Peroxidative metabolism of a carcinogen, N-hydroxy-N-2-fluorenylacetamide, by rat uterus and mammary gland in vitro.
Lactoperoxidase-catalyzed metabolism of N-hydroxy-N-2-fluorenylacetamide (N-OH-2-FAA) may be via one-electron oxidation to nitroxyl free radical which dismutates to equimolar N-acetoxy-N-2-fluorenylacetamide and 2-nitrosofluorene (2-NOF) and/or a Br(-)-dependent oxidative cleavage to 2-NOF. Hence, the 2-NOF:N-acetoxy-N-2-fluorenylacetamide ratios reflect the relative contributions of the two peroxidative pathways to the metabolism of N-OH-2-FAA. Peroxidative activities of rat uterus (UT) and mammary gland (MG) were extracted with a cationic detergent, cetyltrimethylammonium bromide (Cetab). MG extracts had 1 to 5% the specific activity of UT extracts when assayed with guaiacol as hydrogen donor. At 0.004% Cetab, which in the incubation media corresponds to the approximate physiological levels of 0.1 mM Br(-), oxidation of N-OH-2-FAA by UT extracts yielded a product ratio indicative of both peroxidative pathways with Br(-)-dependent oxidation prevailing. At 0.4% Cetab, one-electron oxidation was negligible and Br(-)-dependent conversion of N-OH-2-FAA to 2-NOF was markedly enhanced. At both 0.004 and 0.4% Cetab, MG extracts yielded only 2-NOF, suggesting solely Br(-)-dependent oxidation. With equivalent guaiacol units of peroxidative activities, MG extracts produced much lower amounts of 2-NOF than did UT extracts. The low specific activities of MG extracts necessitated the use of larger amounts of protein, which might have interfered with peroxidative metabolism. At 0.004% Cetab, formation of 2-NOF by the Br(-)-dependent pathway was greater at pH 5.5 than at 7.4. At acid pH, small amounts of 2-nitrofluorene were also formed by UT and MG extracts and could be attributed to further oxidation of 2-NOF. Peroxidative activities of the UT and MG extracts may be of granular leukocyte origin and their potential role in carcinogen activation and tumorigenesis is discussed.
D015073:2-Acetylaminofluorene / Q000031:analogs & derivatives*; D000818:Animals; D004247:DNA / Q000378:metabolism; D005260:Female; D006881:Hydroxyacetylaminofluorene / Q000378:metabolism*; D066298:In Vitro Techniques; D007784:Lactoperoxidase / Q000494:pharmacology; D008321:Mammary Glands, Animal / Q000378:metabolism*; D009603:Nitroso Compounds / Q000378:metabolism; D010084:Oxidation-Reduction; D010544:Peroxidases / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D014599:Uterus / Q000378:metabolism*
D009603:Nitroso Compounds; C012458:2-nitrosofluorene; D006881:Hydroxyacetylaminofluorene; D004247:DNA; D015073:2-Acetylaminofluorene; D007784:Lactoperoxidase; D010544:Peroxidases