title: Uric acid as inducer of calcium oxalate crystal development.
abstract: OBJECTIVE
  This paper deals with the mechanism by which uric acid affects calcium oxalate crystallization and the role of crystallization inhibitors in this process.
  
  
  METHODS
  Pure uric acid crystals and fragments of uric acid renal calculi were used to induce calcium oxalate crystal formation and development. These studies were performed in flow systems, using synthetic urine and similar conditions to those found in real renal situations. The type and size of the developed crystals were evaluated by scanning electron microscopy and the amount of calcium oxalate crystallized was quantitated by means of inductively coupled plasma atomic emission spectroscopy.
  
  
  RESULTS
  The presence of uric acid crystals in a flow system provoked calcium oxalate monohydrate (COM) crystallization at a rate of 3.3 microg/h/mg uric acid. When uric acid renal calculi fragments were used, the amount of COM crystallized varied between 0.048 and 0.161 microg/h/mg of renal calculi depending on the porosity of the calculus. At particular concentrations (3.03 microM phytate, 28.75 microM pyrophosphate, 40 mg/l chondroitin sulphate) the crystallization inhibitors assayed produced a maximum decrease of approximately 50% in the amount of COM crystallized on uric acid crystals. Mucin (a glycoprotein) caused only slight effects.
  
  
  CONCLUSIONS
  Uric acid crystals can clearly induce the development of COM crystals on them through a heterogeneous nucleation process and some crystallization inhibitors can notably delay such a process.
authors: Laboratory of Renal Lithiasis Research, University Institute of Health Sciences Research (IUNICS), University of Balearic Islands, Palma de Mallorca, Spain. fgrases@uib.es
authors: Félix
authors: F
authors: Grases
authors: Pilar
authors: P
authors: Sanchis
authors: Bernat
authors: B
authors: Isern
authors: Joan
authors: J
authors: Perelló
authors: Antònia
authors: A
authors: Costa-Bauzá
mesh_terms: D002129:Calcium Oxalate / Q000652:urine*; D003460:Crystallization; D006801:Humans; D010833:Phytic Acid / Q000494:pharmacology; D014527:Uric Acid / Q000494:pharmacology*
chemical_list: D002129:Calcium Oxalate; D014527:Uric Acid; D010833:Phytic Acid