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Expression of an inwardly rectifying K + channel, Kir5.1, in specific types of fibrocytes in the cochlear lateral wall suggests its functional importance in the establishment of endocochlear potential
Author(s) -
Hibino Hiroshi,
HigashiShingai Kayoko,
Fujita Akikazu,
Iwai Kaori,
Ishii Masaru,
Kurachi Yoshihisa
Publication year - 2004
Publication title -
european journal of neuroscience
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.346
H-Index - 206
eISSN - 1460-9568
pISSN - 0953-816X
DOI - 10.1111/j.1460-9568.2004.03092.x
Subject(s) - spiral ligament , endocochlear potential , endolymph , fibrocyte , chemistry , anatomy , cochlear duct , perilymph , cochlea , biology , organ of corti
Cochlear endolymph contains 150 m m K + and has a highly positive potential of ≈ +80 mV. The specialized ionic composition and high potential in endolymph are essential for hearing and maintained by circulation of K + from perilymph to endolymph through the cochlear lateral wall. Various types of K + channel such as Kir4.1 and KCNQ1/KCNE1 are expressed in stria vascularis of the lateral wall and play essential roles in K + circulation. In this study, we examined a distribution of another K + channel, Kir5.1, and found it specifically expressed in the spiral ligament of the cochlear lateral wall. Specific immunoreactivity for Kir5.1 was detected in type II, IV and V fibrocytes of the ligament and spiral limbus, all of which are directly involved in K + circulation. Kir5.1 was not found in either type I or III fibrocytes. Although Kir5.1 assembles with Kir4.1 to form a functional Kir channel in renal epithelia and retinal Müller cells, double‐immunolabelling revealed that they were expressed in distinct regions in the cochlea lateral wall, i.e. Kir4.1 only in stria vascularis vs. Kir5.1 in spiral ligament. During development, the expression of Kir5.1 subunits started significantly later than Kir4.1 and was correlated with the ‘rapid’ phase of the elevation of endocochlear potential (EP). Kir5.1 and Kir4.1 channel‐subunits may therefore play distinct functional roles in K + circulation in the cochlear lateral wall.