Epithelial Na⁺ channel (ENaC) expression in obstructive sialadenitis of the submandibular gland

Background and objectives: The epithelial sodium channel (ENaC) has a critical role in the control of sodium balance, blood volume, blood pressure and viscosity of extracellular water. In submandibular gland disease, viscosity of the saliva plays an important role in the pathophysiology. However, there has been little study into the relationship between expression of ENaC and obstructive sialadenitis. The aim of this study was to elucidate the ENaC expression in excretory duct obstruction of the submandibular gland. Materials and methods: Seven-week old male Sprague-Dawley 12 rats were enrolled in the study. The rats were decapitated and histological changes of the submandibular gland tissue examined on days 0, 1, 3, 7, 14 and 21 after submandibular gland duct ligation. The expression of ENaC mRNA in the submandibular gland tissue was tested by reverse transcriptase-polymerase chain reaction (RT-PCR). Quantitative analysis of the ENaC protein was performed through Western blotting and tissue localization of the protein was performed by immunohistochemical staining. Results: By real time RT-PCR, the expression of ENaC (α, β, γ) mRNA increased after ligation of the submandibular gland duct. α and γ ENaC mRNA expression began to increase after 1 day. But β ENaC mRNA expression began to increase significantly after 14 days. The increase of ENaC mRNA expression lasted for 3 weeks. The expression of ENaC (α, β, γ) protein was identified by Western blotting analysis, and ENaC protein was localized in ductal epithelial cells by immunohistochemistry. Conclusion: The expression of ENaC (α, β, γ) was increased by excretory duct ligation of the submandibular gland in rats and ENaC was considered to have a certain role in the pathogenesis of obstructive sialadenitis.