Positive inotropic and antiarrhythmic actions of actodigin in dogs (1)

The effects of actodigin were studied in dogs with decreased cardiac contractility or atrail flutter. When injected at 30 min invervals into dogs with barbiturate-induced heart failure, actodigin caused a marked positive inotropic action of short duration. Actodigin's pronounced but fleeting effect appears to be related to the novel attachment of its steroid nucleus alpha to the carboxyl function in the lactone. Cardiac glycosides with a conventional beta linkage of the lactone ring to the steroid nucleus (e.g., AY-22,248) had positive inotropic actions which were both slower in onset and cumulative when injected every 30 min. Apparently because of its short duration of action, actodigin was not as cardiotoxic as its isomer, AY-22,248. Lastly, a sustained atrail flutter was induced by intercaval crush and faradic atrial stimulation. Both actodigin and ouabain converted this arrhythmia to normal sinus rhythm.