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Low-salt diet increases mRNA expression of aldosterone-regulated transporters in the intermediate portion of the endolymphatic sac

  • Ion channels, receptors and transporters
  • Published:
Pflügers Archiv - European Journal of Physiology Aims and scope Submit manuscript

Abstract

The endolymphatic sac is a small sac-shaped organ at the end of the membranous labyrinth of the inner ear. The endolymphatic sac absorbs the endolymph, in which the ion balance is crucial for inner ear homeostasis. Of the three sections of the endolymphatic sac, the intermediate portion is the center of endolymph absorption, particularly sodium transport, and is thought to be regulated by aldosterone. Disorders of the endolymphatic sac may cause an excess of endolymph (endolymphatic hydrops), a histological observation in Meniere’s disease. A low-salt diet is an effective treatment for Meniere’s disease, and is based on the assumption that the absorption of endolymph in the endolymphatic sac abates endolymphatic hydrops through a physiological increase in aldosterone level. However, the molecular basis of endolymph absorption in each portion of the endolymphatic sac is largely unknown because of difficulties in gene expression analysis, resulting from its small size and intricate structure. The present study combined reverse transcription-quantitative polymerase chain reaction and laser capture microdissection techniques to analyze the difference of gene expression of the aldosterone-controlled epithelial Na+ channel, thiazide-sensitive Na+-Cl− cotransporter, and Na+, K+-ATPase genes in the three individual portions of the endolymphatic sac in a rat model. A low-salt diet increased the expression of aldosterone-controlled ion transporters, particularly in the intermediate portion of the endolymphatic sac. Our findings will contribute to the understanding of the physiological function of the endolymphatic sac and the pathophysiology of Meniere’s disease.

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All data generated or analyzed during this study are included in this published article and its supplementary information file.

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Funding

This work was supported by Grants-in-Aid for Scientific Research from the Japan Society for the Promotion of Science (#21K09634 to TM).

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Author notes

  1. Ai Matsubara and Takenori Miyashita contributed equally to this work.

Authors and Affiliations

  1. Department of Otolaryngology, Faculty of Medicine, Kagawa University, Ikenobe 1750-1, Miki-cho, Kita-gun, Kagawa, 761-0793, Japan

    Ai Matsubara, Takenori Miyashita, Nozomu Mori & Hiroshi Hoshikawa

  2. Institute of Neuroscience, Kagawa School of Pharmaceutical Sciences, Tokushima Bunri University, Sanuki, Kagawa, Japan

    Kentaro Nakashima & Si-Young Song

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  1. Ai Matsubara
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  2. Takenori Miyashita
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  6. Hiroshi Hoshikawa
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Contributions

AM, TM, HH, and NM designed the study. AM, TM, and KN performed the experiments. KN and SYS contributed reagents and analytical tools. AM, TM, and KN analyzed the data. AM, TM, KN, and SYS wrote the manuscript. All authors read and approved the final manuscript.

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Correspondence to Ai Matsubara.

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The animal protocols used were approved by the Animal Care and Use Committee of Kagawa University. All experiments were performed in accordance with the NIH Guidelines for the Care and Use of Laboratory Animals.

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Matsubara, A., Miyashita, T., Nakashima, K. et al. Low-salt diet increases mRNA expression of aldosterone-regulated transporters in the intermediate portion of the endolymphatic sac. Pflugers Arch - Eur J Physiol 474, 505–515 (2022). https://doi.org/10.1007/s00424-021-02661-9

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