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
Vasopressin acts through which channels in collecting duct? 
Select and explain. 
A. Aquaporin 1, B. Aquaporin 2, C. GLUT-1, D. GLUT-4
B: Aquaporin 2
Answer: B: Aquaporin 2 
Explanation: Ans. B. Aquaporin 2a. Principal cells of collecting duct contain a regulated system of water channels antidiuretic hormone (ADH, also called arginine vasopressin, AVP).b. ADH controls permeability of these cells to water by regulating insertion of pre-formed water channels (aquaporin-2, AQP2) into apical membrane.