Isolation and characterization of proteoheparan sulfate synthesized in vitro by rat glomeruli

Glomeruli isolated from rat kidney were incubated with [14C]glucosamine and [35S]sulfate. Linear incorporation of [14C]glucosamine into total glycosaminoglycans was observed during incubation up to 24 h. More than 95% of the 35S-labeled sulfated glycoconjugates were extracted from the tissue with 4 M guanidine HCl, 50 mM sodium acetate, pH 6.0, and 0.5% Triton X-100, and separated clearly on DEAE-Sephacel into three major fractions, i.e. sulfated glycoprotein (11% of the total radioactivity), proteoheparan sulfate (33%), and proteochondroitin sulfate (38%) fractions. The molecular weight of the 35S-labeled proteoheparan sulfate thus isolated was estimated to be about 185,000, whereas that released into the medium was estimated to be about 87,000. When the 35S-labeled heparan sulfate isolated on Sephadex G-75 after mild alkaline borohydride treatment was digested with a combination of heparitinase and heparinase, approximately 70% of the radioactivity was converted to 2-acetamido-2-deoxy-4-O-(alpha-D-gluco-4-enepyranosyluronic acid)-6-O-sulfo-D- glucose.