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Trichloroethylene-induced mouse lung tumors: studies of the mode of action and comparisons between species.

Abstract
CD-1 mice exposed to 450 ppm trichloroethylene, 6 hr/day, 5 days/week, for 2 weeks showed a marked vacuolation of lung Clara cells after the first exposure of each week and a marked increase in cell division after the last exposure of each week. The damage seen in mouse lung Clara cells is caused by an accumulation of chloral resulting from high rates of metabolism of trichloroethylene but poor clearance of chloral to trichloroethanol and its glucuronide. The activity and distribution of the key metabolizing enzymes in this pathway have been compared in mouse, rat, and human lung. While mouse lung microsomal fractions were able to metabolize trichloroethylene to chloral at significant rates, the rate in rat lung was 23-fold lower and a rate could not be detected in human lung microsomes at all. Immunolocalization of cytochrome P450IIE1 in lung sections revealed high concentrations in mouse lung Clara cells with lesser amounts in type II cells. Lower levels of enzyme could be detected in Clara cells of rat lung, but not at all in human lung sections. Western blots of lung tissues from the three species and of mouse lung Clara cells were entirely consistent with these observations. Consequently, it is highly unlikely that humans exposed to trichloroethylene are at risk from the lung damage/cell proliferation mechanism that is believed to lead to the development of tumors in the mouse lung.
AuthorsT Green, G W Mainwaring, J R Foster
JournalFundamental and applied toxicology : official journal of the Society of Toxicology (Fundam Appl Toxicol) Vol. 37 Issue 2 Pg. 125-30 (Jun 1997) ISSN: 0272-0590 [Print] United States
PMID9242585 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)
Chemical References
  • Glucuronates
  • Solvents
  • Trichloroethylene
  • Chloral Hydrate
  • Ethylene Chlorohydrin
  • 2,2,2-trichloroethanol
  • Cytochrome P-450 CYP2E1
  • trichloroacetaldehyde
Topics
  • Administration, Inhalation
  • Animals
  • Blotting, Western
  • Cell Division
  • Chloral Hydrate (analogs & derivatives, metabolism, toxicity)
  • Cytochrome P-450 CYP2E1 (metabolism)
  • Ethylene Chlorohydrin (analogs & derivatives, metabolism)
  • Female
  • Glucuronates (metabolism)
  • Humans
  • Immunoenzyme Techniques
  • In Vitro Techniques
  • Lung (drug effects, enzymology, pathology)
  • Lung Neoplasms (chemically induced, enzymology, pathology)
  • Male
  • Mice
  • Microsomes (drug effects, enzymology)
  • Microsomes, Liver (drug effects, enzymology)
  • Rats
  • Rats, Wistar
  • Solvents (metabolism, toxicity)
  • Species Specificity
  • Trichloroethylene (metabolism, toxicity)

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