Akvaporiini2

Akvaporiini2, also known as aquaporin 2 (AQP2), is a water channel protein found in the kidneys of mammals. It plays a crucial role in regulating the body's water balance. AQP2 is primarily expressed in the principal cells of the collecting ducts, the final segment of the nephron responsible for concentrating urine.

The primary function of AQP2 is to facilitate the rapid passage of water across cell membranes. This process is essential for reabsorbing water from the filtrate back into the bloodstream, thereby concentrating urine and preventing dehydration. The activity of AQP2 is tightly regulated by the hormone vasopressin, also known as antidiuretic hormone (ADH). When vasopressin levels rise, typically in response to dehydration or increased blood osmolarity, it binds to receptors on the principal cells. This binding triggers a signaling cascade that leads to the insertion of AQP2 water channels into the apical membrane of the cells, increasing water permeability. Conversely, when vasopressin levels fall, AQP2 is removed from the membrane and stored in intracellular vesicles, reducing water reabsorption.

Mutations in the gene encoding AQP2 can lead to a form of nephrogenic diabetes insipidus, a condition characterized by the inability of the kidneys to concentrate urine, resulting in excessive thirst and urination. Understanding the function and regulation of AQP2 is vital for comprehending kidney physiology and for developing treatments for disorders of water balance.