title: Structural and functional modification of THP on nitration: comparison with stone formers THP.
abstract: OBJECTIVE
  The crucial steps involved in the lithogenic process are governed by the macromolecular components of urine, of which proteins play a major role. Structurally abnormal proteins have been reported to be present in the urine of stone formers. Free radical injury has come a long way in explaining some of the pathophysiological events of renal lithiasis. Thus, our present work was designed to study the impact of the potent oxidant peroxynitrite on the biochemical components of the urinary Tamm-Horsfall glycoprotein (THP).
  
  
  METHODS
  Nitration on THP was carried out using peroxynitrite (ONOO(-)). After nitration, biochemical components like thiols, S-nitrosothiol, hexose, hexosamine and sialic acid were determined and these factors were compared with those of stone formers and normal THP. Crystallization behavior of control, nitrated NS-THP and stone formers THP was studied.
  
  
  RESULTS
  There was a significant decrease in thiol, hexose, hexosamine and sialic acid contents in stone formers and nitrated NS-THP, when compared to that of the control THP. In contrast to this, S-nitrosothiol content was significantly increased in stone formers and nitrated NS-THP (p < 0.001) when compared with the control THP. NO(x) metabolites were significantly elevated in stone formers THP when compared with that of control THP. When subjected to CaOx crystallization, stone formers THP and nitrated NS-THP promoted both CaOx nucleation and aggregation, while normal THP was found to be an inhibitor of the above processes.
  
  
  CONCLUSIONS
  From our results we conclude that nitration of THP could represent one of the prime events in modifying kinetic behavior of THP, thus converting THP into a heterogeneous nucleator of renal calculi formation.
authors.affiliation: Department of Medical Biochemistry, University of Madras, Dr. ALM PGIBMS, Taramani, Chennai, India.
authors.forename: Viswanathan
authors.initials: V
authors.lastname: Pragasam
authors.forename: Periandavan
authors.initials: P
authors.lastname: Kalaiselvi
authors.forename: Balasubramanian
authors.initials: B
authors.lastname: Subashini
authors.forename: Kamalanathan
authors.initials: K
authors.lastname: Sumitra
authors.forename: Palaninathan
authors.initials: P
authors.lastname: Varalakshmi
mesh_terms: D003460:Crystallization; D006801:Humans; D007700:Kinetics; D046911:Macromolecular Substances / Q000737:chemistry / Q000652:urine; D009088:Mucoproteins / Q000097:blood* / Q000652:urine*; D009566:Nitrates / Q000737:chemistry* / Q000652:urine*; D014545:Urinary Calculi / Q000737:chemistry* / Q000652:urine*; D058949:Uromodulin
chemical_list: D046911:Macromolecular Substances; D009088:Mucoproteins; D009566:Nitrates; C548612:UMOD protein, human; D058949:Uromodulin