Aquaporins: transmembrane channels that allow rapid movement of water across plasma membrane in various cells--erythrocytes proximal renal tubule cells table 12-3 Aquaporins Aquaporin Roles and location AQP-1 Fluid reabsorption in proximal renal tubule secretion of aqueous humor in eye and cerebrospinal fluid in central nervous system; water homeostasis in lung AQP-2 Water permeability in renal collecting duct (mutations produce nephrogenic diabetes insipidus) AQP-3 Water retention in renal collecting duct AQP-4 Reabsorption of cerebrospinal fluid in central nervous system regulation of brain edema AQP-5 Fluid secretion in salivary glands, lachrymal glands, and alveolar epithelium of lung TIP Water uptake by plant vacuole, regulating turgor pressure Source: King, L.S.& Agre, P(1996)Pathophysiology of the aquaporin water channels Annu. Rev. Physio/ 58, 619-648Aquaporins: transmembrane channels that allow rapid movement of water across plasma membrane in various cells—erythrocytes, proximal renal tubule cells