CRYSTALLIZATION OF URINARY CALCIUM-OXALATE AT STANDARDIZED OSMOLALITYAND PH IN THE FROZEN STATE

The potential of whole urine of stone-farmers and normal controls to p recipitate crystals of calcium oxalate dihydrate from ions endogenous in urine was investigated by the method of rapid evaporation to 1250 m Osm/kg and subsequent freezing. Over 90% incidence in crystallization was achieved in the two groups, When the population density and size o f these crystals were compared, it was found that 50% of urine samples from stone formers (30-50 years of age) were rich in crystal-nucleati ng and growth-inhibiting factors and the other 50% were not different from normal controls. These effects were observed when polyanionic mac romolecules recovered from pooled urine samples of stone-formers or no rmal controls were dissolved in urine ultrafiltrate and similarly test ed. That the urinary polyanions were the active modifiers in the test system was further corroborated by the reversal of crystallization act ivity of urine samples and the urinary polyanions after they had been through an acidification-reneutralization procedure. The urinary polya nionic macromolecules were found, after enzymatic and/or chemical trea tment, to contain chondroitin sulphates, dermatan sulphates, heparan s ulphates and glycoproteins.