Chemical and histochemical studies of glomerular sialoprotein in nephrotoxic nephritis in rats

Glomerular sialoprotein (GSP) in nephrotoxic nephritis (NTN) rats was studied by chemical and histochemical methods at 1 to 2 hours, 48 hours, 10 days and 16 days after the induction of the disease by intravenous injection of rabbit antiserum to whole rat glomeruli. Histochemically, GSP was demonstrated by the CI and AB 8 GX stains. After the specimen was taken for histologic studies, the glomeruli from the kidneys of each rat were isolated by differential seiving and centrifugation. Quantitative determination of the glomerular sialic acid content from each rat was done using a combination of the chromatographic method of Svennerholm and the thiobarbituric acid assay of Warren. In normal rats the GSP is seen on the epithelial aspect of the glomerular basement membrane (GBM). Within 1 to 2 hours after induction of NTN, disruptuin of the normal membranous distribution of GSP and its dispersion into the mesangial space or the epithelial cytoplasm was noted. Reduction in the amount of staining was also observed after 48 hours. These changes increased in severity as the histologic lesions progressed. A quantitative decrease in glomerular sialic acid became apparent 10 days after the onset of NTN and was still observed at 16 days. Since GSP is situated at the filtration barrier site and is considered a major component of the glomerular antigenic structure, its changes in NTN suggest that it may play an important role in the pathogenesis of this disease and in the alteration of GBM permeability.