This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Kidney, Subject name: Pharmacology
[{'content': 'Vasopressin decreases the volume of urine primarily by causing: \nSelect and explain. \nA. Decrease in glomerular filtration rate, B. Decrease in renal blood flow, C. Decrease in water permeability of descending limb of loop of Henle, D. Increase in water permeability of collecting duct cells', 'role': 'user'}, {'content': 'Answer: D \nExplanation: In the absence of ADH, collecting ducts are impermeable to water. ADH increases the exocytosis and decreases the endocytosis of water channels (aquaporins) in the collecting duct cells. This results in increase in permeability of collecting ducts to water.', 'role': 'assistant'}]