Ion flow in stria vascularis and the production and regulation of cochlear endolymph and the endolymphatic potential

This paper reviews some of what is known about ion transport through the cells of the mammalian stria vascularis, and discusses how the endolymph and endocochlear potential in scala media are produced by the stria’s main cell types. It discusses the role of each cells’ ion transport proteins from an engineering perspective, and the advantages and disadvantages in using the different transport proteins in the different cells to perform their different roles. To aid this discussion, the use of spreadsheet analysis in the modelling of ion transport in single cells and homogenous epithelia is outlined, including the current-voltage (IV) characteristics of the three main categories of transport proteins (pores, ports and pumps), and the constraint equations that apply under various conditions (the voltage or ionic steady states in the open- and closed-circuit conditions). Also discussed are the circulation of K+ within the cochlea, and the chloride, salt and water balance of scala media and stria vascularis, and what transport processes may be required to maintain such a balance.

► Ion transport proteins and cell topology in stria vacularis are summarised.
► Regulation of endocochlear potential and endolymph composition are discussed.
► Spreadsheet analysis of epithelial transport is described.