Ouabain cardiotoxicity, a reassessment of methodology

The capacity of ouabain (1 mug/kg/min and 2 mug/kg/min) to induce cardiotoxicity was explored in control cats and cats after spinal cord transection. In cats receiving 1 mug/kg/min, a higher dose of ouabain was needed to produce lethal arrhythmias in spinal cats compared to intact cats. However, in cats receiving 2 mug/kg/min, there was no difference in dose to death between intact and spinal cats. At death, the serum level and ventricular contents of ouabain was higher in animals with spinal cord transection regardless of the rate of ouabain infusion. Thus it appears that determination of the myocardial tissue digitalis concentration more accurately reflects the state of digitalis sensitivity than the administered dose. Additionally, seemingly paradoxical findings with regard to dose are explicable when serum and tissue concentration are simultaneously evaluated.