Na+-inhibitory sites of the Na+/H+ exchanger are Li+ substrate sites.

Amiloride-inhibitable Li+ influx in dog red blood cells is mediated by the Na+/H+ exchanger, NHE. However, there are substantial differences between the properties of Li+ transport and Na+ transport through the NHE. Li+ influx is activated by cell shrinkage, and Na+ influx is not, as we reported previously (Dunham PB, Kelley SJ, and Logue PJ.

Extracellular Na+ inhibits Na+/H+ exchange: cell shrinkage reduces the inhibition.

Na+/H+ exchangers (NHE) are ubiquitous transporters participating in regulation of cell volume and pH. Cell shrinkage, acidification, and growth factors activate NHE by increasing its sensitivity to intracellular H+ concentration. In this study, the kinetics were studied in dog red blood cells of Na+ influx through NHE as a function of external Na+ concentration ([Na+](o)).