Biomaterial Database

In vitro metabolism of 7,12-dimethylbenz[a]anthracene by rainbow trout liver microsomes and trout P450 isoforms. 1997

C L Miranda, and M C Henderson, and D E Williams, and D R Buhler

Department of Agricultural Chemistry, Oregon State University, Corvallis 97331, USA.

Liver microsomes from juvenile trout metabolized DMBA to unknown highly polar metabolites (X) and to DMBA-t-5,6-diol, DMBA-t-8,9-diol, 7-OHM-12-MBA, 7M-12-OHMBA, 2-OH-DMBA, 4-OH-DMBA, and trace amounts of DMBA-t-3,4-diol. Treatment of trout with beta-naphthoflavone (BNF) and isosafrole (ISF) increased the formation of these products except for the hydroxymethyl derivatives of DMBA. The production of DMBA-t-3,4-diol, 2-OH-DMBA, and 4-OH-DMBA was much greater in BNF-induced liver microsomes than that in ISF-induced liver microsomes. In contrast, the yield of DMBA-t-8,9-diol and 7-OHM-12-MBA was greater in ISF-induced microsomes than that in BNF-induced microsomes. Trout CYP1A1 (P450 LM4b) purified from BNF-treated trout catalyzed the formation of the same metabolites generated by BNF-induced microsomes in the presence of added human microsomal EH. The constitutive forms of P450 isolated from untreated trout such as P450s LMC3, LMC4, and LMC5, CYP2M1 (P450 LMC1), and CYP2K1 (P450 LMC2) did not produce any of the DMBA metabolites (except for DMBA-t-8,9-diol by CYP2K1) generated by the trout microsomes. Generation of DMBA-DNA and DMBA-protein adducts in vitro was enhanced by treatment of trout with BNF and by ISF to a lesser extent. Formation of adducts and DMBA diols by BNF-induced liver microsomes and by trout CYP1A1 was completely blocked by the CYP1A inhibitor ellipticine (100 microM). These results suggest that the BNF-inducible trout P450 (CYP1A), not the constitutive P450s, is the major catalyst for the biotransformation of DMBA to metabolites that bind to macromolecules.

UI	MeSH Term	Description	Entries
D007527	Isoenzymes	Structurally related forms of an enzyme. Each isoenzyme has the same mechanism and classification, but differs in its chemical, physical, or immunological characteristics.	Alloenzyme,Allozyme,Isoenzyme,Isozyme,Isozymes,Alloenzymes,Allozymes
D008862	Microsomes, Liver	Closed vesicles of fragmented endoplasmic reticulum created when liver cells or tissue are disrupted by homogenization. They may be smooth or rough.	Liver Microsomes,Liver Microsome,Microsome, Liver
D011506	Proteins	Linear POLYPEPTIDES that are synthesized on RIBOSOMES and may be further modified, crosslinked, cleaved, or assembled into complex proteins with several subunits. The specific sequence of AMINO ACIDS determines the shape the polypeptide will take, during PROTEIN FOLDING, and the function of the protein.	Gene Products, Protein,Gene Proteins,Protein,Protein Gene Products,Proteins, Gene
D002994	Clofibrate	A fibric acid derivative used in the treatment of HYPERLIPOPROTEINEMIA TYPE III and severe HYPERTRIGLYCERIDEMIA. (From Martindale, The Extra Pharmacopoeia, 30th ed, p986)	Athromidin,Atromid,Atromid S,Clofibric Acid, Ethyl Ester,Ethyl Chlorophenoxyisobutyrate,Miscleron,Miskleron,Chlorophenoxyisobutyrate, Ethyl
D003577	Cytochrome P-450 Enzyme System	A superfamily of hundreds of closely related HEMEPROTEINS found throughout the phylogenetic spectrum, from animals, plants, fungi, to bacteria. They include numerous complex monooxygenases (MIXED FUNCTION OXYGENASES). In animals, these P-450 enzymes serve two major functions: (1) biosynthesis of steroids, fatty acids, and bile acids; (2) metabolism of endogenous and a wide variety of exogenous substrates, such as toxins and drugs (BIOTRANSFORMATION). They are classified, according to their sequence similarities rather than functions, into CYP gene families (>40% homology) and subfamilies (>59% homology). For example, enzymes from the CYP1, CYP2, and CYP3 gene families are responsible for most drug metabolism.	Cytochrome P-450,Cytochrome P-450 Enzyme,Cytochrome P-450-Dependent Monooxygenase,P-450 Enzyme,P450 Enzyme,CYP450 Family,CYP450 Superfamily,Cytochrome P-450 Enzymes,Cytochrome P-450 Families,Cytochrome P-450 Monooxygenase,Cytochrome P-450 Oxygenase,Cytochrome P-450 Superfamily,Cytochrome P450,Cytochrome P450 Superfamily,Cytochrome p450 Families,P-450 Enzymes,P450 Enzymes,Cytochrome P 450,Cytochrome P 450 Dependent Monooxygenase,Cytochrome P 450 Enzyme,Cytochrome P 450 Enzyme System,Cytochrome P 450 Enzymes,Cytochrome P 450 Families,Cytochrome P 450 Monooxygenase,Cytochrome P 450 Oxygenase,Cytochrome P 450 Superfamily,Enzyme, Cytochrome P-450,Enzyme, P-450,Enzyme, P450,Enzymes, Cytochrome P-450,Enzymes, P-450,Enzymes, P450,Monooxygenase, Cytochrome P-450,Monooxygenase, Cytochrome P-450-Dependent,P 450 Enzyme,P 450 Enzymes,P-450 Enzyme, Cytochrome,P-450 Enzymes, Cytochrome,Superfamily, CYP450,Superfamily, Cytochrome P-450,Superfamily, Cytochrome P450
D003907	Dexamethasone	An anti-inflammatory 9-fluoro-glucocorticoid.	Hexadecadrol,Decaject,Decaject-L.A.,Decameth,Decaspray,Dexasone,Dexpak,Hexadrol,Maxidex,Methylfluorprednisolone,Millicorten,Oradexon,Decaject L.A.
D004357	Drug Synergism	The action of a drug in promoting or enhancing the effectiveness of another drug.	Drug Potentiation,Drug Augmentation,Augmentation, Drug,Augmentations, Drug,Drug Augmentations,Drug Potentiations,Drug Synergisms,Potentiation, Drug,Potentiations, Drug,Synergism, Drug,Synergisms, Drug
D004611	Ellipticines	Pyrido-CARBAZOLES originally discovered in the bark of OCHROSIA ELLIPTICA. They inhibit DNA and RNA synthesis and have immunosuppressive properties.
D004790	Enzyme Induction	An increase in the rate of synthesis of an enzyme due to the presence of an inducer which acts to derepress the gene responsible for enzyme synthesis.	Induction, Enzyme
D004791	Enzyme Inhibitors	Compounds or agents that combine with an enzyme in such a manner as to prevent the normal substrate-enzyme combination and the catalytic reaction.	Enzyme Inhibitor,Inhibitor, Enzyme,Inhibitors, Enzyme