Identification, functional characterization, and regulation of a new cytochrome P450 subfamily, the CYP2Ns.
AuthorsOleksiak MF,Wu S,Parker C,Karchner SI,Stegeman JJ,Zeldin DC
JournalThe Journal of biological chemistry
PubMed ID10644680
The screening of liver and heart cDNA libraries from the teleost Fundulus heteroclitus with degenerate oligonucleotide probes to conserved alpha-helical regions in mammalian P450s resulted in the identification of two cDNAs that together represent a novel P450 subfamily, the CYP2Ns. Northern analysis demonstrated that CYP2N1 transcripts are most abundant in ... More
Microtiter plate assays for inhibition of human, drug-metabolizing cytochromes P450.
AuthorsCrespi CL, Miller VP, Penman BW
JournalAnal Biochem
PubMed ID9177742
Drug metabolizing capacity in vitro and in vivo--I. Correlations between hepatic microsomal monooxygenase markers in beta-naphthoflavone-induced rats.
AuthorsMatthew DE, Houston JB
JournalBiochem Pharmacol
PubMed ID2386543
Relationships between and within in vivo and in vitro markers of drug oxidative metabolism have been investigated in rats displaying a wide range of hepatic microsomal monooxygenase activity due to prior treatment with various doses of the inducing agent beta-naphthoflavone (BNF). BNF induction produced large dose-related changes in the in ... More
Effect of suicide substrate on the metabolism of steroids and xenobiotics and on cytochrome P-450 apoproteins.
AuthorsTephly TR, Black KA, Green MD, Coffman BL, Dannan GA, Guengerich FP
JournalAdv Exp Med Biol
PubMed ID3766261
Cytosol-mediated reduction of resorufin: a method for measuring quinone oxidoreductase.
AuthorsNims RW, Prough RA, Lubet RA
JournalArch Biochem Biophys
PubMed ID6422857
The reduction of resorufin (7-hydroxyphenoxazone) fluorescence was catalyzed by enzymes present in the hepatic cytosol of rats and hamsters. This reaction was mediated by either NADH or NADPH, was completely inhibited by 10 microM dicumarol, and was not affected by anaerobic conditions (purging the reaction cuvette with nitrogen). The enzyme-mediated ... More
Monoclonal antibody-directed characterization of benzene, ethoxyresorufin and pentoxyresorufin metabolism in rat liver microsomes.
AuthorsNakajima T, Elovaara E, Park SS, Gelboin HV, Hietanen E, Vainio H
JournalBiochem Pharmacol
PubMed ID2403379
'The contribution of cytochrome P450IA, P450IIB, P450IICII and P450IIEI to the oxidative metabolism of benzene, 7-ethoxyresorufin and 7-pentoxyresorufin was investigated using monoclonal antibodies (MAb) in liver microsomes from fed, one-day fasted, phenobarbital (PB)-, 3-methylcholanthrene (MC)- and ethanol-treated rats. Overall catalytic activity varied with different pretreatments and thereby the contribution of ... More
3-methylcholanthrene-induced monooxygenase (O-deethylation) activity of human lymphocytes.
AuthorsBurke MD, Mayer RT, Kouri RE
JournalCancer Res
PubMed ID188547
'With a direct fluorescence assay, the levels of mixed-function oxidase activity were determined in mitogen-activated human lymphocytes. The O-deethylation of ethoxyresorufin to resorufin was used to quantitate mixed-function oxidase activity. Ethoxyresorufin O-deethylase activity was low to nondetectable in noninduced, mitogen-activated cells, but it was readily detected in 3-methylcholanthrene, mitogen-activated lymphocytes. ... More
Quantitative evaluation of hepatic cytochrome P4501A transcript, protein, and catalytic activity in the striped sea bream (Lithognathus mormyrus).
AuthorsTom M, Shmul M, Shefer E, Chen N, Slor H, Rinkevich B, Herut B
JournalEnviron Toxicol Chem
PubMed ID12959535
'Hepatic cytochrome P4501A (CYP1A) expression was partially characterized in the striped sea bream (Lithognathus mormyrus) from the Mediterranean coast of Israel as part of the process of establishing the CYP1A gene as an environmental biomarker. Reverse transcription-competitive polymerase chain reaction, competitive enzyme-linked immunosorbent assay, and ethoxyresorufin O-deethylase (EROD) assay were ... More
Induction of liver monooxygenases by beta-myrcene.
AuthorsDe-Oliveira AC, Ribeiro-Pinto LF, Otto SS, Gonçalves A, Paumgartten FJ
JournalToxicology
PubMed ID9458003
'Beta-Myrcene (MYR) is an acyclic monoterpene found in the essential oils of a variety of useful plants such as lemongrass (Cymbopogon citratus), hop, verbena, bay and others. MYR and essential oils containing this olefinic monoterpene are widely used as flavoring food additives, as fragrances in cosmetics and as scents in ... More
Regulation of CYP1A1 by indolo[3,2-b]carbazole in murine hepatoma cells.
AuthorsChen YH, Riby J, Srivastava P, Bartholomew J, Denison M, Bjeldanes L
JournalJ Biol Chem
PubMed ID7673247
'To determine the basis for unexpected differences in CYP1A1 inducing potencies and efficacies for the diet-derived indole derivative, indolo[3,2-b]carbazole (ICZ) and 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), we conducted a systematic analysis of events involved in the induced expression of CYP1A1 in murine hepatoma-derived cell lines (Hepa-1). In contrast to the effects of TCDD, ... More
Inhibition of NO-medicate responses by 7-ethoxyresorufin, a substrate and competitive inhibitor of cytochrome P450.
AuthorsLi CG, Rand MJ
JournalBr J Pharmacol
PubMed ID8733576
'1. The effects of 7-ethoxyresorufin (7-ER), which is a substrate for and competitive inhibitor of cytochrome P450, were studied on responses to nitric oxide (NO), the NO donors sodium nitroprusside (SNP) and glyceryl trinitrate (GTN), acetylcholine-induced endothelium-dependent relaxations of rat and rabbit aortic rings and nitrergic nerve stimulation-induced relaxations of ... More
Stereoselective and regioselective hydroxylation of warfarin and selective O-dealkylation of phenoxazone ethers in human placenta.
'The oxidative metabolism of warfarin and a series of phenoxazone ethers was studied in two groups of human placentas which exhibited high or low levels of aryl hydrocarbon hydroxylase (AHH). Warfarin metabolism was stereoselective (mean R/S = 2.48) for the R-enantiomer and regioselective for the 6- and 8- positions in ... More
Methoxyresorufin and benzyloxyresorufin: substrates preferentially metabolized by cytochromes P4501A2 and 2B, respectively, in the rat and mouse.
