BURNS, A. C.; ARCHER, J.; SLUSHER, C.; SLUSHER, L.; CASOTTI, G.: Expression and Localization of Aquaporins in the Lower Intestinal Tract of Birds

Aquaporins (AQP�s) are membrane integral proteins involved in the passage of water across cell membranes in animals, plants and bacteria. We examined the lower intestinal tract of house sparrows for the presence of nine different aquaporins (AQP1-9). The intestines of six house sparrows were divided into four regions: cecae, proximal rectum, distal rectum and coprodeum, and processed for immunocytochemistry. Primary antibodies specific to aquaporins 1�9 were purchased commercially and used in a standard immunocytochemistry procedure. Aquaporins 1, 6, 7, 8 and 9 (mostly aquaglyceroporins) were present in the lower intestinal tract. Within the cecae, all five AQP�s were present in the glandular mucosa, but absent from the epithelium. In the proximal rectum, all five AQP�s were present in the villus epithelium predominently toward the basolateral cell membrane, and in the lamina propria. In the distal rectum, only AQP�s 1 and 9 were present within the villus epithelium and in the lamina propria. In the coprodeum, only AQP�s 1, 6 and 9 were present, and only in the lamina propria. No evidence was found of AQP�s 2, 3, 4 or 5. These data for house sparrows support previous physiological studies indicating a high water transport capacity across cells within the lower intestine of birds. In mammals, AQP�s 1, 3, 4 and 8 have been found in the lower intestinal tract. Thus, our data for the house sparrow differs slightly from those for mammals. It appears that only AQP�s 1 and 8 are shared by animals in both classes. Funded by FDC 2112-004.