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.