Cystic fibrosis transmembrane conductance regulator in the endolymphatic sac of the rat

Objective: Na+ and Cl- are dominant ions in the endolymphatic fluid in the endolymphatic sac and are important for volume regulation in the endolymphatic sac. An epithelial sodium channel (ENaC) and other Na+ transporters have been identified in the endolymphatic sac epithelia, and they are involved in the regulation of endolymph. Although the presence of Cl- channels in the endolymphatic sac epithelia has been speculated, no Cl- channels have been identified. In this study, we confirmed the expression of cystic fibrosis transmembrane conductance regulator (CFTR) in the endolymphatic sac by reverse transcriptase polymerase chain reaction (RT-PCR) and by immunohistochemical staining. Methods: Pure mRNA from endolymphatic sac epithelia was prepared using laser capture microdissection (LCM) and examined using RT-PCR. Localization of CFTR and ENaC in the endolymphatic sac was examined using immunohistochemistry. Results: mRNA of the CFTR was expressed in the endolymphatic sac. Immunohistochemical analysis showed the expression of the CFTR on apical side of the endolymphatic sac epithelia and co-localization with the ENaC. Conclusion: RT-PCR and immunohistochemistry were used to identify the expression of CFTR in the endolymphatic sac epithelia, which gives us a clue for understanding Cl- transport in the endolymphatic sac. These results suggest a pathway for Cl-, possibly through interaction with the ENaC, which may regulate the endolymph in the endolymphatic sac. (C) 2014 Elsevier Ireland Ltd. All rights reserved.