Fibrinolysins from Fibrin Clots

Abstract

THREE fibrinolytic agents have been encountered in fibrin clots. The first was described as lytic factor in an earlier communication¹. It was extracted with borate from trypsin-digested clots. It has since been found that extraction can be carried out successfully with 0.9 per cent sodium chloride and other salt solutions. Active preparations contained a 17-ketogenic steroid and were inactivated by β-glucuronidase and by heating at 56° C for 30 min. The inhibitory effect of potent lytic factor on the clotting of fibrinogen by thrombin or aqueous clot extract¹ was very marked. An amount of 0.0004 ml. prevented fibrin formation, while with 0.0002 ml. only a partial clot was produced. With recalcified oxalated plasma different reactions were observed. One-hundredth ml. of the same preparation induced formation of a complete clot in 30–35 sec; with 0.05–0.08 ml. partial clots formed in the same time interval, while 0-15 ml. prevented clotting entirely. The lytic activity of the factor was strongly inhibited by serum, even after the serum had been treated with 0.2 N sodium hydroxide to destroy glucuronides and then neutralized with hydrochloric acid.