The Uptake of Fibrin and Fibrin-Degradation Products by the Isolated Perfused Rat Liver

The uptake of Se⁷⁵-labeled rat fibrin and a specific preparation of fibrindegradation products by an isolated, perfused liver was studied. The rapidphase T for fibrin in the perfusate was approximately 9 minutes. This iscomparable to that found for aggregated I¹³¹ B.S.A. and colloidal gold in thesame system. The loss of activity from the blood closely paralleled the increasedactivity recorded in the liver. No radioactivity was found in the bile samplesor the T.C.A.-soluble fraction of plasma. Microradioautographs of washedliver tissue following the labeled, fibrin perfusion suggest the presence of thelabel on or in the Kupffer cells.

Labeled rat fibrin preparations, digested by the action of "cold" rat plasminto a distinct endpoint, were found to contain 3 distinct fractions on paper electrophoresis. Addition of these fractions to the perfusate resulted in approximately 25 per cent clearance of radioactivity over a 3-hour period. Hence,clearance of this specific F.D.P. preparation occurs at a much slower ratethan that of fibrin. The T as found to be in excess of 12 hours. Thesefindings appear to confirm Lee’s observation that cells of the reticuloendothelialsystem are involved in the elimination of free circulating fibrin and its metabolic products.

Submitted on February 18, 1966 Accepted on October 8, 1966