Effect of increased fibrinogen concentration on the lysis of in vivo thrombi.

THE significance of the fibrinogen content of the blood in the clotting mechanism has received little consideration except for the effects of obvious hypofibrinogenemia in hemorrhagic states. Hyperfibrinogenemia occurs in many conditions that are associated with thrombotic complications and may be a factor in their formation. The purpose of the present study has been to compare the response of thrombi formed at normal and at increased blood fibrinogen levels to treatment with fibrinolysin. The rate and completeness of any enzymatic reaction will be a function of both the amount of substrate and the amount of enzyme available. This relationship has been demonstrated repeatedly' for the fibrinolytic enzyme system. Guest, Ware, and Seegers found that the lysis time of a purified bovine fibrin clot would increase in direct proportion to the amount of fibrin in the clot in the presence of a given amount of chloroform activated bovine plasniin.'In vitro studies, using bovine fibrin clots and a fibrinolytic system composed of streptokinase activated plasminogen, have been reported. The rate of fibrin breakdown was determined by the amount of nitrogen released from the clot. Release of radioactivity from labeled fibrinogen clots was also measured and similar results were obtained. Fibrin breakdown was found to be slow and incomplete when the clot was formed at fibrinogen concentrations of more than 450 ing. per cent. A