Positive Chronotropic and Inotropic Actions of New Antitumor Agent Adriamycin and Its Cardiotoxicity : Its Special References to Myocardial Contractile Force and the Change of the Transmembrane Action Potential

New antitumor antibiotic adriamycin, chemically glycoside linkage of the red pigmented aglycone and the water soluble aminosugar, has been clinically known to produce some electrocardiographic abnormalities such as sinus tachycardia, ST segment depression and the flattening of T wave, as its side effect. In order to clarify its genetic mechanism, isolated guinea pig heart perfused by Langendorff's technique was used and single shot of adriamycin into this preparation produced positive chronotropic and inotropic actions and the acceleration of the repolarization process manifested by the shortening of the duration of the membrane action potential, especially, the repolarization phase 2. This agent has lesser degree of acute accumulative effect in producing arrhythmia, as compared with the action of daunomycin. These effects were completely blocked by dl-propranolol.