Reversal of Ouabain and Acetyl Strophanthidin

sponse to additionally added digitalis, and relation of antibody effects on digitalis-induced automaticity and contracture to reversal of inotropy. Specific antibody (but not control antibody) in 1.1-1.5-fold molar excess over cardioactive steroid concentrations blocked positive inotropic effects of ouabain and acetyl strophanthidin, and gradually reversed established contractile effects of these agents with a mean time for half-reversal of ouabain-induced inotropy of 124±6 (SEM) min and 37±3 min for half-reversal of acetyl strophanthidin-induced inotropy. Papillary muscles from cats with right ventricular failure induced by chronic pulmonary artery constriction responded similarly. Both normal and failing muscles returned to but not below levels of contractility existing before cardioactive steroid exposure, and time for half-reversal of inotropy by antibody was significantly shorter than time for half-reversal after removal of ouabain or acetyl strophanthidin by muscle bath washout alone. Presence of ouabainor acetyl Dr. Smith is an Established Investigator of the American Heart Association. Received for publication 7 November 1973 and in revised form 18 January 1974. strophanthidin-antibody complex did not alter the myocardial contractile response to subsequently added cardioactive steroids. Spontaneous automaticity occurring as a toxic response to ouabain or acetyl strophanthidin in eight muscles was rapidly reversed by specific antibody at a time when positive inotropic effects were still fully manifest. Early contracture was also reversed by specific antibody. These studies provide further support for the concept that cardiac glycoside-specific antibodies are capable of reversing established cellular effects of cardioactive steroids.