title: In vivo effects of nitrogen dioxide and ozone on xenobiotic metabolizing systems of rat lungs.
abstract: Male Jcl:Wistar rats were exposed continuously to either ozone (O3) or nitrogen dioxide (NO2) for 7 and 14 days to examine the effects of these gases on the xenobiotic metabolizing systems of lung microsomes. Exposure to 0.2 and 0.4 ppm O3 increased NADPH-cytochrome P-450 reductase activity and cytochrome P-450 as well as microsomal protein by the 14th day, whereas NADH-cytochrome b5 reductase was not affected. The most marked increase was observed in cytochrome P-450. In parallel to this increment, the activities of benzo(a)pyrene hydroxylase and 7-ethoxycoumarin O-deethylase of exposed animals increased significantly on the 7th and 14th days of exposure to 0.2 and 0.4 ppm 03. In contrast, exposure to 1.2 and 4 ppm NO2 decreased cytochrome P-450 on the 7th day. Moreover, the 7-ethoxycoumarin O-deethylase activity in exposed animals decreased to 61% (P less than 0.05) and 74% (P less than 0.001) of control on the 7th and 14th days of exposure to 4 ppm NO2, respectively. This decrease occurred in a dose-dependent manner with exposure to 0.4-4.0 ppm NO2, whilst benzo(a)pyrene hydroxylase activity was not affected. These results show that O3 at low doses induces xenobiotic metabolizing activities in the lung, whereas NO2 reduces this.
mesh_terms: D015660:7-Alkoxycoumarin O-Dealkylase; D000818:Animals; D001273:Atmosphere Exposure Chambers; D001579:Benzopyrene Hydroxylase / Q000378:metabolism; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism; D004790:Enzyme Induction / Q000187:drug effects; D008168:Lung / Q000187:drug effects* / Q000201:enzymology; D008297:Male; D008861:Microsomes / Q000187:drug effects / Q000201:enzymology; D009251:NADPH-Ferrihemoprotein Reductase / Q000378:metabolism; D009585:Nitrogen Dioxide / Q000633:toxicity*; D010105:Oxygenases / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000378:metabolism*; D010126:Ozone / Q000633:toxicity*; D051381:Rats; D011919:Rats, Inbred Strains
chemical_list: D010126:Ozone; D003577:Cytochrome P-450 Enzyme System; D010105:Oxygenases; D015660:7-Alkoxycoumarin O-Dealkylase; D001579:Benzopyrene Hydroxylase; D009251:NADPH-Ferrihemoprotein Reductase; D009585:Nitrogen Dioxide