But what exactly the function of aldosterone? Well, aldosterone doesn't actually directly increase the flow of water from our collecting duct. What it does is it stimulates the production of sodium channels on the apical side of our epithelial cells. And the particular epithelial cells involved in this process are called principal epithelial cells. So if we produce more sodium channels on the apical side of the membrane, more sodium ions will be absorbed by the collecting duct. More sodium ions will travel out of our collecting duct and into our interstituent.