AuthorsNerurkar PV, Park SS, Thomas PE, Nims RW, Lubet RA
JournalBiochem Pharmacol
PubMed ID8373445
'The cytochrome P450 isozyme specificity for the O-dealkylation of methoxyresorufin (MTR) and benzyloxyresorufin (BZR) in the rat and mouse was investigated. The induction of various alkoxyresorufin O-dealkylation activities was measured in male F344/NCr rats exposed to 2,3,7,8-tetrachlorodibenzo-p-dioxin or 3,4,5,3',4',5'-hexachlorobiphenyl. MTR and ethoxyresorufin (ETR) O-dealkylation activities were induced 30- and 80-fold, ... More
Comparison of in vitro activities of biotransformation enzymes in pig, cattle, goat and sheep.
AuthorsSzotáková B, Baliharová V, Lamka J, Nozinová E, Wsól V, Velík J, Machala M, Neca J, Soucek P, Susová S, Skálová L
JournalRes Vet Sci
PubMed ID14659728
'In vitro activities of cytochromes P450 (7-alkyl/aryloxyresorufin dealkyl(aryl)ases, testosterone hydroxylase/oxidase, 6-chlorzoxazone hydroxylase, 7-methoxy-4-trifluoromethyl-coumarin demethylase, and lauric acid hydroxylases), reductases of carbonyl group (toward metyrapone, daunorubicin, glyceraldehyde, and 4-pyridine-carboxaldehyde) and conjugation enzymes (p-nitrophenol-UDP-glucuronosyl transferase, 1-chloro-2,4-dinitrobenzene glutathione-S-tranferase) in young adults, males, non-castrated (N=6) farm animals were studied and compared. Presence of proteins ... More
Determination of cytochrome P-448 activity in biological tissues.
AuthorsPhillipson CE, Godden PM, Lum PY, Ioannides C, Parke DV
JournalBiochem J
PubMed ID6087804
'Three enzymes used for the determination of cytochrome P-448 activity, namely aryl hydrocarbon hydroxylase, biphenyl 2-hydroxylase and ethoxyresorufin O-de-ethylase, were evaluated with respect to their specificity, sensitivity and inducibility. Purified cytochrome P-448 (LM4), but not cytochrome P-450 (LM2), catalysed the O-de-ethylation of ethoxyresorufin in a reaction that was markedly inhibited ... More
Intralobular localization of different cytochrome P-450 form dependent monooxygenase activities in the liver of normal and inducer-treated rats.
AuthorsSerasinghe P, Yamazaki H, Nishiguchi K, Serasinghe S, Nakanishi S
JournalInt J Biochem
PubMed ID1612185
'1. Isolated periportal (PP) and perivenous (PV) hepatocytes from normal and inducer-treated rat livers were used to examine the following: intralobular localization of cytochrome P-450IA, P-450IIB, P-450IIE and P-450IIIA dependent monooxygenase activities and effects of phenobarbital (PB), beta-naphthoflavone (BNF) and pregnenolone-16 alpha-carbonitrile (PCN) on the zonal induction of these monooxygenases. ... More
Arachidonic acid inhibits capacitative calcium entry in rat thymocytes and human neutrophils.
AuthorsAlonso-Torre SR, García-Sancho J
JournalBiochim Biophys Acta
PubMed ID9315617
'Emptying the intracellular Ca2+ stores by treatment with the endomembrane Ca2+-ATPase inhibitor thapsigargin activates capacitative Ca2+ entry (CCE). This can be evidenced in fura-2-loaded cells by an increase of [Ca2+]i or by an acceleration of Mn2+ entry. Micromolar concentrations of arachidonic acid inhibited CCE induced by treatment with thapsigargin in ... More
Resorufin inhibits the in vitro metabolism and mutagenesis of benzo(a)pyrene.
AuthorsJablonski JE, Sullivan PD
JournalBiochem Biophys Res Commun
PubMed ID2423085
'7-Hydroxyphenoxazin-3-one, commonly known as resorufin, strongly inhibits benzo(a)pyrene-induced mutation in the Ames bacterial reversion assay. The antimutagenic mechanism is due in part to redox cycling of resorufin with the concommitant transfer of reducing equivalents from NADPH to molecular oxygen. The diversion of electrons from cytochrome P-450 enzymes results in a ... More
7-Ethoxyresorufin-O-deethylase activity in human hair roots: a potential marker for toxifying species of cytochrome P-450 isozymes.
AuthorsMerk HF, Mukhtar H, Schutte B, Kaufmann I, Das M, Bickers DR
JournalBiochem Biophys Res Commun
PubMed ID3689370
'Assay systems for the evaluation of carcinogen interaction with human tissues are essential for assessing cancer risk. Human hair roots (HHR) are a readily obtainable epithelial tissue source that have been employed for investigating inherited enzyme activities. In this study HHR were found to possess cytochrome P-450-dependent 7-ethoxyresorufin-O-deethylase (ERD) activity ... More
Uroporphyria produced in mice by iron and 5-aminolaevulinic acid does not occur in Cyp1a2(-/-) null mutant mice.
AuthorsSinclair PR, Gorman N, Dalton T, Walton HS, Bement WJ, Sinclair JF, Smith AG, Nebert DW
JournalBiochem J
PubMed ID9461503
'In the present study we have investigated the putative requirement for the cytochrome P-450 isoform CYP1A2 in murine uroporphyria, by comparing Cyp1a2(-/-) knockout mice with Cyp1a2(+/+) wild-type mice. Uroporphyria was produced by injecting animals with iron-dextran and giving the porphyrin precursor 5-aminolaevulinic acid in the drinking water. Some animals also ... More
Redox cycling of resorufin catalyzed by rat liver microsomal NADPH-cytochrome P450 reductase.
AuthorsDutton DR, Reed GA, Parkinson A
JournalArch Biochem Biophys
PubMed ID2464338
'The O-dealkylation of 7-alkoxyresorufins to the highly fluorescent compound, resorufin (7-hydroxyphenoxazone), provides a rapid, sensitive, and convenient assay of certain forms of liver microsomal cytochrome P450. The results of this study indicate that NADPH-cytochrome P450 reductase catalyzes the reduction of resorufin (and the 7-alkoxyresorufins) to a colorless, nonfluorescent compound(s). The ... More
On the enzyme-inducing action of calcium antagonists.
