In Yivo Behavior of Human Fibrinogen and Fragments X, D and E.
Fragments X, D and E were obtained from plasmin digestion of purified human fibrinogen (fraction I-O). Fragment × was isolated from stage 1 digest by filtration on Sephadex G-200 by Budzinski and Marder, and fragments D and E in our laboratory by Pevikon block electrophoresis. The purified fragments were identified by immunoelectrophoresis and SDS polyacrylamide gel electrophoresis. Human fibrinogen and fragments X, D and E were labelled with 125iodine by the lactoperoxidase method. Plasma disappearance curves were studied in rabbits. A two exponential curve was obtained with all of them, with second exponential (lower slope) being clearly predominant. The half-lifes of the second exponentials were different for each fragment: there appears to be a relationship between the molecular weight of the fragments and their half-lifes. Values observed (mean±s.e.m.) were: fibrinogen 49.34±5.4 hours, fragment X 6.14±0.44 hours, fragment D 2.25±0.20 hours and fragment E 1.53±0.13 hours. No fragment was found either to polymerize or to bind to plasma proteins in vivo following injection into rabbits as demonstrated by the elution peaks obtained after filtration through Sephadex G-200.