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Query: UMLS:C0451641 (
urolithiasis
)
3,973
document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)
This is a comparative study of the effects of phytate and pyrophosphate and other polyphosphates on the crystallization of hydroxyapatite and brushite, the most frequent calcium phosphates involved in calcium oxalate
urolithiasis
. Brushite and hydroxyapatite crystal formation was studied in synthetic urine, through kinetic-turbidimetric measurements that allowed evaluation of the inhibitory effects on crystallization of insoluble salts. The effectiveness in preventing brushite crystallization decreases in the sequence phytate > polyphosphate > EDTPO > etidronate > pyrophosphate > triphosphate > medronate; whereas the order of effectiveness in preventing hydroxyapatite crystallization was EDTPO > etidronate = pyrophosphate > triphosphate > medronate > polyphosphate > phytate.
Phytate
, a natural inhibitor in urine, most effectively blocked brushite precipitation (1.21x10(-5) M prevented crystallization during time periods of at least 1 h), and pyrophosphate was the natural inhibitor that most effectively blocked hydroxyapatite precipitation (2.87x10(-6) M prevented crystallization during time periods of at least 1 h). This demonstrates that low excretion of these substances would pose a risk of renal lithiasis.
...
PMID:Effects of phytate and pyrophosphate on brushite and hydroxyapatite crystallization. Comparison with the action of other polyphosphates. 1085 Jun 38
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
2+
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
2+
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
-11
, 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.
Urolithiasis
2019 Dec
PMID:Potential thermodynamic and kinetic roles of phytate as an inhibitor of kidney stone formation: theoretical modelling and crystallization experiments. 3076 40