AuthorsKoleva M, Stoytchev T
JournalArch Toxicol
PubMed ID8517787
'The effects of three calcium antagonists, nifedipine (NF), verapamil (V) and diltiazem (DL), on rat liver monooxygenases were studied. The drugs were administered in oral doses of 50, 40 and 30 mg/kg daily for 3 weeks in male Wistar rats. NF and V shortened the hexobarbital (HB) sleeping time and ... More
Characterization of the oxidase activity in mammalian catalase.
'Catalase is a highly conserved heme-containing antioxidant enzyme known for its ability to degrade hydrogen peroxide into water and oxygen. In low concentrations of hydrogen peroxide, the enzyme also exhibits peroxidase activity. We report that mammalian catalase also possesses oxidase activity. This activity, which is detected in purified catalases, cell ... More
Distribution of cytochrome P450 activities towards alkoxyresorufin derivatives in rat brain regions, subcellular fractions and isolated cerebral microvessels.
AuthorsPerrin R, Minn A, Ghersi-Egea JF, Grassiot MC, Siest G
JournalBiochem Pharmacol
PubMed ID2242042
'The regional and subcellular distributions of rat brain cytochrome P450 and cytochrome P450-dependent activities were examined. Cytochrome P450 was found to be mainly localized in mitochondria in all the six cerebral regions studied. The activities of the isoforms mostly implicated in drug metabolism, cytochromes P450 b and c, were measured ... More
Gill filament-based EROD assay for monitoring waterborne dioxin-like pollutants in fish.
AuthorsJönsson EM, Brandt I, Brunström B
JournalEnviron Sci Technol
PubMed ID12188363
'A sensitive, accurate, and straightforward way to determine basal and induced ethoxyresorufin O-deethylase (EROD) activities in gill filaments, using rainbow trout as model species, is described. Tip pieces of primary gill filaments were incubated in tissue culture plate wells containing HEPES-Cortland buffer supplemented with 7-ethoxyresorufin. Each well was sampled on ... More
A continuous fluorometric assay for cytochrome P-450-dependent mixed function oxidases using 3-cyano-7-ethoxycoumarin.
AuthorsWhite IN
JournalAnal Biochem
PubMed ID3189781
'A direct fluorometric procedure for the continuous determination of cytochrome P-450-dependent mixed function oxidases, using 3-cyano-7-ethoxycoumarin substrate, is described. The reaction product, 3-cyano-7-hydroxycoumarin, is fluorescent at neutral pH values (excitation and emission wavelength maxima: 408 and 450 nm, respectively). Using hepatic microsomal preparations from control rats, the enzyme(s) had an ... More
The cytochrome P-450 monooxygenase system of rabbit lung enzyme components, activities, and induction in the nonciliated bronchiolar epithelial (Clara) cell, alveolar type II cell, and alveolar macrophage.
AuthorsDomin BA, Devereux TR, Philpot RM
JournalMol Pharmacol
PubMed ID3092027
'Enzyme components and activities of the cytochrome P-450 monooxygenase system in microsomal preparations from the Clara cell, alveolar type II cell, and alveolar macrophage fractions isolated from lungs of untreated rabbits and rabbits treated with 2,3,7,8-tetrachlorodibenzo-p-dioxin were examined. Results are compared to those obtained with microsomal preparations from whole lung. ... More
An established light ear mutant (C57BL/6J-Pdeb(rd1) le) mouse cell line exhibits a block to secretion of lysosomal enzymes.
AuthorsDelprato A, Raghavan S, Lyerla TA
JournalExp Cell Res
PubMed ID10739679
'The hypopigment mutant mice, light ear, pallid, and beige, possess defects in melanosomes, lysosomes, and platelet dense granules, suggesting that these organelles share a common biogenesis and processing. Light ear and pallid mutants are animal models for Hermansky Pudlak syndrome, whereas the beige mouse is an animal model for Chediak ... More
Interactions among P450 enzymes when combined in reconstituted systems: formation of a 2B4-1A2 complex with a high affinity for NADPH-cytochrome P450 reductase.
AuthorsBackes WL, Batie CJ, Cawley GF
JournalBiochemistry
PubMed ID9737863
'The purpose of this study is to characterize the interactions among P450 1A2, P450 2B4, and P450 reductase in mixed reconstituted systems. Previously, our laboratory demonstrated that in the presence of certain substrates, 1A2 can influence the catalytic characteristics of 2B4 [Cawley et al. (1995) Biochemistry 34, 1244-1247]. The goal ... More
Glucose localization in maize ovaries when kernel number decreases at low water potential and sucrose is fed to the stems.
AuthorsMcLaughlin JE, Boyer JS
JournalAnn Bot (Lond)
PubMed ID15159218
'BACKGROUND AND AIMS: Around the time of anthesis, young ovary development in maize (Zea mays) is vulnerable to 2 or 3 d of water deficits that inhibit photosynthesis. Abortion can result, and fewer kernels are produced. A breakdown of stored ovary starch is associated with the abortion and was investigated ... More
Purification and characterization of cytochrome P-450-dependent arachidonic acid epoxygenase from human liver.
AuthorsLaniado-Schwartzman M, Davis KL, McGiff JC, Levere RD, Abraham NG
JournalJ Biol Chem
PubMed ID3123495
'A novel human liver cytochrome P-450 isozyme (P-450-AA), which catalyzes arachidonic acid epoxidation, has been purified to electrophoretic homogeneity from human liver. As judged spectrally, the newly described isozyme is low spin in the oxidized state, with a soret band at 415 nm and an increased maximum at 451 nm ... More
A microassay for measuring cytochrome P450IA1 and P450IIB1 activities in intact human and rat hepatocytes cultured on 96-well plates.
AuthorsDonato MT, Gómez-Lechón MJ, Castell JV
JournalAnal Biochem
PubMed ID8238878
'This study deals with the development of a sensitive and simple microassay for measuring cytochrome P450IA1 and P450IIB1 activities in intact human and rat hepatocytes. The method is based on the metabolism by cells cultured in microwells of appropriate substrates at noncytotoxic concentrations (8 microM 7-ethoxyresorufin and 15 microM 7-pentoxyresorufin). ... More
Colonic transit in rats: effect of ovariectomy, sex steroid hormones, and pregnancy.
AuthorsRyan JP, Bhojwani A
JournalAm J Physiol
PubMed ID3728676
'In vitro studies suggest that the female sex steroid hormones [estrogen (E) and progesterone (P)] can affect the myoelectric and mechanical activity of colonic smooth muscle. The present study was designed to examine the influence of the hormones on colonic transit in vivo. Transit was assessed by quantifying the distribution ... More
7-Alkoxyquinolines: new fluorescent substrates for cytochrome P450 monooxygenases.
