Effect of ouabain on potassium exchange in heart muscle mitochondria

¹ Radioisotope Service, Veterans Administration Hospital; and Department of Medicine, New York University College of Medicine, New York City

Potassium in the working frog ventricle exists in two physiological compartments and the more slowly exchanging compartment is influenced by the amount of work performed, ventricular failure and ouabain. In the present study, the exchange of potassium in mitochondria is investigated both in the control state and after exposure to ouabain, in order to determine whether mitochondria potassium represents the slowly exchanging compartment. Mitochondria potassium represents only 15% of the total ventricular potassium, while the slowly exchanging phase contains about 50%. Ouabain perfusion is associated with inhibition of entrance of potassium into the slowly exchanging ventricular phase, but no isolated specific effect on the mitochondria potassium is found. Alterations in mitochondria potassium directly reflect changes within the total ventricle. A fraction of mitochondria potassium is found to be inexchangeable under the conditions of the experiment. The results indicate that mitochondria potassium does not represent the major part of the slowly exchanging compartment.

Note:
With the Technical Assistance of George Thompson