Identification of the direct lytic factor from cobra venom as cardiotoxin

Abstract

The most basic polypeptide in cobra ( Naja naja) venom was isolated by chromatography on CM Sephadex columns as a chromatographically and electrophoretically uniform substance. This polypeptide comprises the total, rather low, direct lytic activity and also the total, very strong, cardiotoxic activity of the cobra venom. It should, therefore, be named ‘cardiotoxin’ rather than ‘direct lytic factor’ (DLF). Cardiotoxin and phospholipase A display a synergistic action in vitro. To determine whether this is also true in vivo, cardiotoxin was injected into dogs and monkeys by itself and together with phospholipase A. Furthermore, because of the interesting parallelisms of cobra and bee venom, analogous experiments with the polypeptides from bee venom were undertaken. The results showed that the lethality of cardiotoxin from cobra venom as well as that of melittin from bee venom increases strongly by additional injection of phospholipase A either before or after that of cardiotoxin or melittin. The second injection is the decisive one in the mechanism of death; if it consists of phospholipase A, the animals die due to respiratory failure, otherwise death is due to ventricular fibrillation.