Studies on Cardiotoxin Isolated from Cobra Venom: I. Effects of Cardiotoxin on Contractility, Absolute Refractory Period, and Action Potentials of Cardiac Muscle. II. Identification of Cardiotoxin with Cobramine B, DLF, Toxin gamma and Cobra Venom Cytotoxin
Annual rept. no. 4, Oct 1968-Aug 1970
NATIONAL TAIWAN UNIV TAIPEI PHARMACOLOGICAL INST
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The effects of cardiotoxin on the contractility, absolute refractory period and action potential of cariac muscle have been studied in isolated left atrial preparations of rats and right ventricular strips of guinea-pigs respectively. The transmembrane potential of the guinea-pig ventricular muscle cell is irreversibly depolarized by cardiotoxin. The duration and overshoot of action potential are both decreased by cardiotoxin. Cardiotoxin, Cobramine B, the direct hemolytic factor DLF, toxin gamma and cobra venom cytotoxin are all the most basic polypeptides isolated from cobra venoms. Cardiotoxin affects various kinds of cells, causing irreversible depolarization of cell membrane. It also has a weak direct hemolytic activity on washed erythrocytes of the guinea pig, dog and cat, and shows cytopathic effects of stable tumor cell cultures HeLa, KB. Both the contracture-inducing and direct hemolytic activities of cardiotoxin can be potentiated by phospholipase A, and prevented by polyanions gangliosides, RNA and heparin. From these results, it is concluded that cobramine B, DLF, and possibly cobra venom cytotoxin and toxin gamma are all identical with cardiotoxin or at least may be grouped as isotoxins of cardiotoxin.