—Phospholipids of guinea‐pig inner ear tissues were labelled in vivo by perilymphatic perfusion of the cochlea with [32P]orthophosphate or myo‐[3H]inositol. After 20‐40 min the most highly labelled 32P‐lipids were phosphatidylinositol phosphate and diphosphate. Incorporation of [3H]inositol proceeded in the order phosphatidylinositol > phosphatidylinositol phosphate > phosphatidylinositol diphosphate. After treatment of animals with neomycin for 3 weeks, 32P‐incorporation into phosphatidylinositol diphosphate, but not into other lipids, was significantly decreased in the preparations of the organ of Corti and stria vascularis. In homogenates of inner ear tissues, the labelling of the polyphosphoinositides by [γ‐32P]ATP was increased and the hydrolysis of these lipids was blocked in the presence of 10−4m‐neomycin. Neomycin also competitively inhibited the binding of 45Ca2+ to homogenates of these tissues.

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.

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