'A series of 7-alkoxyquinolines was synthesized and tested as substrates with hepatic microsomes prepared from male Wistar rats. Microsomal O-dealkylation rates and kinetic constants were determined for the 7-alkoxyquinolines with microsomes from control, 3-methylcholanthrene (MC)-pretreated, and phenobarbitone (PB)-pretreated rats. Structure-activity relationship studies indicated that the 7-benzyloxyquinoline was the most rapidly ... More
Evaluation of alkoxyresorufins as fluorescent substrates for cytochrome P450 BM3 and site-directed mutants.
'In this study, the first fluorescent assay for bacterial cytochrome P450 BM3 (BM3) and mutants is described. BM3 mutants are potentially very versatile biocatalysts for the production of fine chemicals. A fluorescent assay would be very useful for the identification of nonnatural ligands in high-throughput inhibition assays. Because of the ... More
Characteristics of a microsomal cytochrome P-448-mediated reaction. Ethoxyresorufin O-de-ethylation.
AuthorsBurke MD, Prough RA, Mayer RT
JournalDrug Metab Dispos
PubMed ID13970
'Certain characteristics of ethoxyresorufin O-de-ethylation, as catalyzed by microsomes of liver, lung, and intestine of control and pretreated rats and hamsters, were studied. The results support previous suggestions that the reaction is catalyzed primarily by a 3-methyl-cholanthrene (MC)-inducible mono-oxygenase which has a 448-nm absorption maximum in the reduced-CO difference spectrum. ... More
Molecular dimensions of the substrate binding site of cytochrome P-448.
AuthorsLewis DF, Ioannides C, Parke DV
JournalBiochem Pharmacol
PubMed ID3729975
'The molecular geometries of specific substrates, inhibitors and inducers of cytochrome P-448 activity were determined using computer-graphic techniques for use in defining the molecular dimensions of the substrate binding site of this enzyme. Specific substrates of cytochrome P-448 are essentially planar molecules characterised by a small depth and a large ... More
Human adult hepatocytes in primary monolayer culture. Maintenance of mixed function oxidase and conjugation pathways of drug metabolism.
'The stabilities of several drug oxidation and conjugation pathways in human adult hepatocytes have been investigated during 72 hr culture. Cytochrome P-450-dependent mixed function oxidase was measured by the O-dealkylations of ethoxyresorufin (EROD), pentoxyresorufin (PROD) and benzyloxyresorufin (BROD), which are probes for different isozymes of cytochrome P-450 in the rat. ... More
Benzo[a]pyrene-resistant MCF-7 human breast cancer cells. A unique aryl hydrocarbon-nonresponsive clone.
AuthorsMoore M, Wang X, Lu YF, Wormke M, Craig A, Gerlach JH, Burghardt R, Barhoumi R, Safe S
JournalJ Biol Chem
PubMed ID7909315
'Wild-type MCF-7 human breast cancer cells were cultured for 3 months in 1 microM benzo[a]pyrene (BaP), and resistant clones were screened for inducibility of CYP1A1 gene expression by 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). One of the BaP-resistant (BaPR) clones exhibited unique genotypic expression which distinguished it from both wild-type and drug-resistant (AdrR) variant ... More
Inhibition and inactivation of murine hepatic ethoxy- and pentoxyresorufin O-dealkylase by naturally occurring coumarins.
AuthorsCai Y, Bennett D, Nair RV, Ceska O, Ashwood-Smith MJ, DiGiovanni J
JournalChem Res Toxicol
PubMed ID8117927
'The present study was designed to evaluate the effects of a series of natural coumarins on ethoxyresorufin O-dealkylase (EROD) and pentoxyresorufin O-dealkylase (PROD) activities in vitro using hepatic tissues from SENCAR mice. Fifteen different coumarins were examined for potential modulating activities. Several naturally occurring coumarins, found in the human diet, ... More
Xenobiotic metabolism by isolated rat small intestinal cells.
AuthorsGrafström R, Moldéus P, Andersson B, Orrenius S
JournalMed Biol
PubMed ID522515
'A rapid method for isolation of cells from the small intestine of the rat resulted in a preparation where 95--100% of the cells excluded NADH or trypan blue. Isolated intestinal cells catalyzed the cytochrome P-450 dependent metabolism of benzo(a)pyrene, harmine, ethoxyresorufin and ethoxycoumarin. Isolation of intestinal cells 24 hours after ... More
Genotoxicity of industrial dyes under the inductive effect of ethanol on monooxygenase system in mice.
AuthorsWronska-Nofer T, Wisniewska-Knypl J, Wyszynska K, Dziubaltowska E
JournalMutat Res
PubMed ID9294022
'The genotoxic effects of triarylmethane (Acid Green 16, C.I.44025) and arylmonoazo (Basic Orange 28, developed by Boruta Pigment Plant, Poland, C.I. undisclosed) dyes, were evaluated in Balb/C mice. Animals were fed for 6 days nutritionally adequate Portagen liquid diet (1 kcal/ml) or isocaloric alcoholic diet containing 5% (w/v) ethanol (36% ... More
7-Ethoxycoumarin and 7-ethoxyresorufin O-deethylase in human foetal and adult liver: studies with monoclonal antibodies.
AuthorsPacifici GM, Park SS, Gelboin HV, Rane A
JournalPharmacol Toxicol
PubMed ID3261011
'The 7-ethoxycoumarin and 7-ethoxyresorufin O-deethylase activities were investigated in the microsomal fractions from 5 human adult and 3 foetal livers and 5 human foetal adrenals. The enzyme activity expressed as pmol/min. per mg microsomal protein was higher with 7-ethoxyresorufin as substrate in all investigated specimens with average values (+/- S.E.M.) ... More
Polycyclic aromatic hydrocarbons cause hepatic porphyria in iron-loaded C57BL/10 mice: comparison of uroporphyrinogen decarboxylase inhibition with induction of alkoxyphenoxazone dealkylations.
AuthorsFrancis JE, Smith AG
JournalBiochem Biophys Res Commun
PubMed ID3606611
'Multiple doses of beta-naphthoflavone to iron-loaded C57BL/10ScSn mice for 6 weeks caused inhibition of hepatic uroporphyrinogen decarboxylase and a porphyria indistinguishable from that previously only reported for polyhalogenated aromatic chemicals. beta-Naphthoflavone and other polycyclic aromatic hydrocarbon inducers of cytochrome P1-450-mediated ethoxyphenoxazone deethylation (ethoxyresorufin deethylase), benzo[a]pyrene, benz[a]anthracene, dibenz[ah]anthracene, 3-methylcholanthrene and alpha-naphthoflavone, ... More
Activity of aldrinepoxidase, 7-ethoxycoumarin-O-deethylase and 7-ethoxyresorufin-O-deethylase during the development of chick embryos in ovo.
