This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Renal physiology, Subject name: Physiology
Aquaporin channel mediated through ADH 
Select and explain. 
A. GLUT, B. Aquaporin 1, C. Aquaporin 2, D. Aquaporin 3
C: Aquaporin 2
Answer: C: Aquaporin 2 
Explanation: Vasopressin * Vasopressin - secreted by suprachiasmatic nuclei of hypothalamus and transpoed to posterior pituitary * Biologic half life - 18 min * Vasopressin receptors:- V1A and V1B V1A and V1 B:- * G protein coupled receptor that acts phosphatidylinositol hydrolysis to increase intracellular Ca++ concentration * V1A - mediate vasoconstrictor effect * V1B - also called V3 receptors- specific to anterior pituitary - mediate secretion of ACTH V2 receptor:- * G protein coupled receptor that acts through Gs to increase cAMP * Antidiuretic action * Mechanism of action - inseion of aquaporin 2 into the apical membranes of the principal cells of collecting duct. Factors affecting vasopressin secretion Ref:- Ganong's Review of Medical Physiology 25th ed; pg num:- 696