Effects of Thrombin Infusions upon ¹³¹I‐labelled Fibrinogen in Dogs

Abstract

Abstract N ordström , S. and E. Z etterqvist . Effects of thombin infusions upon 131 I‐labellad fibrinogen in dogs . Acta physiol. scand. 1968. 72 . 85–99. The elimination of 131 I‐labelled fibrinogen was followed in 5 groups of dogs: 1. after thrombin infusion, 2. after thrombin infusion in heparinized dogs, 3. after simultaneous infusions of epsilon aminocaproic acid (EACA) and thrombin, 4. after simultaneous infusions of Trasylol and thrombin and 5. controls. Platelet number, fibrinogen concentration and radioactivity in plasma and fibrinogen were determined. Thrombin caused an immediate fall of both plasma and fibrinogen radioactivity. The plasma radioactivity, however, soon started to increase. This secondary increze of plasma radioactivity seemed to be due to fibrinogen‐fibrin degradation products. This indicates that the thrombin‐induced intravascular coagulation gives rise to a secondary fibrinolytic process. In heparinized dogs the coagulation‐promoting effect of thrombin was inhibited. EACA and Trasylol in large doses, given simultaneously with thrombin, had no effect on the coagulation process but prevented the secondary plasma radioactivity increase. The fibrinogen‐fibrin degradation products at different times were calculated. It was also possible to estimate the amount of synthetized fibrinogen at the different times. The highest mortality was obtained in the Trasylol‐thrombin group. A probable explanation is that Trasylol is more effective than EACA in preventing the compensatory clot‐dissolving fibrinolysis.