[Effect of energy metabolism on the ionic selectivity of the K+ center of the Na+/K+ pump in the skin of the frog].

The uptake of Rb+ and Tl+ in frog skin incubated in saline containing 86Rb and 204Tl was studied. The ratio of ouabain-sensitive influxes Tl+/Rb+ = 2. Inhibition of the unidirectional transport of Na+ by rotenone or by Tl+ was not accompanied by the total decrease in the ouabain-sensitive uptake of Rb+ and Tl+. A substantial number of the Na+/K+ pumps continued to operate to maintain the intracellular ion homeostasis. The Tl+/Rb+ ratio of the cation influxes via pumps of this group was about twice as high compared to the control values. A coexistence of the two forms of Na+/K+ pumps in frog skin epithelium was postulated. They differ in both ion selectivity and the source of energy (respiration or glycolysis). The Tl+/Rb+ ratio of the ouabain-insensitive fluxes seems to be independent of the energetic metabolism.