Association of urinary macromolecules with calcium oxalate crystals induced in vitro in normal human and rat urine

F. Atmani, F. J. Opalko, S. R. Khan

Research output: Contribution to journalArticle

Abstract

This study was undertaken to identify proteins which are found associated with calcium oxalate crystals induced in vitro in normal human and rat urine. Crystallization was initiated by adding sodium oxalate individually to each urine sample without centrifugation and filtration. Crystals were collected and analyzed by scanning electron microscopy and X-ray diffraction. Crystal matrix proteins (CMPs) were obtained by demineralization of the crystals with ethylenediaminetetra-acetic acid (EDTA) and analyzed by western blotting technique for immunological identification. Crystals produced in human urine were found to be a mixture of calcium oxalate monohydrate (COM) and calcium oxalate dihydrate (COD) while those produced in rat urine were exclusively COD. CMPs extracted from crystals in human urine comprised, in addition to prothrombin-related proteins, osteopontin and albumin. However, CMPs extracted from crystals in rat urine contained only osteopontin and albumin. Prothrombin-related proteins were found only in trace amounts. In a separate experiment, rat urine samples were supplemented with COM before inducing crystallization. Similar results were observed showing that CMP contained osteopontin, albumin and trace amounts of prothrombin-related proteins. We conclude that several urinary macromolecules including not only prothrombin-related proteins, but also osteopontin and albumin, become associated with CaOx crystals. The incorporation of these proteins in growing stones is not only due to the presence of γ-carboxyglutamic acid as it was suggested for prothrombin-related proteins, but may be due to other factors such as urinary chemistry, presence of glutamic and aspartic acid residues, and calcium-binding sites.

Original languageEnglish (US)
Pages (from-to)45-50
Number of pages6
JournalUrological Research
Volume24
Issue number1
DOIs
StatePublished - 1996
Externally publishedYes

Keywords

  • Albumin
  • Calcium oxalate
  • Nephrolithiasis
  • Osteopontin
  • Prothrombin
  • Urine

ASJC Scopus subject areas

  • Urology

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