Еndolymph composition: paradigm or inevitability?

摘要

This review is focused on the unusual composition of theendolymph of the inner ear and its function in mechanoelectricaltransduction. The role of K+ and Ca2+ in excitatory influx, thevery low Na+, Ca2+ and Mg2+ concentrations of endolymph,stereocilia structure of hair cells and some proteins involved inmechanosensory signal transduction with emphasis on auditoryreceptors are presented and analyzed in more details.An alternative hypothetical model of ciliary structure andendolymph with a ‘normal’ composition is discussed. It isconcluded that the unique endolymph cation content is morethan an energy saving mechanism that avoids disturbingcirculatory vibrations to achieve a much better mechanosensoryresolution. It is the only possible way to fulfil the requirementsfor a precise ciliary mechanoelectrical transduction in conditionswhere pressure events with quite diverse amplitudes andduration are transformed into adequate hair cell membranedepolarizations, which are regulated by a sensitiveCa2+-dependent feedback tuning.