The dual effect of urinary macromolecules on the crystallization of calcium oxalate endogenous in urine.

The nucleation-promoting and growth-inhibiting activities of urinary macromolecules on the crystallization of calcium oxalate endogenous in urine of stoneformers and normal controls were studied by freezing the ultrafiltrate and retenate fractions of concentrated whole urine (pH 5.3, 1,250 mosmol/kg). Among the normal controls, macromolecules nominally of 10-20 kDa showed nucleation-promoting and growth-inhibiting activities; the 5-10 kDa population was incapable of such effects but did cooperate with molecules greater than 10 kDa in enhancing the effect. In the case of stone-formers, molecules in the nominal ranges of 5-10 kDa and 10-20 kDa when considered separately were not active in the aspects studied but collectively could cooperate to produce pronounced effects. Application of the test to urine ultrafiltrate reconstituted with polyanionic macromolecules recovered from urine indicated that molecules from stoneformers were more powerful than those from normal controls in bringing about promotion of nucleation and inhibition of growth of crystals from urinary calcium oxalate.