dissolved, reduced heat precipitate, and quantitation by densitometrie analysis of γ-γ derivatives identified in the stained get. When studied with this sensitive electrophoretic technique, plasmic digests of purified crosslinked fibrin were found to contain a heterogeneous group of γ-γ chain derivatives with molecular weights between 76,000 and 100,000 daltons. In samples of normal plasma to which digests of crosslinked fibrin had been added, this heat extraction/ge1 electrophoretic technigue allowed the detection of γ-γ derivatives with a sensitivity of 20 µg/ml. Derivatives of γ-γ chains with molecular weights of 82,000 and 86,000 daltons have been identified in the plasma of patients with DIC and during fibrinolytic therapy but were not found in normal plasma or in normal plasma treated in vitro with urokinase. This quantitative assay can be performed in 24 hours and appears to be of value in judging the efficacy of thrombolytic therapy.
