This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Kidneys and Body Fluids, Subject name: Physiology
[{'content': 'A luminal cell membrane Na+ channel is the main pathway for Na+ reabsorption in: \nSelect and explain. \nA. Proximal tubule cells, B. Thick ascending limb cells, C. Distal convoluted tubule cells, D. Collecting duct principal cells', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Ans D. Collecting duct principal cellsNa+ reabsorption by collecting duct principal cells occurs via a Na+ channel called ENaC (epithelial sodium channel). Na+ reabsorption in proximal tubule cells is coupled to transport of solutes via cotransport (e.g., Na-glucose) and antiport (e.g., Na+/H+ exchanger) mechanisms. Na+ reabsorption in the thick ascending limb involves a Na-K-2Cl cotransporter and, in the distal convoluted tubule, a Na-Cl cotransporter. Collecting duct intercalated cells are primarily concerned with acid-base, not Na+, transport.', 'role': 'assistant'}]