The AVPR2 gene provides instructions for making a protein known as the vasopressin V2 receptor. This receptor works together with a hormone called arginine vasopressin (AVP), which is sometimes also called antidiuretic hormone (ADH). The vasopressin V2 receptor is found in the kidneys in structures called collecting ducts, which are a series of small tubes that reabsorb water from the kidneys into the bloodstream.
The interaction between AVP and the vasopressin V2 receptor triggers chemical reactions that control the body's water balance. When a person's fluid intake is low or when a lot of fluid is lost (for example, through sweating), AVP is released from the brain, where it is produced and stored. In the kidneys, this hormone attaches (binds) to the vasopressin V2 receptor and directs the kidneys to concentrate urine by reabsorbing some of the water back into the bloodstream. When fluid intake is adequate, the brain releases less AVP. At these times, less water is reabsorbed into the bloodstream and the urine is more dilute.