Movement of Inorganic Ions across the Membrane of Striated Muscle

The unidirectional fluxes of sodium, chloride, and potassium across the membrane of striated muscle cells are described under a number of experimental conditions. The results are compared with the predicted behavior of simple membranes. With the possible exception of chloride, it is concluded that the movements of these ions cannot be described without postulating variable permeabilities or a variable number of `carriers' or `sites' in the membrane.