EFFECTS OF ANCROD, COAGULATING ENZYME FROM VENOM OF MALAYAN PIT VIPER (AGKISTRODON-RHODOSTOMA) ON PROTHROMBIN AND FIBRINOGEN METABOLISM AND FIBRINOPEPTIDE-A RELEASE IN MAN

Abstract

The action of ancrod on fibrinogen and prothrombin metabolism was studied in 6 healthy individuals by the use of 131I-fibrinogen and 125I-prothrombin and by measurement of blood levels of fibrinopeptide A. Two untreated healthy controls were studied at the same time. Rapid defibrinogenation occurred during the initial 3 h ancrod infusion, and fibrinogen levels were maintained near 0 throughout the study. Large quantities of non-thrombin-clottable TCA[trichloroacetic acid]-precipitable 131I material could be demonstrated in the circulation, reaching a maximum 3-6 h after ancrod infusion and clearing with a half-life of 6 h. Gel filtration of 6 h plasmas demonstrated the presence of complexes larger than fibrinogen, as well as degradation products of fibrinogen-fibrin. Prothrombin concentration and metabolism were unchanged by ancrod treatment. Fibrinopeptide A levels in the ancrod group were > 4000 ng/ml during the initial defibrinogenation, declined to > 80 ng/ml, and then increased to high levels after 3 days. These studies provide explanations of previous observations concerning the specificity of ancrod. Rapid clotting of fibrinogen and dissolution of fibrin can occur in vivo without recruitment of the classic coagulation mechanism.