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. Now, as a result of that, water will basically follow because if we have more sodium ions flowing out, the concentration here will increase, and so water will follow as a result. And that's exactly what aldo steroid does. So as sodium moves out of the lumen and into the interstituum, the surrounding tissue around the collecting dug, it also brings water along for the ride.