Sources of energy for the transport of potassium and sodium across the membrane of the Ehrlich mouse ascites tumor cell.

Abstract

Abstract Evidence has accumulated in support of two hypotheses to explain the linkage between metabolism and the transport of electrolytes across cell membranes. In one, an ATPase, sensitive to sodium and potassium, converts the free energy of ATP into the directed movements of sodium and potassium. In the other, the free energy of ATP may be diverted into directional movements of electrons along a redox chain coupled to the movement of ions. To assess the relative contributions of each in the Ehrlich mouse ascites tumor cell, the source of ATP from respiration was blocked with antimycin A, amytal, and oligomycin, all of which reduced respiration, and with 2,4-dinitrophenol, which stimulated oxygen consumption and electron flow. Glucose and the glycolytic pathway were used to maintain ATP levels in the cell in the presence of these inhibitors. Potassium and sodium transport under these conditions were studied with isotopic and chemical methods. The results of these studies continue to show that ATP content must still be at normal levels in the ascites tumor cell to maintain ion fluxes and content. However, it was possible to demonstrate, also, that fluxes could be reduced and the ion content of the cell altered even though ATP levels were normal. The inhibitor, oligomycin, was most effective and the results would indicate that some high-energy intermediate step, sensitive to oligomycin, exists between the energy of ATP and ion transport. The intermediate may be a step in oxidative phosphorylation occurring at a mitochondrial site or part of a complex occurring in the cell membrane.