Abstract
The reductive metabolism of 2-nitrofluorene, a carcinogenic air pollutant, in rat skin microsomes and cytosol was investigated. 2-Nitrofluorene was reduced to the corresponding amine by the microsomes with NADPH and by the cytosol with 2-hydroxypyrimidine or 4-hydroxypyrimidine under anaerobic conditions. The cytosolic activity was much higher than that of skin microsomes. The 2- or 4-hydroxypyrimidine-linked nitroreductase activity was inhibited by oxypurinol and (+/−)-8-(3-methoxy-4-phenylsulfinylphenyl) pyrazolo[1,5-a]-1,3,5-triazine-4(1H)-one (BOF-4272), inhibitors of xanthine oxidase, but not by menadione, chlorpromazine and isovanillin, inhibitors of aldehyde oxidase. When skin cytosol was applied to a DEAE-cellulose column, the fractions containing xanthine oxidase exhibited a marked 2-hydroxypyrimidine-linked nitroreductase activity. In contrast, the aldehyde oxidase fraction showed little activity. Nitroreductase fractions obtained by ion exchange chromatography showed a band in Western blotting analysis using anti-rat xanthine oxidase. Moreover, the xanthine oxidase fraction exhibited a significant nitroreductase activity in the presence of 2-hydroxypyrimidine, 4-hydroxypyrimidine or hypoxanthine, and these activities were inhibited by inhibitors of xanthine oxidase. These results indicated that reduction of 2-nitrofluorene in the skin was mainly catalyzed by xanthine oxidase.
Footnotes
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This work was supported by Grant-in-Aid for Scientific Research on Priority Area (13027256) from the Japanese Ministry of Education, Science, Sports and Culture, and Grant-in-Aid for Scientific Research (C13672343) from Japan Society for the Promotion of Science.
- Abbreviations used are::
- PAHs
- polycyclic aromatic hydrocarbons
- BOF-4272
- (+/−)-8-(3-methoxy-4-phenylsulfinylphenyl) pyrazolo[1,5-a]-1,3,5-triazine-4(1H)-one
- HPLC
- high-performance liquid chromatography
- Received September 23, 2002.
- Accepted December 18, 2002.
- The American Society for Pharmacology and Experimental Therapeutics
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