The Aquaporin family consists of 13, small and hydrophobic proteins named AQP0 to AQP12. They are expressed in a subset of epithelia that have 10 to 100- fold higher capacities for water permeation such as kidney tubules and red blood cells. These channels facilitate osmotically driven water transport and are divided into two groups based on their permeability characteristics: AQP1, AQP2, AQP4, AQP5 and AQP8 are considered primarily as water selective channels. AQP3, AQP7, AQP9 and AQP10 transport water as well as glycerol and are also called Aquaglyceroporins.