CASOTTI, G.; BRAUN, E.J.: Protein localization in avian urine spheres

Uricotelic vertebrates excrete uric acid in the form of spheres (1-15 �m in size) in their urine. In addition to uric acid, the spheres contain protein and inorganic ions. In an attempt to determine how they are formed within the nephron, we processed spheres for scanning electron microscopy to examine their internal structure. We also processed spheres for immunohistochemistry and examined them for the presence and distribution of protein using FITC (Molecular Probes). Internally, the spheres consist of concentric layers. Immunohistochemical analyses indicate that these rings are made up, in part, of protein. In on going investigations we hope to examine the spheres for the location of inorganic ions and uric acid. We hypothesize that the spheres are formed within the nephron by concentric layers of protein, binding inorganic ions and urate.