The Na-K-Cl cotransporters in the rat cochlea: RT-PCR and partial sequence analysis.

Nonsensory epithelial cells of the mammalian cochlea contribute to the production of the endolymph. The presence as well as the function of the Na-K-Cl cotransporter has been suggested, but not yet been proved. To identify the Na-K-Cl cotransporter isoforms expressed in the cochlea, mRNA was extracted from the cochlear lateral wall. After reverse transcription, resulting cDNA was amplified by polymerase chain reaction (PCR) with primers specific for Na-K-Cl cotransporter isoforms. In the rat cochlear lateral wall, mRNA homologous to the mouse bumetanide-sensitive Na-K-Cl cotransporter (mBSC2) was detected. These results suggest that the basolateral localization of the cotransporter in the marginal cell is involved in the secretory process of the endolymph.