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Clearance and clearance inhibition of the HIV-1 protease inhibitors ritonavir and saquinavir in sandwich-cultured rat hepatocytes and rat microsomes

Treijtel, N. (author), Eijkeren, J.C.H.v. (author), Nijmeijer, S. (author), van der Greef de - Sandt, I.C.J. (author), Freidig, A.P. (author), TNO Kwaliteit van Leven (author)

The metabolism and active transport of ritonavir and saquinavir were studied using sandwich-cultured rat hepatoyctes and rat liver microsomes. For ritonavir four comparable metabolites were observed in the sandwich-culture and in microsomes. For saquinavir eight metabolites were observed in sandwich-culture and 14 different metabolites in...

article 2009

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Protein adduct formation by glucuronide metabolites of permethrin

Noort, D. (author), van Zuylen, A. (author), Fidder, A. (author), van Ommen, B. (author), Hulst, A.G. (author), TNO Defensie en Veiligheid (author)

Biomonitoring of exposure to the insecticide permethrin is usually performed by analysis of its urinary metabolites 3-phenoxybenzoic acid (3-PBA) or cis/trans-3-(2,2-dichlorovinyl)-2,2-dimethylcyclopropane-1-carboxylic acid (Cl2CA). We are engaged in the development of a methodology to assess the cumulative internal dose of exposure to...

article 2008

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Liquid chromatography/tandem mass spectrometry detection of covalent binding of acetaminophen to human serum albumin

Damsten, M.C. (author), Commandeur, J.N.M. (author), Fidder, A. (author), Hulst, A.G. (author), Touw, D. (author), Noort, D. (author), Vermeulen, N.P.E. (author), TNO Defensie en Veiligheid (author)

Covalent binding of reactive electrophilic intermediates to proteins is considered to play an important role in the processes leading to adverse drug reactions and idiosyncratic drug reactions. Consequently, both for the discovery and the development of new drugs, there is a great interest in sensitive methodologies that enable the detection of...

article 2007

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Human cytochrome P450 enzyme specificity for the bioactivation of estragole and related alkenylbenzenes

Jeurissen, S.M.F. (author), Punt, A. (author), Boersma, M.G. (author), Bogaards, J.J.P. (author), Fiamegos, Y.C. (author), Schilter, B. (author), van Bladeren, P.J. (author), Cnubben, N.H.P. (author), Rietjens, I.M.C.M. (author), TNO Kwaliteit van Leven (author)

Human cytochrome P450 enzymes involved in the bioactivation of estragole to its proximate carcinogen 1′-hydroxyestragole were identified and compared to the enzymes of importance for 1′-hydroxylation of the related alkenylbenzenes methyleugenol and safrole. Incubations with Supersomes revealed that all enzymes tested, except P450 2C8, are...

article 2007

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Human cytochrome P450 enzymes of importance for the bioactivation of methyleugenol to the proximate carcinogen 1′-hydroxymethyleugenol

Jeurissen, S.M.F. (author), Bogaards, J.J.P. (author), Boersma, M.G. (author), ter Horst, J.P.F. (author), Awad, H.M. (author), Fiamegos, Y.C. (author), van Beek, T.A. (author), Alink, G.M. (author), Sudhölter, E.J.R. (author), Cnubben, N.H.P. (author), Rietjens, I.M.C.M. (author), TNO Kwaliteit van Leven (author)

In vitro studies were performed to elucidate the human cytochrome P450 enzymes involved in the bioactivation of methyleugenol to its proximate carcinogen 1′-hydroxymethyleugenol. Incubations with Supersomes, expressing individual P450 enzymes to a high level, revealed that P450 1A2, 2A6, 2C9, 2C19, and 2D6 are intrinsically able to 1′...

article 2006

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The novel antifungal agent PLD-118 is neither metabolized by liver microsomes nor inhibits cytochrome P450 in vitro

Parnham, M.J. (author), Bogaards, J.J.P. (author), Schrander, F. (author), Schut, M.W. (author), Orešković, K. (author), Mildner, B. (author), TNO Kwaliteit van Leven (author)

PLD-118 is a novel, oral antifungal drug, under development for the treatment of Candida infections. Possible metabolism of PLD-118 by rat, dog and human S9 liver homogenates and inhibition of human cytochrome P450 (CYP) enzymes were investigated. PLD-118 (10 and 100 μm) incubated for 0-60 min with S9 fractions and NADPH was determined by HPLC,...

article 2005

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Identification of 14 quercetin phase II mono- and mixed conjugates and their formation by rat and human phase II in vitro model systems

van der Woude, H. (author), Boersma, M.G. (author), Vervoort, J. (author), Rietjens, I.M.C.M. (author), TNO Voeding (author)

In this study, the HPLC, UV-vis, LC-MS, and 1H NMR characteristics of 14 different phase II mono- and mixed conjugates of quercetin were determined, providing a useful tool in the identification of quercetin phase II metabolite patterns in various biological systems. Using these data, the phase II metabolism of quercetin by different rat and...

article 2004

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Acetoxy drug: Protein transacetylase of buffalo liver - Characterization and mass spectrometry of the acetylated protein product

