Intracellular and extracellular ion content of the endolymphatic sac

The Cl- activity in the endolymph of the endolymphatic sac and in the cochlear duct was measured with Cl- sensitive double-barreled microelectrodes. The Cl- activity in the endolymphatic sac fluid was lower than in the cochlear duct. A small, positive, DC potential was recorded in the endolymphatic sac. During anoxia, the DC potential decreased while the Cl- activity in the endolymphatic sac increased. The K/Na ratio in the epithelial cells and subepithelial tissue of endolymphatic sac was measured using the LAMMA technique. The K/Na ratio in the epithelial cells decreased after ethacrynic acid injection (60 mg/kg i.v.). These findings suggest that chloride in the endolymphatic sac is actively transported inward and outward.