AuthorsHeinrich-Hirsch B, Hofmann D, Webb J, Neubert D
JournalArch Toxicol
PubMed ID2350231
'Since the chick embryo in ovo is susceptible to the action of some agents needing metabolic activation we studied the development of the activity of cytochrome P450-dependent monooxygenases in embryo/fetal tissue. The activities of aldrinepoxidase (AE), 7-ethoxycoumarin-O-deethylase (ECOD) and 7-ethoxyresorufin-O-deethylase (EROD) were measured in whole embryos, liver and yolk sac ... More
Differential effects of phenobarbitone and 3-methylcholanthrene induction on the hepatic microsomal metabolism and cytochrome P-450-binding of phenoxazone and a homologous series of its n-alkyl ethers (alkoxyresorufins).
AuthorsBurke MD, Mayer RT
JournalChem Biol Interact
PubMed ID6883573
'The metabolism and cytochrome P-450-binding of phenoxazone and a homologous series of its n-alkyl ethers (1-8C) was studied in hepatic microsomes of control, phenobarbitone-pretreated (PB) and 3-methylcholanthrene-pretreated (3MC) C57/BL10 mice. Phenoxazone and its ethers were hydroxylated and O-dealkylated respectively to a common metabolite, resorufin. The three categories of microsomes differed ... More
Dealkylation of pentoxyresorufin: a rapid and sensitive assay for measuring induction of cytochrome(s) P-450 by phenobarbital and other xenobiotics in the rat.
'The O-dealkylation of pentoxyresorufin (7-pentoxyphenoxazone) by rat liver microsomes was examined. The reaction appeared highly specific for certain phenobarbital inducible forms of cytochrome P-450 and was increased 95- to 140-fold by animal pretreatment with phenobarbital (75 mg/kg/day, four ip injections) and approximately 50-fold by Aroclor 1254 (500 mg/kg, one ip ... More
Ethoxy-, pentoxy- and benzyloxyphenoxazones and homologues: a series of substrates to distinguish between different induced cytochromes P-450.
'The individual members of a homologous series of phenoxazone ethers related to ethoxyresorufin were O-dealkylated, and the parent compound phenoxazone was ring-hydroxylated, each at different rates with hepatic microsomes of untreated rats. A structure-activity relationship (SAR) was plotted, relating the rate of O-dealkylation to the length and type of the ... More
Characterization and identification of a pyrazole-inducible form of cytochrome P-450.
AuthorsPalakodety RB, Clejan LA, Krikun G, Feierman DE, Cederbaum AI
JournalJ Biol Chem
PubMed ID3335529
'In vivo administration of the alcohol dehydrogenase inhibitor pyrazole induces a cytochrome P-450 isozyme. The pyrazole-inducible cytochrome P-450 has been purified from rat livers to electrophoretic homogeneity and its biochemical, spectral, and immunological properties characterized. The final preparation had a specific content of 11 nmol of cytochrome P-450/mg of protein. ... More
Kinetics of substrate reaction in the course of hydroperoxide-mediated inactivation of cytochrome P450 1A1.
AuthorsYu XC, Liang C, Strobel HW
JournalBiochemistry
PubMed ID8639571
'A schematic kinetic model is proposed for the hydroperoxide-mediated substrate reaction and cytochrome P450 inactivation. From the model, the relationships between the product concentration at infinite time (P infinity), the apparent rate constant of P450 inactivation (A), and the substrate concentrations are predicted, and the predictions were experimentally examined. The ... More
Electron flow and complex formation during cytochrome P-450-catalyzed hydroxylation reactions in reconstituted membrane vesicles.
AuthorsIngelman-Sundberg M, Johansson I
JournalActa Chem Scand B
PubMed ID6442087
Genetic evidence for many unique liver microsomal P-450-mediated monooxygenase activities in heterogeneic stock mice.
AuthorsLang MA, Gielen JE, Nebert DW
JournalJ Biol Chem
PubMed ID7298645
Further characterization of the expression in liver and catalytic activity of CYP2B6.
AuthorsEkins S, Vandenbranden M, Ring BJ, Gillespie JS, Yang TJ, Gelboin HV, Wrighton SA
JournalJ Pharmacol Exp Ther
PubMed ID9732386
'Previous studies in this laboratory have determined the lack of specificity of several antibody and substrate probes of CYP2B6. The goals of the current study were to examine the expression of CYP2B6 in a bank of human liver microsome (HLM) samples using a new specific monoclonal antibody (MAb 49-10-20) and ... More
Use of 7-alkoxyphenoxazones, 7-alkoxycoumarins and 7-alkoxyquinolines as fluorescent substrates for rainbow trout hepatic microsomes after treatment with various inducers.
'Various fluorescent substrates have been used as specific indicators of induction or activity of different cytochrome P450 isozymes in both fish and mammalian species. In an attempt to identify additional definitive fluorescent substrates for use in fish, we examined a series of 7-alkoxyphenoxazones, 7-alkoxycoumarins and 7-alkoxyquinolines as substrates in O-dealkylation ... More
cAMP-dependent negative regulation of rat aldehyde dehydrogenase class 3 gene expression.
AuthorsXiao G, Falkner KC, Xie Y, Lindahl RG, Prough RA
JournalJ Biol Chem
PubMed ID9013560
'We investigated the inhibitory effects of intracellular cyclic adenosine monophosphate (cAMP) levels in regulating class 3 aldehyde dehydrogenase (aldh3) gene expression using cultures of primary rat hepatocytes and transient transfection experiments with HepG2 cells. In addition to regulation by an Ah receptor-dependent mechanism, expression of many members of the Ah ... More
Oxidative and conjugative metabolism of xenobiotics by livers of cattle, sheep, swine and rats.
AuthorsSmith GS, Watkins JB, Thompson TN, Rozman K, Klaassen CD
JournalJ Anim Sci
PubMed ID6423601
'Homogenate preparations from fresh livers of cattle, sheep, swine and rats were assayed for microsomal cytochrome P-450 content, for mixed-function oxidase activities and for a wide array of conjugative activities using numerous xenobiotic substrates. Results show that hepatic enzymatic capabilities toward xenobiotics do not parallel phylogenetic classifications, thus strengthening the ... More
Drug metabolizing capacity in vitro and in vivo--II. Correlations between hepatic microsomal monooxygenase markers in phenobarbital-induced rats.
AuthorsMatthew DE, Houston JB
JournalBiochem Pharmacol
PubMed ID2386544
'Pretreatment with various doses of phenobarbital (PB) has been used to create a pool of rats with a wide range of hepatic microsomal monooxygenase activity to systematically examine relationships between and within in vivo and in vitro markers. The in vivo clearance of tolbutamide (TOL), theophylline (TH), antipyrine (AP) and ... More
Selection and characterization of human cytochrome P450 1A2 mutants with altered catalytic properties.
