Regulation of sodium transport in the inner ear

► The epithelial cells bounding the lumen of the inner ear maintain low endolymphatic [Na+]. ► Low [Na+] supports normal hearing and balance. ► Endolymphatic Na+ is taken up by the cells through apical Na+-permeable ion channels. ► Cytosolic Na+ is discharged into perilymph by the basolateral Na+,K+-ATPase. ► Na+ absorption is regulated by glucocorticoid and purinergic signal pathways.