EFFECTS OF INTRAVENOUS INJECTIONS OF THE ANTICOAGULANT FRACTION OF INCUBATED FIBRINOGEN ON BLOOD COAGULATION

Abstract

AFIF (Anticoagulant Fraction of Incubated Fibrinogen precipitated between 25 and 50% ammonium sulphate saturation) prepared from Armour''s incubated bovine fibrinogen was injected in a dosage of 46-106 mg (mean: 66.5 mg) tyrosine per kilogram body weight in the external jugular vein of 10 rabbits. Blood samples were withdrawn at 1/2- or 1-hour intervals until the aspirated blood began showing signs of coagulation. The anticoagulant effect was manifested immediately and lasted for 2 1/2 to 5 1/2 hours in the animal. Although the blood aspirated during this time remained unclotted even after 24 hours, the surgical wound in the neck of the animal did not bleed and autopsies revealed no sign of internal haemorrhage. The bleeding time, however, was found prolonged when tested by cutting the marginal vein of the ear. The level of the coagulation factors was determined both in oxalated specimens and in specimens with no anticoagulant added. Both kinds of sample showed: (1) clottable fibrinogen content normal, thus excluding fibrinolysis as the cause of the anticoagulant effect; (2) thrombin clotting time of infinity; (3) one-stage prothrombin time longer than 60 seconds; (4) no correction of the infinite thrombin clotting time of oxalated specimens following the addition of 0.25 mg protamine per ml. This makes unlikely any appreciable release of heparin by the. animal. However, oxalated and non-oxalated specimens differed in the following respects: (1) prothrombin time determined after adsorption and mixing of the eluate with adsorbed plasma was found to be normal for the oxalated blood but variably increased for the non-oxalated specimen (10-34.5 seconds); (2) the plasma precursors of plasma thromboplastin were normal in oxalated but very low in native specimens. The serum precursors of plasma thromboplastin were normal.