Atrial natriuretic peptide reduces the α-subunit of the epithelial sodium channel mRNA expression in the mouse stria vascularis

Atrial natriuretic peptide (ANP) is extensively expressed in the cochlea, including the strial vascularis (StV). ANP may participate in the regulation of the water-electrolyte balance. However, the functional significance of ANP in the cochlea is less understood and little is known regarding the exact mechanisms. Studies suggest that the epithelial sodium channel (ENaC) is important for regulating sodium transport across epithelia. ENaC may be involved in the clearance of endolymphatic Na⁺ and maintenance of a K-rich and Na-poor composition in the endolymph. Whether ANP has a regulatory effect on the Na⁺ channel in the StV remains unknown. The aim of the present study was to evaluate whether ANP affects the expression of the α-subunit of the ENaC (α-ENaC) mRNA in the mouse StV, using the reverse transcription-quantitative polymerase chain reaction (RT-qPCR) technique. The mouse StV tissues were incubated with 10^-6 mol/1 ANP for different times (2, 6, 12, 24 and 48 h) and were subsequently harvested. α-ENaC mRNA was extracted for RT-qPCR analysis of the expression. The study demonstrated the existence of α-ENaC in the mouse StV. Tissues treated with ANP (10^-6 mol/1) showed a significant reduction in α-ENaC mRNA expression (n=3, P<0.05). A maximum effect was reached at 2 h after treatment. The present results indicate that ANP may regulate cochlear ion transport and endolymph fluid balance in the inner ear via reducing expression of the α-ENaC mRNA in the mouse StV.