K+ influx components in ascites cells: The effects of agents interacting with the (Na++K+)-pump

Several agents known to interact with the (Na++K+)-pump were tested for their effects on the components of steady-state K+ flux in ascites cells.86Rb+ was used as a tracer for K+, and influx was differentiated into a ouabain-inhibitable “pump” component, a Cl−-dependent and furosemide-sensitive “exchange” component, and a residual “leak” flux. All agents tested (ouabain, quercetin, oligomycin, phosphate) affected both the “pump” flux and the Cl−-linked flux. These findings suggest a linkage between the activity of the Na/K ATPase and the Cl−-dependent K+ exchange flux. In the discussion we point out that the mechanism of this linkage could be direct; e.g., Cl−-dependent exchange may represent a mode of operation of the Na/K ATPase. However, data from this and other systems tend to suggest an indirect linkage between the Na+ pump and a KCl symporter, perhaps via a change in the level of intracellular ATP.