Aquaporin's Secrets Peter Agre, M.D. Photo by Norman Watkins Plants may have as many as 50 aquaporins.
Animals likely have fewer.
Aquaporin's Secrets By Marjorie Centofanti Peter Agre never imagined, when he stumbled across a mysterious new protein, that he had found the answer to the age-old mystery about how the body regulates water. What's surprising, however, is how long it's taken to figure out how cells handle water. That is, how they move all that fluid in and out of the cell-enclosing membrane. For years, scientists assumed that H2O, a small molecule, just slips by the specialized fats, proteins and cholesterols that make up cell membranes, gently diffusing to one side or the other according to the principles of osmosis. Yet physiologists pointed to certain cases that defy that explanation - the kidneys, for example, where water cruises through membranes far faster than would be feasible by simple diffusion.