Passive Transport of Water out of Cell by Aquaporin-1 Aquaporin-1 (AQP1) passively transports water across the plasma membrane according to the osmotic gradient. In the kidney AQP1 is expressed in endothelial cells of the vasa recta, the proximal tubule, and thin descending limb of Henle, where it functions to recover water from filtrate during urine formation. AQP1 is expressed in many other tissues, such as red blood cells, pancreas, and choroid plexus. AQP1 plays a role in forming cerebrospinal fluid. Authored: May, B, 2009-08-06 Edited: May, B, 2009-08-06 Pubmed11034202 Pubmed12801959 Pubmed1373524 Pubmed14514735 Pubmed14592814 Pubmed14701836 Pubmed1510932 Pubmed18202181 Pubmed3049610 Pubmed7678419 Pubmed9829975 Reactome Database ID Release 43432054 Reactome, http://www.reactome.org ReactomeREACT_23786 Reviewed: Beitz, E, 2010-06-24 Reviewed: Calamita, G, 2010-07-15 Reviewed: Mathai, JC, MacIver, B, 2010-07-31