VI. Potassium exchange in papillary muscles

Jon Goerke ¹ and Ernest Page ¹

¹ From the Biophysical Laboratory, Harvard Medical School, Boston.

Dr. Page's present address is the Department of Zoology, University of California at Los Angeles. His permanent address is Departments of Medicine and Physiology, University of Chicago. Dr. Goerke's present address is the University of California Medical Center, San Francisco.

The exchange of cell K with K⁴², J_K, has been measured in cat right ventricular papillary muscle under conditions of a steady state with respect to intracellular K concentration. Within the limits of the measurement, all of cell K exchanged at a single rate. Cells from small cats are smaller and have larger surface/volume ratios than cells from large cats. The larger surface/volume ratio results in larger flux values. J_K increases in an approximately linear manner as the external K concentration is increased twentyfold, from 2.5 to 50 mM, at constant intracellular K concentration. The permeability for K ions, P_K, calculated from the influx and membrane potential, remains very nearly constant over this range of external K concentrations. J_K is not affected by replacement of O₂ by N₂, or by stimulated contractions at 60 per minute, but K influx decreases markedly in 10^-5 M and 10^-8 M ouabain.

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