Growth of calcium oxalate crystals. II. Inhibition by natural urinary crystal growth inhibitors.

A method is described for quantitatively determining the inhibitory activity of pure components, isolates, or mixtures of components (such as urine) on the growth of calcium oxalate crystals. Results with known calcium phosphate crystal growth inhibitors--magnesium, citrate, and pyrophosphate--suggest that these components contribute little to the ability to normal urine to inhibit the growth of calcium oxalate crystals. As yet unidentified urinary components seem to be responsible for most of this activity. The urinary crystal growth inhibitors appear to function by adsorbing on the surface of the growing crystals, thereby preventing the further incorporation of lattice ions. The fit of experimental data to the Langmuir absorption isotherm supports this conclusion.