1Department of Chemistry, University of Cape Town, Rondebosch, Private Bag, Cape Town, 7701, South Africa.
Urolithiasis. 2019 Dec;47(6):493-502. doi: 10.1007/s00240-019-01117-1. Epub 2019 Feb 14.
Kidney stone formation is governed by thermodynamic (supersaturation) and kinetic (crystal nucleation, growth, aggregation) mechanisms. We adopted a dual theoretical and experimental approach to investigate the potential role of urinary phytate in this regard. Thermodynamic constants for eight protonated phytate species and seven calcium-phytate complexes were determined by potentiometry and incorporated into the speciation program JESS. Urine was collected from 16 heathy males and their urine compositions were used as input for JESS. Phytate concentration was varied during modelling. No statistically significant decreases in Ca concentrations or in supersaturation values were predicted by JESS. Crystallization experiments were then performed in pooled urine. Endogenous phytate concentration was determined using a metal-dye assay. The pool was dosed with various concentrations of phytate to achieve final concentrations equivalent to those used for modelling. Experiments showed that phytate had no effects on Ca concentrations (as predicted by our theoretical modelling), metastable limits or crystal nucleation and growth kinetics. However, crystal aggregation kinetics was inhibited. We speculate that HPhy, small amounts of which were revealed by modelling, may bind to crystal surfaces and inhibit aggregation. We conclude that phytate exerts a kinetic, but not a thermodynamic inhibitory effect on crystallization in urine.
肾结石的形成受热力学（过饱和度）和动力学（晶体成核、生长、聚集）机制的控制。我们采用了理论和实验相结合的方法来研究尿植酸在这方面的潜在作用。通过电位滴定法确定了八种质子化植酸物种和七种钙-植酸络合物的热力学常数，并将其纳入了物种形成程序 JESS 中。从 16 名健康男性中收集尿液，并将其尿液成分用作 JESS 的输入。在建模过程中改变了植酸浓度。JESS 没有预测到 Ca 浓度或过饱和度值有统计学意义的降低。然后在混合尿液中进行了结晶实验。使用金属染料测定法测定内源性植酸浓度。向池内加入不同浓度的植酸，以达到与建模中使用的浓度相当的终浓度。实验表明，植酸对 Ca 浓度（如我们的理论建模所预测）、亚稳限或晶体成核和生长动力学没有影响。然而，晶体聚集动力学受到抑制。我们推测，建模中揭示的少量 HPhy 可能与晶体表面结合并抑制聚集。我们得出结论，植酸对尿液中的结晶具有动力学而非热力学抑制作用。
