The anti-coagulant properties of an extract from the venom sac of the oriental hornet

An extract from the venom sac of the oriental hornet inhibits the in vitro formation of thromboplastin and thrombin by human plasma and inactivates already formed tissue thromboplastin. The extract has a strong fibrinogenolytic and fibrinolytic activity when tested on purified human fibrinogen, but almost no lytic activity when tested on human plasma. The fibrinolysis is inhibited by soybean trypsin inhibitor as well as by human serum, presumably due to its anti-trypsin activity. Intravenous administration of the sac extract to dogs causes decreased clottability of the whole blood, or the recalcified plasma, and depresses prothrombin consumption and thromboplastin generation. There is a significant decline of the platelet count but a rather mild decrease of fibrinogen. All parameters tend to revert to normal after 2–3 hr. Intraperitoneal envenomation causes severe heparinemia with prolonged clotting, effects which can be reversed by the addition of protamin sulfate. The anticoagulant properties of the venom are abolished by heating at acid or alkaline pH and neutralized by anti-venom immune serum.