Status of glomerular proteoglycans in aminonucleoside nephrosis

Abstract

Status of glomerular proteoglycans (PGs) in puromycin aminonucleoside nephrosis was investigated. Rats were made nephrotic and sacrificed 0, 7, 14, and 21 days later. Maximal proteinuric response was observed between 7 and 14 days. Prior to sacrifice, they received injections of conjugated or unconjugated anti-heparan-sulfate-proteoglycan antibody, directed against its core protein (Mr = 18,000). Their kidneys were processed for direct and indirect immunofluorescence, immunoperoxidase, tannic-acid staining, and tissue autoradiography (ARG). By tannic-acid staining, antibody binding sites identical to the anionic sites described previously were discovered. No qualitative differences were observed by these immunohistochemical techniques. Quantitative tissue ARG did not reveal any statistical differences in the binding of antibody between the control and nephrotic groups. For de novo biosynthetic studies, rats were sacrificed on day 10. Their kidneys were utilized for labeling of basement membrane PGs by employing [35S]-sulfate as the precursor product. Tissue ARG, as well as biochemical studies, were performed on the radiolabeled glomeruli. PGs were extracted with 4 M GuCl and characterized by Sepharose CL-6B and DEAE-Sephacel chromatography. There was an overall increase in the total incorporated radioactivities in the glomerular and media fractions. No differences were observed in the macromolecular size characteristics of intact PGs and glycosaminoglycan chains of either glomerular or media fractions. However, an increase in the charge-density characteristics was observed in PGs of the nephrotic group. By tissue ARG, an increase in the grain densities over the basement membrane and mesangial matrices of the glomerulus was noted. These data indicate that the intact PGs, their chains and core protein do not undergo significant biochemical alterations; however, de novo synthesized PGs have higher charge-density characteristics which may be related to a higher degree of sulfation that occurs during the course of aminonucleoside nephrosis.