Cellular localization of rat Isk protein in the stria vascularis by immunohistochemical observation

A novel rat membrane protein, termed Isk protein, that exhibits a voltage-dependent potassium channel activity was first reported through molecular cloning combined with an electrophysiological assay (Takumi et al., 1988). In the present study, we made an attempt to identify the cellular localization of the rat Isk protein in the stria vascularis using two types of antibodies that specifically react with the distinct parts of the rat Isk protein. Immunohistochemical analysis showed that the rat Isk protein was present only on the endolymphatic surface of the marginal cell. The possibility that the Isk protein is involved in potassium permeation in the luminal membrane of the marginal cell will be also discussed.