The lysis of intravascular thrombi in rabbits with human plasmin (fibrinolysin).

Streptokinase produces it-s lytic effect by activation of a profibrinolysin usually called plasminogen. Many attempt-s have been made to isolate this latter material for investigation without consistent success.#{176}’ ‘#{176} A new method for preparation of this material (plasminogen)’t ‘ 12 has recently been reported. In vivo stu lies of activated plasminogen (plasmin) in dogs and rabhit-&3 have indicated that itis nontoxic and that it effects a marked increase in the lytic activity of the plasma. The present study was undertaken to establish the effectof this material (1111man plasmin) on intravascular clots. Thromboses in the marginal veins of the rabbitear have been a favorite medium for testing the effect of lyt-ic agents. The experience of others, with this method, has served as a basis for further study. To study the effect of plasmin on thrombi in vivo, itwas firstnecessam’y to produce them in a standard fashion. Jacques’4 has pointed out the difficulty of producing thrombosis in normal animals. It has been show’n that isolation between ligatures of a stationary column of blood in a vein would produce small nonadherent thrombi.’5 Thrombosis has been pi’oduced by the injectiomi of thromboplastin iiito veiii segments in dogs,’6 by sevei’e trauma,’7’ 18 by infection,’11 and by chemical irritants.2022 O’Neill23 show-ed that partial obstruction and interference w’ith the nutrition of the vein in dogs produced clots only after twenty to fifty hours. In our experiments sodium morrhuate ‘as found to give 10() pet’ cent reproducible production of thrombi. Many studies have been made of the effect of know’n drugs in causing lysis of preformed clots in experimental animals. Heparin has been show-n to have some thrombolyt-ic effectin early thrombi)#{176}’ 24 Tromexan, administered over a long period of time, has been found to promote recanalization of thrombi in rabbits’ ear veins,2’ in the femoral vein of dogs,22 aiid in the femom’al artery of rabbits.2#{176} Trypsin, administered over a long period of time, has been show’n to lyse thrombi