ABSTRACT
BACKGROUND AND OBJECTIVES: Nucleotide binding to purinergic P2Y receptors contributes to the regulation of fluid and ion transport in the middle ear epithelial cells. Here, we investigated the regulatory mechanism of the P2Y2 receptor agonist, uridine-5'-triphosphate (UTP), on Cl- transport in cultured normal human middle ear epithelial (NHMEE) cells. MATERIALS AND METHOD: Electrophysiological measurements were performed in monolayers of cultured NHMEE cells. Short circuit currents (Isc) were measured from the cells mounted in Ussing chambers under various conditions. RESULTS: Apical addition of UTP in presence of amiloride evoked a transient rise and a sustained response in Isc due to Cl- efflux. Application of different Cl- channel blockers to the apical side of the cells significantly decreased UTP-induced Isc. Niflumic acid (NFA), a known blocker of Ca(2+)-activated chloride channels (CACC), and CFTRinh172, a selective inhibitor of cystic fibrosis transmembrane conductance regulator (CFTR), partially inhibited the UTP-induced Cl- secretion, respectively. CONCLUSION: Cl- transport across the airway epithelia plays a predominant role in regulating airway hydration. In this study, UTP is shown to increase both CACC and CFTR-dependent Cl- secretion in NHMEE cells, suggesting their role in fluid and ion transport in the middle ear epithelium.