Na+ transport occurs across many epithelial surfaces and plays a key role in regulating salt and water absorption. The molecular pathway underlying this Na+ transport is the epithelial Na channel (ENaC), which is strictly determined by a variety of hormones like aldosterone, ADH and glucocorticoids. In this study, we found that stimulation of either aldosterone or dexameth- asone (Dex) distributed ENaC channel on the apical membrane of mouse cortical collecting duct cells (M1). In the single channel recordings from excised membrane, high density ENaC was found in the cell with a dome shape by the treatment of either dex or aldosterone. However, low active ENaC was revealed in intact cells treated with dex, when compared to cells treated with aldosterone. Only 5.84% of cells treated with dex containing ENaC exhibited ENaC current transition in the cell-attach recording, whereas 40% of cells treated with aldosterone containing ENaC exhibited ENaC current transition. ENaC currents appeared rapid rundown within 5 min-utes since formation of inside-out configuration in cells treated with aldosterone but not with dex. SKF-525A, a general antagonist of CYP, failed to significantly enhance ENaC activity in intact cells treated with dex, but EGTA, which deforming the cells, increased the ENaC activity in the cells treated with dex. PTX, an antagonist of G-protein, reversed the effect of aldosterone on number of active ENaC in intact cells. Based on our obser-vation, we concluded that there are different mechanisms in regulation of ENaC activity be-tween stimulation of aldosterone and glucocor-ticoids. The activation of G-protein is required to maintain the activity of ENaC in the collecting ducts.
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