Alteration of the effects and distribution of ouabain by spinal cord transection in the cat

The dose, serum level and tissue content of ouabain needed to produce cardiotoxicity were examined in allobarbital urethan anesthetized cats with and without spinal cord transection. At the time of ventricular fibrillation, the dose and serum level of ouabain were significantly higher in animals with spinal cord transection. The concentration of ouabain was elevated in atrium, ventricle and most other tissues of the spinal animals. Only the renal ouabain concentration exceeded that of the myocardium. Although the lower blood pressure observed in the spinal animals might reduce the efficiency of ouabain delivery to the myocardium, it could not explain the higher myocardial tissue requirements for cardiotoxicity. Heart rate, which might influence the rate of ouabain uptake by the myocardium, similarly does not adequately account for the observed changes in sensitivity. These data are consistent with an important role for the nervous system in the genesis of cardiotoxicity by ouabain.