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Reduced crystallization inhibition by urine from women with nephrolithiasis
John R Asplin1, Joan H Parks, Yashushi Nakagawa
1Renal Section, University of Chicago, and Litholink Corporation, Chicago, Illinois 60637, USA.
Background:
Human urine is known to inhibit growth, aggregation, nucleation, and cell adhesion of calcium oxalate monohydrate (COM) crystals, the main solid phase of human kidney stones. This study tested the hypothesis that low levels of inhibition are present in women with calcium oxalate stones and, therefore, could promote stone production.
Methods:
In 17 stone-forming women and 17 normal women matched in age within five years, inhibition by dialyzed urine proteins of COM growth and aggregation was examined, as well as whole urine upper limits of metastability (ULM) for COM and calcium phosphate (CaP) in relation to the corresponding supersaturation (SS).
Results:
Compared to normals, patient urine showed a reduced ULM in relation to SS. In contrast to men, there was no difference in growth inhibition.
Conclusions:
Reduced CaP and CaOx ULM values in relation to SS are a characteristic of female stone formers. This defect could promote stones by facilitating crystal nucleation. Abnormal inhibition may well be a very important cause of human nephrolithiasis.