Exposure to benzo[a]pyrene of hepatic cytochrome P450 reductase null (HRN) and P450 reductase conditional null (RCN) mice: detection of benzo[a]pyrene diol epoxide-DNA adducts by immunohistochemistry and P-postlabelling

Volker M. Arlt, Miriam C. Poirier, Sarah E. Sykes, Kaarthik John, Michaela Moserova, Marie Stiborova, C. Roland Wolf, Colin J. Henderson, David H. Phillips

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    Benzo[a]pyrene (BaP) is a widespread environmental carcinogen activated by cytochrome P450 (P450) enzymes. In Hepatic P450 Reductase Null (HRN) and Reductase Conditional Null (RCN) mice, P450 oxidoreductase (Por) is deleted specifically in hepatocytes, resulting in the loss of essentially all hepatic P450 function. Treatment of HRN mice with a single i.p. or oral dose of BaP (12.5 or 125mg/kgbody weight) resulted in higher DNA adduct levels in liver (up to 10-fold) than in wild-type (WT) mice, indicating that hepatic P450s appear to be more important for BaP detoxification in vivo. Similar results were obtained in RCN mice. We tested whether differences between hepatocytes and non-hepatocytes in P450 activity may underlie the increased liver BaP-DNA binding in HRN mice. Cellular localisation by immunohistochemistry of BaP-DNA adducts showed that HRN mice have ample capacity for formation of BaP-DNA adducts in liver, indicating that the metabolic process does not result in the generation of a reactive species different from that formed in WT mice. However, increased protein expression of cytochrome b in hepatic microsomes of HRN relative to WT mice suggests that cytochrome b may modulate the P450-mediated bioactivation of BaP in HRN mice, partially substituting the function of Por.
    Original languageEnglish
    Pages (from-to)160-166
    Number of pages7
    JournalToxicology Letters
    Issue number2
    Publication statusPublished - 2012



    • Animals
    • Benzo(a)pyrene
    • Cytochrome P-450 CYP1A1
    • Cytochromes b5
    • DNA Adducts
    • DNA Damage
    • Female
    • Hepatocytes
    • Immunohistochemistry
    • Liver
    • Mice
    • Mice, Inbred C57BL
    • Mice, Knockout
    • Microsomes, Liver
    • NADPH-Ferrihemoprotein Reductase

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