A competitive binding assay for measurement of heparan sulfate in tissue digests

Glycosaminoglycans complex with constituents of normal human serum, a finding that was exploited to develop a competitive binding assay for these substances. Heparan sulfate was isolated from renal cortex and radiolabeled with tritiated borohydride. The elution pattern of the radiolabeled material on Sephadex G-25, Bio-Gel P-30, and AG- 1X8 resin was identical to that of unlabeled heparan sulfate. The tritiated heparan sulfate formed radiolabeled precipitates when incubated with serum and zinc acetate. Binding was dose dependent and saturable. Heparin, heparan sulfate, and the chondroitin sulfates, but not hyaluronate or keratan sulfate, competed with the radiolabeled heparan sulfate for binding in a dose-dependent manner. The assay is specific for heparin polysaccharides in chondroitinase ABC-treated samples and is sensitive to microgram quantities.