title: Binding of titanium dioxide nanoparticles to lactate dehydrogenase.
abstract: OBJECTIVE
  Measurement of released lactate dehydrogenase (LDH) activity, a commonly used marker of lethal cell injury in both in vitro and in vivo screenings, has been used to assess the cytotoxicity of nanoparticles (NPs), chemical compounds, and environmental factors. We have recently demonstrated that titanium dioxide (TiO₂) particles bind to several serum proteins. In the present study we investigated the binding of TiO₂ NPs to LDH.
  
  
  METHODS
  Purified LDH was incubated with TiO₂ NPs at 37°C for 1 h. The particles were then sedimented by centrifugation, and the activity and quantity of LDH in the supernatant and precipitated fraction were analyzed.
  
  
  RESULTS
  Incubation with TiO₂ reduced the LDH activity in the supernatant in a dose-dependent manner, while LDH activity in the precipitated fraction increased in a dose-dependent manner. Moreover, sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis revealed a TiO₂ dose-dependent reduction in the quantity of LDH protein in the supernatant and an increase of LDH in particulate re-suspensions.
  
  
  CONCLUSIONS
  These findings, although based on a purified form of LDH, suggest that TiO₂ NPs bind to LDH, and consequently, TiO₂ NP-induced toxicity could be underestimated by the LDH activity assay.
authors: Department of Occupational Toxicology, Institute of Industrial Ecological Sciences, University of Occupational and Environmental Health, Yahatanishi-ku, Kitakyushu 807-8555, Japan.
authors: Mazen S K
authors: MS
authors: Zaqout
authors: Tomoyuki
authors: T
authors: Sumizawa
authors: Hideki
authors: H
authors: Igisu
authors: Donald
authors: D
authors: Wilson
authors: Toshihiko
authors: T
authors: Myojo
authors: Susumu
authors: S
authors: Ueno
mesh_terms: D000818:Animals; D003720:Densitometry; D004591:Electrophoresis, Polyacrylamide Gel; D007770:L-Lactate Dehydrogenase / Q000378:metabolism*; D053768:Metal Nanoparticles / Q000737:chemistry*; D011817:Rabbits; D014025:Titanium / Q000378:metabolism*; D014874:Water Pollutants, Chemical / Q000378:metabolism*
chemical_list: D014874:Water Pollutants, Chemical; C009495:titanium dioxide; D014025:Titanium; D007770:L-Lactate Dehydrogenase