The epithelial glomerular polyanion (GPA) designates an array of sialic acid-containing sites along the surface of the glomerular epithelium which react with cationic dyes or probes. In this work, sequential rat glomerular isolation, ultrasonic disruption, trypsin digestion, ion-exchange chromatography, and preparative polyacrylamide gel electrophoresis have been used to isolate anionic sialoglycoproteins from the glomerular epithelium. Because colloidal iron (CI) reactivity has been used to define the GPA histologically, we used a modification of the CI reaction to monitor and direct the isolation procedure. Three major fractions have been recognized and isolated in homogeneity. Antibodies to two of the fractions have been raised by immunization in rabbits. Indirect immunofluorescent and peroxidase-antibody techniques have localized both antigens to the glomerular visceral epithelium of normal rat kidney. This identification and definition of components of the GPA is valuable in delineating a role for GPA in glomerular function.
Bibliographical noteFunding Information:
abstract form. This work was aided by a grant from the National Institutes of Health (A1l0704). Dr. Nevins carried out this study during the tenure of a Postdoctoral Fellowship from the National institutes of Health (SF32 AM05720) and the Tern L. Kasch Fellowship Award. We acknowledge the assistance of Dr. R. Vernier for interpreting the electron micrographs, Ms. S. Sisson for performing immunoelectron microscopy, and Dr. M. Houser for providing the radiolabeled GBM and assisting in the enzyme assay. Ms. J. Aplin prepared the manuscript, and Mr. M. Hoff prepared the illustrations.