Aquaporins selectively conduct water molecules in and out of the cell, while preventing the passage of ions and
other solutes. Known as water channels, they are
integral membrane pore proteins (1, 2).
Aquarporin 1 is a widely expressed water channel, found
in the basolateral and apical plasma membranes of the
proximal tubes, the descending loop of Henel and in the
descending portion of the vasa recta. Additionally it is
found in red blood cells, vascular endothelium,
gastrointestinal tract, sweat glands and lungs. It is not
regulated by vasopressin (3).