This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Physiology
[{'content': 'The Principal site of absorption of sodium is \nSelect and explain. \nA. Proximal convoluted tubule, B. Distal convoluted tubule, C. Loop of Henle (thick portion), D. Collecting duct', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Other than at thin descending limb of the loop of Henle, all other sites of tubule Na+ are reabsorbed by various mechanisms. \n-\xa0\xa0\xa0\xa0\xa0\xa0\xa0 Proximal tubule- 60-70%\n\nNa+- H+ exchange\nNa+- Glucose co-transport\nNa+- amino acid co-transport\nNa+ unitransport\n\n-\xa0\xa0\xa0\xa0\xa0\xa0\xa0 The thick ascending limb of the loop of Henle - 30%\n\nNa+- 2Cl-- K+ co-transport\n\n-\xa0\xa0\xa0\xa0\xa0\xa0\xa0 Early distal tubule- 7%\n\nNa+- Cl- co-transport\n\n-\xa0\xa0\xa0\xa0\xa0\xa0\xa0 Late distal tubule and collecting duct - 3%\n\nENaC channels', 'role': 'assistant'}]