Glycosaminoglycans in Crystal-Surface Binding Substances and Their Role in Calcium Oxalate Crystal Growth

Objective To clarify the role of glycosaminoglycans (GAGs) in crystal-surface binding substances (CSBS) on the growth of calcium oxalate crystals in urine. Materials and methods Urine samples (24 h) were collected from healthy men (aged 25-42 years) and CSBS were obtained from the pooled urine samples. The CSBS were digested with heparitinase or proteinase and the inhibition of crystal growth assessed before and after enzyme digestion. Anion-exchange chromatography and high-performance liquid chromatography (HPLC) were used to determine the types of GAGs contained in the CSBS. Results The inhibitory activity of CSBS on crystal growth decreased with concentration when digested with heparitinase or proteinase. HPLC showed that CSBS contained a small amount of dermatan sulphate and abundant heparan sulphate, both of which inhibited crystal growth. Conclusion Both heparan sulphate and dermatan sulphate may inhibit calcium oxalate crystallization, the former being the predominant GAG in CSBS.