SLUSHER, L.; MISQUITH, G.; GAVERWITZ, L.; CASOTTI, G.; West Chester University: Expression and localization of aquaporin homologs in the avian kidney

Aquaporins (AQP�s) are membrane integral proteins involved in the passage of water across cell membranes in animals, plants and bacteria. We examined the kidneys of house sparrows for the presence of nine different aquaporin homologs (AQP1 – 9). The kidneys of 8 house sparrows were fixed (4 in low and 4 in high osmolality fixative), and processed for immunohistochemistry. Primary antibodies specific to aquaporins 1�9 were purchased commercially and used in a standard immunohistochemistry procedure. Homologs to aquaporins 1, 7, 8 and 9 were present in the kidneys. Within the medulla, homologs to AQPs 1 and 9 seem to be concentrated in the thick ascending limbs of Henle, where as the distribution of the homologue to AQP 7 seemed restricted to the collecting ducts. Within the medulla, the collecting ducts, and thin and thick limbs of Henle all immunostained for the presence of the homologue to AQP 8. A homologue to mammalian AQP 9 stained the podocytes of the glomeruli and the distal tubules in house sparrows. No evidence was found of homologs to AQP�s 2, 3, 4 or 6 which have been found in various species of mammals. These data suggest that the expression pattern of AQP�s may differ between birds and mammals. We are currently working to isolate and clone the avian AQP�s. These data may help to explain why the avian kidney has a limited urine concentrating ability compared to that of the mammalian kidney. Funded by FDC 2112-004.