A local cochlear mechanism of endolymph volume regulation

Abstract

It is generally believed that endolymph volume is regulated, not by the cochlea, but by the endolymphatic sac. Acute changes of endolymph volume in anesthetized guinea pigs has been induced by perfusing hypertonic medium (400 mOsm/kg H2O) for 20 min through the perilymphatic spaces. During hypertonic perfusion, changes of endocochlear potential (EP), endolymph K level, and endolymph volume (using tetramethylammonium: TMA as a volume marker) were monitored using ion‐selective microelectrodes. The osmotically induced K increase appeared to be comprised of two components. The first, an increase due to the loss of water from endolymph was estimated from the recorded TMA changes. In addition, a second component existed representing a net addition of K to the endolymph. This component was closely correlated with the EP reduction during dehydration, which suggests the endolymph K increase may result from the admission of anions into endolymph. A mechanism that produces an increase in endolymph solutes when endol...