Isolation, characterization and immunological determination of basement membrane-associated heparan sulfate proteoglycan

Basement membrane-associated heparan sulfate proteoglycan (HSPG) was extracted from isolated porcine glomerular basement membranes and purified by ion-exchange chromatography. The proteogycan was characterized by specific enzymatic digestions, by amino-acid analysis, by SDS-polyacrylamide gel electrophoresis and by density gradient centrifugation. Polyclonal antibodies were raised against the purified HSPG in rabbits. Antibodies were characterized by enzyme immunoassays, immunoprecipitation and immunohistological methods. They were shown to recognize specifically the core protein of HSPG from porcine, human and rat glomerular basement membrane but did not recognize HSPG from guinea pig or rabbit kidney. The affinity-purified antibodies did not cross-react with other basement membrane proteins like laminin, fibronectin or collagen type IV nor with chondroitin sulfate-rich or keratan sulfate-rich proteoglycans from human or bovine tissue. Using these antibodies an enzyme immunoassay was developed for determination of HSPG in the range of 1-100 ng/ml. Studies with cultured porcine endothelial cells showed that subendothelial basement membrane-associated HSPG may be determined with the enzyme immunoassay.