Na⁺ absorption by Claudius' cells is regulated by purinergic signaling in the cochlea

Abstract

Conclusion: Claudius' cells absorb Na⁺ through the amiloride-sensitive epithelial sodium channel (ENaC). Transepithelial ion transport through ENaC and possibly a Cl^– secretory pathway is regulated by P2Y purinergic signaling. Objectives: The purpose of this study was to investigate ion transport in Claudius' cells and its purinergic regulation. Methods: Young adult Sprague–Dawley rats and gerbils were studied. The Claudius' cell layer on the basilar membrane was dissected from the basal turn of the cochlea. A voltage-sensitive vibrating probe was used to measure transepithelial short circuit current (I_sc ). The baseline I_sc of Claudius' cells was measured in the perilymph-like control solution and the change of I_sc after application of amiloride (10 μM) or uridine triphosphate (UTP, 100 μM). Results: A negative baseline I_sc was observed in the control solution (–12.50 ± 3.95 μA/cm², n = 8) and the addition of amiloride resulted in a decrease of I_sc by 75.8%. The application of UTP, an agonist for P2Y purinergic receptors, led to a partial inhibition of I_sc (by 38.2 ± 3.2%, n = 5), and subsequent addition of amiloride abolished the remaining I_sc.

Keywords::

• Epithelial sodium channel
• purinergic receptor
• voltage-sensitive vibrating probe
• rat
• gerbil

Acknowledgments

This research was supported by the Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education, Science and Technology (2011-0005640) and by National Institutes of Health grant R01-DC00212.

Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.