V2, a G protein coupled receptor, also called arginine vasopressin receptor 2 (AVPR2), is a receptor for neurohypophyseal peptide [Arg8]-vasopressin. It is expressed in the kidney tubule, mainly in the membrane of cells of the distal convoluted tubule and collecting ducts, in fetal lung tissue and lung cancer. In the kidney, V2 receptor responds to vasopressin and activates mechanisms that concentrate urine and maintain water homeostasis in the body. Loss of function of the V2 receptor results in nephrogenic diabetes insipidus. The primary transduction mechanism is via adenylate cyclase stimulation to raise intracellular cAMP levels. Selective antagonists for V2 can be used to treat hyponatremia.