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 (Isc). The baseline Isc of Claudius' cells was measured in the perilymph-like control solution and the change of Isc after application of amiloride (10 μM) or uridine triphosphate (UTP, 100 μM). Results: A negative baseline Isc was observed in the control solution (–12.50 ± 3.95 μA/cm2, n = 8) and the addition of amiloride resulted in a decrease of Isc by 75.8%. The application of UTP, an agonist for P2Y purinergic receptors, led to a partial inhibition of Isc (by 38.2 ± 3.2%, n = 5), and subsequent addition of amiloride abolished the remaining Isc.