Volume regulation by Amphiuma red blood cells: Strategies for identifying alkali metal/H⁺ transport

The regulation of cell volume in response to anisotonic media, and in a broader perspective electroneutral alkali/metal H⁺ exchange transport, are currently areas of general interest to transport physiologists. In this paper I outline the basic features of volume-sensitive ion fluxes as studied with Amphiuma red blood cells. As has been shown in previous studies the alkali metal ion fluxes that are responsible for volume regulation by these cells are electroneutral by virtue of obligatory counter coupling with H⁺. The criteria for establishing the existence of electroneutral alkali metal/H⁺ exchange in these cells will be reviewed and expanded on. In the process, behavior and phenomena consistent with, as well as those unique to, electroneutral alkali metal/H⁺ exchange will be introduced, illustrated with experimental data, and discussed. Finally, based on thermodynamic considerations, kinetic behavior will be evaluated in terms of electroneutral alkali metal/H⁺ transport.