title: Characterization of Tamm-Horsfall protein in a rat nephrolithiasis model.
abstract: OBJECTIVE
  The role of Tamm-Horsfall protein in calcium oxalate stone formation is controversial. It is unclear whether Tamm-Horsfall protein has a role in crystallization. If it does, does it act as an inhibitor or promoter of crystallization? To elucidate the nature of its involvement we characterized Tamm-Horsfall protein in a rat model of calcium oxalate nephrolithiasis by in vivo and in vitro techniques.
  
  
  METHODS
  Calcium oxalate nephrolithiasis was induced in male Sprague-Dawley rats. The amino acid and carbohydrate composition of Tamm-Horsfall protein from normal rats and those with nephrolithiasis was determined. The Tamm-Horsfall protein gene and protein expression in the kidneys were examined by in situ hybridization and immunohistochemistry. Furthermore, the interaction of Tamm-Horsfall protein and calcium oxalate crystals was assessed by an in vitro crystal aggregation assay.
  
  
  RESULTS
  Tamm-Horsfall protein from rats with nephrolithiasis was biochemically similar to that from normal rats. Although Tamm-Horsfall protein was associated with crystal deposits in the renal papillae of rats with nephrolithiasis, Tamm-Horsfall protein messenger RNA expression in the kidneys remained unchanged. In each group Tamm-Horsfall protein inhibited calcium oxalate crystal aggregation by 47%, indicating no change in functional capabilities.
  
  
  CONCLUSIONS
  The results of this study indicate that urinary excretion, and the biochemical nature and functional capabilities of Tamm-Horsfall protein remain unchanged during experimental calcium oxalate nephrolithiasis. Although staining for Tamm-Horsfall protein was evident in the papillae of rats with nephrolithiasis, the site of Tamm-Horsfall protein synthesis remained cells of the thick ascending limbs of the loop of Henle.
authors.affiliation: Department of Pathology, University of Florida, Gainesville, USA.
authors.forename: J A
authors.initials: JA
authors.lastname: Gokhale
authors.forename: P A
authors.initials: PA
authors.lastname: Glenton
authors.forename: S R
authors.initials: SR
authors.lastname: Khan
mesh_terms: D000818:Animals; D003460:Crystallization; D007669:Kidney Calculi / Q000209:etiology*; D008297:Male; D009088:Mucoproteins / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D017207:Rats, Sprague-Dawley; D058949:Uromodulin
chemical_list: D009088:Mucoproteins; D012333:RNA, Messenger; C548614:Umod protein, rat; D058949:Uromodulin