Abstract

Atelopidtoxin is a new potent dialysable, water-soluble, nonprotein, nonsteroidal substance that has been isolated from the skin of the Panamanian frog, Atelopus zeteki. In the perfused bullfrog heart this toxin produces variable degrees of atrioventricular block and, at higher concentrations, ventricular asystole, without affecting atrial rhythm. In dogs, i.v. administration of atelopidtoxin produces almost immediately sustained hypotension with compensatory tachycardia. Intra-atrial and intraventricular bipolar leads were used to study the electrocardiographic changes produced by this toxin in anesthetized dogs. These changes include delayed conduction through the atrioventricular node and aberrant conduction through the Purkinje system, indicated by marked changes in the cavitary R and S waves. Disturbances of rhythm consist of ectopic ventricular depolarizations leading to terminal ventricular fibrillation. Atrial function is not affected. These effects of atelopidtoxin are not modified by the antiarrhythmic agents, procainamide and diphenylhydantoin. Epinephrine antagonizes the hypotension produced by atelopidtoxin in dogs and reverses the atrioventricular block in frog heart and income instances in the dog. The toxin has a negative inotropic effect in the heart-lung preparation. It has no effect on the action potential of desheathed frog sciatic nerve or on neuromuscular transmission in the dog at concentrations that produce marked cardiovascular effects. Atelopidtoxin is a new and unique cardiotoxin deserving further study.