AuthorsParikh A, Josephy PD, Guengerich FP
JournalBiochemistry
PubMed ID10220313
'Random mutagenesis is an approach that has the potential to provide useful information about cytochrome P450 (P450) enzymes but has not been extensively used to date. We applied our previously developed systems for generation of random libraries of human P450 1A2 with the putative substrate recognition sequences mutated (individual residues) ... More
Suppression of levels of phenobarbital-inducible rat liver cytochrome P-450 by pituitary hormone.
AuthorsYamazoe Y, Shimada M, Murayama N, Kato R
JournalJ Biol Chem
PubMed ID3584119
'The effect of pituitary factor on the constitutive and inducible levels of hepatic phenobarbital (PB)-inducible major cytochrome P-450, P-450b and P-450e, in male and female rat livers was studied by immunoblot analyses. Although only trace amounts (approximately 4 pmol/mg protein) of P-450b and P-450e were detected in untreated adult rats, ... More
Inhibition of nitrovasodilator- and acetylcholine-induced relaxation and cyclic GMP accumulation by the cytochrome P-450 substrate, 7-ethoxyresorufin.
AuthorsBennett BM, McDonald BJ, Nigam R, Long PG, Simon WC
JournalCan J Physiol Pharmacol
PubMed ID1362924
'We examined the effect of the cytochrome P-450 substrate, 7-ethoxyresorufin (7-ER), and its corresponding product, resorufin, on nitrovasodilator- and endothelium-dependent relaxation of isolated rat aorta. The EC50 value for glyceryl trinitrate (GTN) induced relaxation was increased over 100-fold by 7-ER and less than 3-fold by resorufin. The EC50 value for ... More
Oxidative biotransformation of benzo(a)pyrene by human lung microsomal fractions prepared from surgical specimens.
AuthorsSípal Z, Ahlenius T, Bergstrand A, Rodriquez L, Jakobsson SW
JournalXenobiotica
PubMed ID532213
'1. Microsomal fractions were prepared from 15--50 g specimens of human lung tissue (mostly alveolar) obtained at surgical resections of 13 middle-aged male patients suffering from different pulmonary tumours. Marker enzyme assays indicated that the frations contained about 25% of the endoplasmic reticulum of the homogenate and about 10% of ... More
Simultaneous measurement of cytochrome P4501A catalytic activity and total protein concentration with a fluorescence plate reader.
AuthorsKennedy SW, Jones SP
JournalAnal Biochem
PubMed ID7856852
'A method for simultaneous measurement of the cytochrome P4501A-associated enzyme, ethoxyresorufin-O-deethylase (EROD), and total protein concentration in liver microsomes is described. EROD assays were carried out in multiwell plates, and the fluorescent product (resorufin) and total proteins were quantified within the same wells with a fluorescence plate reader. Fluorescamine was ... More
Induction of liver monooxygenases by annatto and bixin in female rats.
AuthorsDe-Oliveira AC, Silva IB, Manhaes-Rocha DA, Paumgartten FJ
JournalBraz J Med Biol Res
PubMed ID12532234
'Annatto or urucum is an orange-yellow dye obtained from Bixa orellana seeds. It has been used as a natural dye in a variety of food products, drugs and cosmetics, and also in Brazilian cuisine as a condiment (''colorau''). Bixin, a carotenoid devoid of provitamin A activity, is the main pigment ... More
Continuous fluorometric assay of phenol sulfotransferase.
AuthorsBeckmann JD
JournalAnal Biochem
PubMed ID1785696
'Phenol sulfotransferases (EC 2.8.2.1) catalyze the sulfation of the acceptor hydroxyl group using 3''-phosphoadenosine 5''-phosphosulfate (PAPS) as the donor substrate. Previous assays of these enzymes, which exhibit varied acceptor substrate specificities, have required termination of the catalysis followed by isolation and quantitation of formed sulfate ester. In this report, the ... More
A microassay for the detection of low levels of cytochrome P450 O-deethylation activities with alkoxyresorufin substrates.
'A microfluorometric method for the detection of low levels of cytochrome P450 was developed to increase the sensitivity of the assay, since a low level of CYP450 associated enzymatic activities was expected in human placenta tissues and small samples of placenta (approximately 10 g) could be easily collected, stored and ... More
The nature of microsomal monooxygenase inhibition by cimetidine.
AuthorsWinzor DJ, Ioannoni B, Reilly PE
JournalBiochem Pharmacol
PubMed ID3729972
'A kinetic investigation of the inhibitory effect of cimetidine on the O-dealkylation of 7-ethoxyresorufin by rat liver microsomes has yielded linear Lineweaver-Burk plots which intersect in the second quadrant. Though technically compatible with non-competitive inhibition, the results are shown to be readily explained by the more realistic molecular concept of ... More
Multiple forms of cytochrome P-450 related to forms induced marginally by phenobarbital. Differences in structure and in the metabolism of alkoxyresorufins.
'The properties of five structurally related forms of cytochrome P-450 (PB1a, PB1b, PB2a, PB2b and PB2d) isolated from rats treated with phenobarbital have been compared with two forms isolated previously now termed ''PB1c'' and ''PB2c''. These enzymes were characterized by their marginal inducibility by phenobarbital and are clearly distinguishable from ... More
Human placental cytochrome P450 and quinone reductase enzyme induction in relation to maternal smoking.
'Components of cigarette smoke such as cadmium and polycyclic aromatic hydrocarbons have been shown to induce quinone reductase (QR) activity in placental explants. This study examines the relationship of maternal smoking habit and maternal plasma cotinine concentration with the activities in vitro of both QR and the cytochrome P450 (CYP1A) ... More
Microfluorimetric analysis of the cytochrome P448 associated, ethoxyresorufin O-deethylase activities of individual isolated rat hepatocytes.
AuthorsBurke MD, Hallman H
JournalBiochem Pharmacol
PubMed ID697897
Multiple forms of noninduced rat liver cytochrome P-450. Metabolism of 1-(4'-ethylphenoxy)-3,7-dimethyl-6,7-epoxy-trans-2-octene by reconstituted preparations.
AuthorsAgosin M, Morello A, White R, Repetto Y, Pedemonte J
JournalJ Biol Chem
PubMed ID573759
The effect of albumin on the metabolism of ethoxyresorufin through O-deethylation and sulphate-conjugation using isolated rat hepatocytes.
