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The Constant Composition (CC) kinetics method has been used for studying the mineralization of calcium oxalate monohydrate (COM) at sustained supersaturations in the presence of pre-bladder urine and macromolecules isolated from normal urine and kidney and bladder stones. The method is especially sensitive for investigating the inhibitory activities of these urinary macromolecular components (UMMC) and matrix macromolecular components (MMMC) with a coefficient of variation in growth rate of approximately 2%. Significant COM mineral inhibition was observed in a wide molecular weight region of urine components. Urine removed directly from the kidney showed appreciable inhibitory activity towards COM crystallization. Normal urinary proteins and the dissolved precipitate resulting from urine centrifugation were fractionated by gel filtration. The resulting solutions were mostly COM mineralization inhibitors. Electrodialysis was utilized to isolate the MMMC (greater than 7000 d) of renal and bladder calculi. While these solutions inhibited COM crystallization, they were also found to be calcium binders as measured by the calcium electrode.

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A constant composition potentiostatic method was used to investigate the crystallization kinetics of calcium oxalate monohydrate with high precision and reproducibility in the presence of whole (centrifuged) and dialyzed urines. The solution supersaturation is maintained constant by the potentiometrically controlled addition of lattice ion solutions. The method allows the calculation of urine inhibitory potentials to be made with a precision (5 per cent) hitherto unattainable, and avoids the complications resulting from large changes in supersaturation implicit in more conventional seeded crystallization experiments. A method of urine storage is described whereby the inhibitory potentials remain constant for up to 7 weeks of sample storage.