Potassium flux in the isolated perfused rabbit heart

¹ Department of Physiology, University of Minnesota, Minneapolis, Minnesota

The exchange kinetics of potassium in the isolated, perfused rabbit heart have been studied in relation to changes in heart rate, extracellular potassium and temperature. The intracellular potassium appeared to exist in at least two compartments, the relative size varying with the extracellular concentration of potassium. The change in the potassium flux between heart rates of 100 and 200 beats/min. was compared to a change in flux calculated on the basis of the theory proposed by Hodgkin and co-workers and electrical constants taken from the literature. The change in flux estimated from the experimental curves was somewhat smaller than that required by theory and a discussion of this result is given. The activation energy calculated for the total potassium flux into and from the cells was estimated to be from 3000 to 8000 cal/ mole and found to be a function of the potassium concentration in the perfusate.