Analysis of glycosaminoglycans induced in newly formed calcium oxalate crystals using an undiluted urine system

The aim of this study was to examine the effect of sodium pentosan polysulfate (SPP) in an undiluted urine system and to study its relative affinity to calcium oxalate (CaOx) crystals in the presence or absence of heparan sulfate (HS). CaOx crystals were induced with an overload of oxalate above the metastable limit in spun and filtered urine (SF) and ultrafiltered urine (UF). Then, the crystals were dissolved with EDTA (ethylenediaminetetraacetic acid), electrodialysed and lyophilized. The polyanions, HS or SPP were added to the UF prior to the addition of oxalate. Polyanions in crystal matrices were examined by cellulose acetate electrophoresis. Crystal volume and size were suppressed according to the increase of the concentration of SPP when compared with those of the UF. Scanning electron microscopy (SEM) showed marked aggregation of the crystals in the UF and no aggregation in the presence of SPP. HS was the only polyanion found in CaOx crystals formed after overload of oxalate in SF. Crystals formed in UF did not contain any polyanions. When SPP was added to UF, SPP appeared in the crystal matrix in accordance with its concentration. Once HS in physiological concentration was added to the UF containing SPP, HS and SPP obtained from crystals were strongly stained with Alcian blue in electrophoretic study, where SPP is stained stronger than HS. These results suggest that SPP strongly binds to CaOx crystals as well as HS and that HS and SPP competitively bind to the crystal, then, as a result, they are incorporated into the crystals. The fact that SPP suppressed the aggregation of CaOx crystals in undiluted urine showed the possibility that SPP might be one of the useful drugs for preventing CaOx urolithiasis.