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A selective enhancement of xenobiotic metabolizing systems of rat lungs by prolonged exposure to ozone

Environmental Research, ISSN: 0013-9351, Vol: 42, Issue: 2, Page: 425-434
1987
  • 17
    Citations
  • 0
    Usage
  • 3
    Captures
  • 0
    Mentions
  • 0
    Social Media
Metric Options:   Counts1 Year3 Year

Metrics Details

  • Citations
    17
    • Citation Indexes
      16
    • Policy Citations
      1
      • Policy Citation
        1
  • Captures
    3

Article Description

Male Wistar rats were exposed to 0.2 and 0.4 ppm O 3 for 4, 8, and 12 weeks and to 0.1 and 0.2 ppm O 3 for 4 weeks to examine the effects of prolonged exposure to O 3 on the xenobiotic metabolizing systems in the lung. Exposures to 0.2 and 0.4 ppm O 3 caused a significant increase in the NADPH-cytochrome P-450 reductase activity and cytochrome P-450 content in a dose-dependent manner during 4–12 weeks, whereas NADH-cytochrome b 5 reductase was not altered. After 12 weeks of exposure to 0.4 ppm O 3, NADPH-cytochrome P-450 reductase and cytochrome P-450 reached a maximum showing 138 ( P < 0.001) and 221% ( P < 0.001) those of the control levels, respectively. At 0.1 ppm O 3, the cytochrome P-450 content still increased significantly to 152% that of the control on the fourth week. In parallel to the increment of cytochrome P-450 benzo( a )pyrene hydroxylase and 7-ethoxycoumarin O -deethylase increased significantly during 4–12 weeks of exposures to 0.2 and 0.4 ppm O 3. After a 4-week exposure to 0.1 and 0.2 ppm O 3, benzphetamine N -demethylase increased to the largest degree among the enzymes metabolizing four kinds of xenobiotics examined. 7-Ethoxycoumarin O -deethylase also increased significantly but of smaller magnitude, whereas coumarin hydroxylase was not affected. These results show that prolonged exposures to 0.1–0.4 ppm O 3 persistently enhance pulmonary cytochrome P-450 systems. It is also suggested that some isozyme(s) of pulmonary cytochrome P-450, especially that catalyzing benzphetamine N-demethylation, are preferentially increased by exposure to low levels of O 3.

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