AuthorsBurke MD, Orrenius S
JournalBiochem Pharmacol
PubMed ID697896
Cytosol-mediated reduction of resorufin fluorescence: effects on the ethoxyresorufin O-deethylase (ETR) assay.
AuthorsNims RW, Lubet RA
JournalBiochem Pharmacol
PubMed ID6830615
Ethoxyresorufin: direct fluorimetric assay of a microsomal O-dealkylation which is preferentially inducible by 3-methylcholanthrene.
AuthorsBurke MD, Mayer RT
JournalDrug Metab Dispos
PubMed ID4155680
Multiple forms of ethoxyresorufin O-de-ethylase and benzphetamine N-demethylase in solubilized and partially resolved rat liver cytochromes P-450.
AuthorsWarner M, Neims AH
JournalDrug Metab Dispos
PubMed ID38092
A rapid method for assaying the metabolism of 7-ethoxyresorufin by microsomal subcellular fractions.
AuthorsPohl RJ, Fouts JR
JournalAnal Biochem
PubMed ID6776841
Expressing the specificity and the potency of cytochrome P-450 inducers toward 7-ethoxyresorufin.
AuthorsPaolini M, Forti GC, Bauer C
JournalDrug Metab Dispos
PubMed ID1981700
Direct fluorometric methods for measuring mixed function oxidase activity.
AuthorsPrough RA, Burke MD, Mayer RT
JournalMethods Enzymol
PubMed ID672641
A resorufin-based fluorescent assay for quantifying NADH.
AuthorsBatchelor RH, Zhou M
JournalAnal Biochem
PubMed ID12018954
Inhibition of hepatic and cutaneous biotransformation of resorufin ethers following intraperitoneal administration of 1-aminobenzotriazole.
AuthorsOldfield NF, Mortillo M, Garland WA, Mico BA
JournalPharm Res
PubMed ID1409385
O-dealkylation of resorufin ethers as an indicator of hepatic cytochrome P-450 isoenzyme induction in the cotton rat (Sigmodon hispidus): a method for monitoring environmental contamination.
AuthorsElangbam CS, Qualls CW, Lochmiller RL
JournalBull Environ Contam Toxicol
PubMed ID1932860
Metabolism of alkoxyphenoxazones by channel catfish liver microsomes: effects of phenobarbital, Aroclor 1254 and 3-methylcholanthrene.
AuthorsAnkley GT, Reinert RE, Mayer RT, Burke MD, Agosin M
JournalBiochem Pharmacol
PubMed ID3109440
Ethoxyresorufin O-deethylation by human liver microsomes.
AuthorsWilliams FM, Mutch E, Woodhouse KW, Lambert D, Rawlins MD
JournalBr J Clin Pharmacol
PubMed ID3768238
As a substrate for human liver microsomes, ethoxyresorufin appears to be metabolised by a group of cytochrome P450 isoenzymes which are inducible by cigarette smoking. Kinetic studies in microsomes from four human livers indicate that only one enzyme component is involved over the full substrate range. Ethoxyresorufin O-deethylation activity at ... More
Efficient analysis of cytochrome P4501A catalytic activity, porphyrins, and total proteins in chicken embryo hepatocyte cultures with a fluorescence plate reader.
AuthorsKennedy SW, Jones SP, Bastien LJ
JournalAnal Biochem
PubMed ID7793639
An efficient method for measuring polychlorinated biphenyl-mediated induction of cytochrome P4501A, using the ethoxyresorufin-O-deethylase (EROD) assay, and total porphyrins in chicken embryo hepatocyte cultures is described. Hepatocytes were cultured in 48-well plates, assays were carried out within the wells, and concentrations of the product of the EROD reaction (resorufin), porphyrins, ... More
A fluorescent cell-based assay for cytochrome P-450 isozyme 1A2 induction and inhibition.
AuthorsKelly JH, Sussman NL
JournalJ Biomol Screen
PubMed ID10992045
High throughput lead optimization requires simple, homogeneous cell-based assays capable of defining the druglike properties of first-round screening hits. Induction and inhibition of the Phase I drug-metabolizing enzymes are central to this process. We report here an assay for induction and inhibition of cytochrome P-450 (CYP) isozyme 1A2 that meets ... More
Automation of the resazurin reduction test using fluorometry of microtitration trays.
AuthorsAli-Vehmas T, Louhi M, Sandholm M
JournalZentralbl Veterinarmed B
PubMed ID1927150
Microtitration plate technique and -fluorometry was applied to automate the resazurin reduction test for monitoring bacterial numbers in broth cultures and milk. The effect of resazurin and resorufin concentration, bacterial species, growth medium, pH, and redox potential on the fluorescence response was studied. The timing of the appearance of maximum ... More
Ethoxyresorufin-O-deethylase and porphyrin analysis in chicken embryo hepatocyte cultures with a fluorescence multiwell plate reader.
AuthorsKennedy SW, Lorenzen A, James CA, Collins BT
JournalAnal Biochem
PubMed ID8323021
Rapid and sensitive methods for measuring ethoxyresorufin-O-deethylase (EROD) induction and total intracellular porphyrin accumulation in cultured chicken embryo hepatocytes exposed to polychlorinated biphenyls (PCBs) and 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) are described. Cells were cultured in 48-well cell culture plates, and EROD assays were carried out directly within the wells. EROD activity and ... More
The effect of reciprocal active site mutations in human cytochromes P450 1A1 and 1A2 on alkoxyresorufin metabolism.
Five reciprocal active site mutants of P450 1A1 and 1A2 and an additional mutant, Val/Leu-382 --> Ala, were constructed, expressed in Escherichia coli, and purified by Ni-NTA affinity chromatography. In nearly every case, the residue replacement led to loss of 7-methoxy- and 7-ethoxyresorufin O-dealkylase activity compared to the wild-type enzymes, ... More
Induction of O-deethylase activity as an index to exposure to coal-derived products and trace environmental pollutants.
AuthorsBostick WD, Kao J, Holland JM, Mrochek JE
JournalClin Chem
PubMed ID6973420
The metabolism of the synthetic substrate 7-ethoxyresorufin is a selective measure of the activity of cytochrome P-448 monooxygenase, the subset of cytochrome P-450-mediated enzymes preferentially induced by polycyclic aromatic hydrocarbons and related compounds. 7-Ethoxycoumarin metabolism, on the other hand, reflects total (nonselective) cytochrome P-450 monooxygenase activity. Either substrate yields a ... More
Direct influence of S9 liver homogenate on fluorescence signals: impact on practical applications in a bacterial genotoxicity assay.
