title: In vivo effects of nitrogen dioxide on membrane constituents in lung and liver of rats.
abstract: When rats were exposed to 10 ppm NO2 for 7 days, the succinate-cytochrome c reductase activity, the rate-limiting step of mitochondrial succinoxidase, of the liver decreased progressively, reaching 77% (P less than 0.01) of the control level by the fifth day. By contrast, this activity was gradually increased by a 10-day exposure to 4 ppm NO2 and reached 1.14-fold that of the control level at the seventh day. A reduction in the components of electron-transport systems in liver microsomes was found during exposure to NO2 at both concentrations. This reduction was preferential for components of drug-metabolizing systems. The NADPH-cytochrome c reductase activity and the cytochrome P-450 content were decreased to 82% (P less than 0.05) and 76% (P less than 0.05), respectively, at the fifth day of exposure to 10 ppm NO2. Exposure to 4 ppm NO2 also caused a significant decrease in the NADPH-cytochrome c reductase and the cytochrome P-450 content, which were lowered to 84% (P less than 0.05) of the control level at the fourth and seventh days, respectively. Reduction in these components appears to occur even at the concentration of 0.4 ppm at the seventh day. Alterations in the components of mitochondria and microsomes of the lung were considerably different from those of the liver. The protein content of the lung increased to 1.18 (P less than 0.05)- and 1.14 (P less than 0.05)-fold that of the control during exposure to 10 and 4 ppm NO2, respectively. The succinate-cytochrome c reductase activity showed a reduced value, which was 73% (P less than 0.01) of the control level, 1 day after exposure to 10 ppm NO2, Subsequently, the activity increased to 1.14-fold that of the control during exposure to 10 (at the fifth day) and 4 ppm (at the fourth day) NO2. Components of microsomal electron-transport systems also showed a slightly elevated value during exposure to 4 ppm NO2. Seven days after exposure, the cytochrome P-450 content was decreased to 61% (P less than 0.01) of the control level, while other components were retained at control levels. A significant reduction in the cytochrome P-450 content was also observed at the exposure concentration of 1.2 ppm, but not of 0.4 ppm, at the seventh day.
mesh_terms: D000818:Animals; D001273:Atmosphere Exposure Chambers; D003577:Cytochrome P-450 Enzyme System / Q000032:analysis; D003573:Cytochrome b Group / Q000032:analysis; D004579:Electron Transport / Q000187:drug effects; D008168:Lung / Q000187:drug effects* / Q000201:enzymology; D008297:Male; D008862:Microsomes, Liver / Q000187:drug effects* / Q000201:enzymology; D009251:NADPH-Ferrihemoprotein Reductase / Q000037:antagonists & inhibitors; D009585:Nitrogen Dioxide / Q000494:pharmacology*; D051381:Rats; D013384:Succinate Cytochrome c Oxidoreductase / Q000037:antagonists & inhibitors
chemical_list: D003573:Cytochrome b Group; D003577:Cytochrome P-450 Enzyme System; D013384:Succinate Cytochrome c Oxidoreductase; D009251:NADPH-Ferrihemoprotein Reductase; D009585:Nitrogen Dioxide