Effects of Digitalis and Hypoxia on Potassium Transfer and Distribution in the Dog Heart

Abstract

The effects of moderately severe hypoxia and moderately large doses of digitalis on potassium kinetics and distribution in the left ventricle of the normal intact dog were studied after the apparent establishment of a new steady state. Digitalis and hypoxia, more so, caused reduction in interstitial-intracellular potassium transfer rates and rate constants, and modest to moderate reduction in cell and interstitial potassium. Hypoxia also caused marked increase in plasma-interstitial potassium exchange rate and rate constants apparently due to the increased coronary blood flow resulting from hypoxia. The effects of digitalis on ISF-ICF transfer are compatible with the thesis that a major action of digitalis is the partial inhibition of of potassium transfer into the myocardial cell. The results from the steady state hypoxia experiments show that aerobic metabolism is necessary for at least a considerable fraction of potassium transfer in the heart.