Section 4: Mini-Symposium-1: Endolymph Regulation and Mechanism of Hydrops Low Frequency Pressure Changes May Participate in Endolymph Volume Regulation

Endolymph is truly unique among the extracellular body fluids, in more ways than we have previously appreciated. A number of established concepts associated with other fluids, such as the concept of “secretion” (i.e. the process of generating new fluid in volume), simply do not apply to endolymph. The high metabolic costs of endolymph generation have resulted in highly efficient homeostatic processes that avoid the need to discard fluid in volume. Instead, the ionic composition of endolymph is largely maintained by local ion transport processes, in which the major ions are actively recycled between perilymph and endolymph. This process of ion recycling occurs with negligible associated volume flow, and occurs in the absence of any physiologically-significant longitudinal endolymph flow in the cochlea.