Studies on Cardiotoxin and Vasoactive Substance Releasing Component(s) of Cobra Venom. Comparison of Hemodynamic Effects of Cardiotoxin with those of Cobra Venom
Annual rept. no. 2, Jun 1967-Jun 1968
NATIONAL TAIWAN UNIV TAIPEI PHARMACOLOGICAL INST
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The effects of cardiotoxin on the cardiovascular system has been studied in comparison with those of crude venom of Formosan cobra. The intravenous injection of cardiotoxin 1.0 mgkg usually produces an immediate rise in systemic arterial pressure, followed by a progressive decline leading to cardiac arrest, whereas a precipitous fall in systemic arterial pressure is usually observed with crude venom 0.5 - 1.0 mgkg. A very marked increase in both pulmonary artery pressure and pulmonary vascular resistance is produced following the injection of crude venom, whereas the increase is far less conspicuous with cardiotoxin. Cardiac output as well as stroke volume is decreased by both crude venom and cardiotoxin. Ventricular contractile force is depressed by both crude venom and cardiotoxin, usually preceded by an initial augmentation of varying duration. Abnormal ECG changes are observed with cardiotoxin as well as crude venom. V. cava pressure is increased with crude venom probably as a result of dilatation of the right heart, whereas no appreciable change in caval pressure is found with cardiotoxin unless cardiac functions are seriously impaired at a later stage. Total peripheral resistance is increased and femoral artery flow decreased by cardiotoxin. It is concluded that cardiotoxin is responsible for the initial pressor response as well as the cardiotoxic effects of cobra venom leading to cardiac arrest.