brain, mammalian lens, bacteria, and plants. Since the function was unknown, Agre consulted John C. Parker, his former hematology professor at the University of North Carolina, who suggested that the protein may be the long-sought water channel responsible for rapid movements of water across the membranes of red cells and certain other cell types. Teaming up with William Guggino at the Department of Physiology at Johns Hopkins, Agre's postdoctoral fellow Gregory Preston confirmed water channel function by expressing the cRNA in Xenopus laevis oocytes (frog eggs) that then became osmotically active and exploded in fresh water. The 28 kDa protein is now known as aquaporin-1 (abbreviated AQP1), the archetypal member of a large family of water channel proteins. Aquaporins are "the plumbing system for cells," said Agre. Every cell is primarily water. "But the water doesn't just sit in the cell, it moves through it in a very organized way. The process occurs rapidly in tissues that have these aquaporins or water channels." For 100 years, scientists assumed that water leaked through the cell membrane, and some water does. "But the very rapid movement of water through some cells was not explained by this theory," said Agre. Agre's team and others identified paralogs in different tissues, and twelve aquaporins exist in humans. Permeated by water, aquaporins are required for generation of cerebrospinal fluid, aqueous humour, tears, sweat, saliva, humidification of airways, and renal concentration. Defects include cerebral edema, dry eye, anhydrosis, dehydration and water retention. Permeated by water plus glycerol, aquaglyceroporins confer glycerol uptake to the basal level of skin, glycerol release from fat during fasting, and glycerol uptake by liver where it is converted to glucose. Aquaporins and aquaglyceroporins exist in all life forms including invertebrates, plants, microbes, archaea, and parasites including the plasmodia that cause malaria. 2003 Nobel Prize in Chemistry In October 2003, it was announced that the Nobel Prize in Chemistry would go to two medical doctors, Peter Agre and Roderick MacKinnon, "for discoveries concerning channels in cell membranes." Credited for discovery of the aquaporin water channels, Agre was in bed at 5:30 am when the call came from Stockholm. Upon learning the news later, his mother responded, "That's very nice but don't let it go to his head." MacKinnon, credited with solving the structure and selectivity of potassium channels, was traveling back from a weekend fishing trip and only learned the news from colleagues. Malaria