Membrane potentials in K-deficient muscle

¹ Departments of Medicine and Physiology, Western Reserve University School of Medicine, Cleveland, Ohio

Thirteen K-deficient and 14 pair-weighed control rats have been studied after 2 weeks on the experimental diets. Resting membrane potentials of skeletal muscle were measured immediately before killing the rats for plasma and muscle analysis. From the analytical data for Na, K, Cl, basic amino acids (BAA), and from plasma and intracellular pH studies in another series of rats studied concurrently, equilibrium potentials for Na, K, H, and BAA have been calculated and those from K-deficient animals compared with controls. The membrane potential is less negative in K depletion. All ions except K are closer to equilibrium across the K-deficient muscle membrane than they are in control tissue, provided BAA are considered to penetrate the membrane as univalent cations. A decrease in the fractional conductance of K and an increase in the fractional conductances of the other cations in K deficiency are inferred. The H⁺ ion is not in thermodynamic equilibrium across the membrane. The high concentration of BAA in K deficiency could be due to failure of a "BAA pump" or to a change in the passive permeability to the various ionic species of these zwitter ions.