AuthorsDreier J, Breitmaier EB, Gocke E, Apfel CM, Page MG
JournalMutat Res
PubMed ID11719102
Assays based on the bacterial SOS-response offer the possibility of automatization of genotoxicity testing for screening of large compound libraries. While existing assays use colorimetric detection or luminescence read-out, we describe here the use of a fluorescence-based system to achieve high sensitivity of detection required for assay miniaturization. Three commonly ... More
Induction of CYP1A1 by beta-naphthoflavone in IEC-18 rat intestinal epithelial cells and potentiation of induction by dibutyryl cAMP.
AuthorsZhang QY, He W, Dunbar D, Kaminsky L
JournalBiochem Biophys Res Commun
PubMed ID9168901
We have examined the inducibility of CYP1A1 by beta-naphthoflavone (BNF) in a rat intestinal epithelial cell line, IEC-18, and the associated interaction between cAMP and BNF. CYP1A1 was not constitutively expressed in IEC-18 cells. Upon treatment with BNF, CYP1A1 RNA, protein, and microsomal 7-ethoxyresorufin O-deethylase activity were detected. Treatment with ... More
High-level expression of functional human cytochrome P450 1A2 in Escherichia coli.
Enzymatically active human cytochrome P450 1A2 was expressed in Escherichia coli utilizing the pCWori+ vector containing a modified cDNA. The coding sequence for the NH2-terminal region of the protein was modified by the alignment and substitution of a 27 bp segment from a modified bovine P450 17A1 cDNA onto the ... More
Cytochrome P-450-dependent mixed-function oxidase and glutathione S-transferase activities in spontaneous obesity-diabetes.
AuthorsBarnett CR, Abbott RA, Bailey CJ, Flatt PR, Ioannides C
JournalBiochem Pharmacol
PubMed ID1575780
The effect of non-insulin-dependent diabetes on the hepatic microsomal cytochrome P450-dependent mixed-function oxidase system and on cytosolic glutathione S-transferase activity was determined using the spontaneously obese-diabetic (ob/ob) mouse model. The activities of the xenobiotic-metabolizing cytochrome P450 proteins were monitored by the use of chemical probes. Non-insulin-dependent diabetes did not influence ... More
Pre-translational induction of pentoxyresorufin O-depentylase by pyridine.
AuthorsPark KS, Sohn DH, Veech RL, Song BJ
JournalBiochem Biophys Res Commun
PubMed ID1610360
Pentoxyresorufin O-depentylase activity, mainly associated with phenobarbital-inducible cytochrome P450IIB1 (designated CYP2B1), was increased after a single treatment of pyridine (250 mg/kg, i.p.), and further increased by repeated treatments for 5 days. The catalytic activity and immunoreactive protein of CYP2B recognized by polyclonal antibodies were significantly induced by a relatively high ... More
Interaction of chlormezanone enantiomers with rat liver microsomes.
AuthorsKlinger W, Oelschläger H, Rothley D, Karge E, Seeling A
JournalEur J Drug Metab Pharmacokinet
PubMed ID10412893
Both chlormezanone enantiomers, for the first time obtained by enantiospecific HPLC with a 100% yield, bind to oxidized cytochrome P-450 in rat liver microsomes with a binding curve according to type I, similar to hexobarbital but less pronounced. There are no differences between the binding curves of the two enantiomers. ... More
Conformational change of cytochrome P450 1A2 induced by sodium chloride.
AuthorsYun CH, Song M, Ahn T, Kim H
JournalJ Biol Chem
PubMed ID8940137
Recently, it was reported that the activity of rabbit P450 1A2 is markedly increased at elevated sodium phosphate concentration. Here, the possible structural change of rabbit P450 1A2 accompanying the NaCl-induced increase in its enzyme activity is investigated by fluorescence spectroscopy, circular dichroism, and absorption spectroscopy. It was found that ... More
Substrate specificity of the mouse skin mixed-function oxidase system.
AuthorsRettie AE, Williams FM, Rawlins MD
JournalXenobiotica
PubMed ID3705617
The metabolism of nine model substrates for the mixed-function oxidase system was studied in skin and liver microsomes from Balb/C mice. Rates of skin metabolism per mg microsomal protein ranged from 0.5-15% of liver rates depending on the substrate. Relative to liver, mouse skin preferentially metabolized ethoxyresorufin, benzo[alpha]pyrene and diphenyloxazole ... More
Separation of two forms of cytochrome P-450 with aryl hydrocarbon hydroxylase activity from intestinal mucosa microsomes of rabbits treated with 3-methylcholanthrene.
AuthorsIchihara K, Ishihara K, Kaku M, Ogita K, Yamamoto S, Kusunose M
JournalBiochem Int
PubMed ID6679338
Two forms of cytochrome P-450, designated P-448a and P-448b, were purified from intestinal mucosa microsomes of rabbits treated with 3-methylcholanthrene. Both the cytochromes had absorption maxima at 448 nm in the carbon monoxide-reduced difference spectra. They exhibited comparable catalytic activities with benzo(a)pyrene, 7-ethoxycoumarin, and 7-ethoxyresorufin, when reconstituted with hepatic NADPH-cytochrome ... More
The excited-state interaction of resazurin and resorufin with amines in aqueous solutions. Photophysics and photochemical reactions.
The photophysics and photochemical behavior of the phenoxazin-3-one dyes, resazurin and resorufin, have been studied in aqueous solutions. The irradiation of resazurin in the presence of amines leads to deoxygenation of the N-oxide group, giving resorufin. This photoreaction is highly dependent on the amine structure and is efficient only in ... More
Induction of cytochrome P-450 isoenzymes in cultured monkey hepatocytes.
AuthorsNishibe Y, Hirata M
JournalInt J Biochem Cell Biol
PubMed ID7780832
The effect of phenobarbital (PB), beta-naphthoflavone (beta-NF) and rifampicin (Rif) on the drug-metabolizing activity of cultured squirrel monkey hepatocytes was examined. The drug metabolizing activity (e.g. alkoxycoumarin dealkylase or steroid hydroxylase) gradually decreased during the culture period with 40-70% activity remaining at 72 hr. When 0.5 mM PB was added ... More
Induction of cytochrome P-448 activity as exemplified by the O-deethylation of ethoxyresorufin. Effects of dose, sex, tissue and animal species.
AuthorsIwasaki K, Lum PY, Ioannides C, Parke DV
JournalBiochem Pharmacol
PubMed ID3778512
The effects of tissue, sex, animal species and dose on the induction of cytochrome P-448 activity by various inducing agents were investigated using O-ethoxyresorufin as a model substrate. The liver was by far more effective in catalysing the O-deethylation of ethoxyresorufin (EROD) than the lung and kidney. The extent of ... More