Heterocyclic polycyclic aromatic hydrocarbon carcinogenesis: 7H-dibenzo[c,g]carbazole metabolism by microsomal enzymes from mouse and rat liver

The metabolism of dibenzo[c,g]carbazole (DBC), was studied in vitro using microsomal fractions of mouse and rat liver from animals, which were treated with 3-methylcholanthrene (MC). The separation of extractable metabolites by high pressure liquid chromatography (HPLC) and thin-layer chromatography...

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Bibliographic Details
Published in:	Chemico-biological interactions Vol. 35; no. 3; p. 267
Main Authors:	Perin, F, Dufour, M, Mispelter, J, Ekert, B, Künneke, C, Oesch, F, Zajdela, F
Format:	Journal Article
Language:	English
Published:	Ireland 01-06-1981
Subjects:	Animals Biotransformation Carbazoles - chemical synthesis Carbazoles - metabolism Carcinogens - metabolism Epoxide Hydrolases - metabolism Glutathione - pharmacology Heterocyclic Compounds - metabolism In Vitro Techniques Mice Microsomes, Liver - enzymology Polycyclic Compounds - metabolism Rats
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Summary:	The metabolism of dibenzo[c,g]carbazole (DBC), was studied in vitro using microsomal fractions of mouse and rat liver from animals, which were treated with 3-methylcholanthrene (MC). The separation of extractable metabolites by high pressure liquid chromatography (HPLC) and thin-layer chromatography (TLC) as well as identification of most of them by nuclear magnetic resonance, mass spectrometry and comparison with synthetically obtained products are described. The microsomes of both species produced the same twelve compounds of which the following have been identified: five monohydroxylated derivatives (phenols), the product of further oxidation of one of them, and a dihydrodiol. The 5-OH-DBC (60% including its spontaneously-formed dimer) and the 3-OH-DBC (14%) are the main metabolites. Three minor metabolites cochromatographed with synthetically prepared 2-OH-DBC, 4-OH-DBC and 6-OH-DBC. The dihydrodiol detectable in small quantity (4-6%) was tentatively identified as 3,4-dihydroxy-3,4-dihydro-DBC by the sensitivity of its formation to very low concentrations of the inhibitor of microsomal epoxide hydrolase, 1,1,1-trichloropropene oxide, by its molecular ion and major fragment in mass spectrometry and by its dehydration product 3-OH-DBC. No other dihydrodiols were detected. The qualitative and quantitative effects of various modulators of metabolism (enzyme inhibitors, apparently homogeneous epoxide hydrolase, glutathione, supernatant fraction) were investigated. The results are discussed with respect to possible ultimate carcinogens.
ISSN:	0009-2797
DOI:	10.1016/0009-2797(81)90002-8