Kohli, E. (author), Gaspari, M. (author), Raj, H.G. (author), Parmar, V.S. (author), Sharma, S.K. (author), van der Greef, J. (author), Kumari, R. (author), Gupta, G. (author), Khurana, P. (author), Tyagi, Y.K. (author), Watterson, A.C. (author), Olsen, C.E. (author), TNO Voeding (author)

The purification and characterization of the buffalo liver microsomal transacetylase (TAase) catalyzing the transfer of acetyl groups from a model acetoxy drug: 7,8-diacetoxy-4-methylcoumarin (DAMC) to GST3-3 has been described here. The enzyme was routinely assayed using DAMC and cytosolic GST as the substrates and was partially purified from...

article 2004

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Human cytochrome P450 enzyme specificity for bioactivation of safrole to the proximate carcinogen 1′-hydroxysafrole

Jeurissen, S.M.F. (author), Bogaards, J.J.P. (author), Awad, H.M. (author), Boersma, M.G. (author), Brand, W. (author), Fiamegos, Y.C. (author), van Beek, T.A. (author), Alink, G.M. (author), Sudhölter, E.J.R. (author), Cnubben, N.H.P. (author), Rietjens, I.M.C.M. (author), TNO Voeding (author)

In the present study, the cytochrome P450 mediated bioactivation of safrole to its proximate carcinogenic metabolite, 1′-hydroxysafrole, has been investigated for the purpose of identifying the human P450 enzymes involved. The 1′-hydroxylation of safrole was characterized in a variety of in vitro test systems, including Supersomes, expressing...

article 2004

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Prediction of interindividual variation in drug plasma levels in vivo from individual enzyme kinetic data and physiologically based pharmacokinetic modeling

Bogaards, J.J.P. (author), Hissink, E.M. (author), Briggs, M. (author), Weaver, R. (author), Jochemsen, R. (author), Jackson, P. (author), Bertrand, M. (author), van Bladeren, P. (author), Centraal Instituut voor Voedingsonderzoek TNO (author)

A strategy is presented to predict interindividual variation in drug plasma levels in vivo by the use of physiologically based pharmacokinetic modeling and human in vitro metabolic parameters, obtained through the combined use of microsomes containing single cytochrome P450 enzymes and a human liver microsome bank. The strategy, applied to the...

article 2000

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Differential maintenance of cytochrome P450 enzymes in cultured precision-cut human liver slices

Renwick, A.B. (author), Watts, P.S. (author), Edwards, R.J. (author), Barton, P.T. (author), Guyonnet, I. (author), Price, R.J. (author), Tredger, J.M. (author), Pelkonen, O. (author), Boobis, A.R. (author), Lake, B.G. (author), Centraal Instituut voor Voedingsonderzoek TNO TNO Voeding (author)

The maintenance of the major hepatic cytochrome P450 (CYP) enzymes has been studied in precision-cut human liver slices cultured for up to 72 h in supplemented RPMI 1640 medium. The relative apoprotein levels of 11 CYP enzymes were determined using a panel of antipeptide antibodes. In addition, 7-ethoxyresorufin O-deethylase, tolbutamide...

article 2000

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Comparison of three different in vitro mutation assays used for the investigation of cytochrome P450-mediated mutagenicity of nitro-polycyclic aromatic hydrocarbons

Kappers, W.A. (author), van Och, F.M.M. (author), de Groene, E.M. (author), Horbach, G.J. (author), Centraal Instituut voor Voedingsonderzoek TNO (author)

Three different in vitro mutation assays were used to investigate the involvement of cytochrome P450 enzymes in the activation of the nitro- polycyclic aromatic hydrocarbons (nitroPAHs) 1-nitropyrene and 2- nitrofluorene and their reduced metabolites amino-polycyclic aromatic hydrocarbons (aminoPAHs) 1-aminopyrene and 2-aminofluorene....

article 2000

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17α-Ethyl-5β-estrane-3α,17β-diol, a biological marker for the abuse of norethandrolone and ethylestrenol in slaughter cattle

van Puymbroeck, M. (author), Kuilman, M.E.M. (author), Maas, R.F.M. (author), Witkamp, R.F. (author), Leyssens, L. (author), van Miert, A.S.J.P.A.M. (author), Hendriks, L. (author), van der Zande, D.J.M. (author), Adriaensens, P. (author), Jacobs, M.-P. (author), Raus, J. (author), Centraal Instituut voor Voedingsonderzoek TNO (author)

The metabolism of the illegal growth promoter ethylestrenol (EES) was evaluated in bovine liver cells and subcellular fractions of bovine liver preparations. Incubations with bovine microsomal preparations revealed that EES is extensively biotransformed into norethandrolone (NE), another illegal growth promoter. Furthermore, incubations of...

article 1999

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Hydrogen atom abstraction of 3,5-disubstituted analogues of paracetamol by horseradish peroxidase and cytochrome P450

Bessems, J.G.M. (author), de Groot, M.J. (author), Baede, E.J. (author), te Koppele, J.M. (author), Vermeulen, N.P.E. (author), Centraal Instituut voor Voedingsonderzoek TNO (author)

1. The formation of free radicals during enzyme catalysed oxidation of eight 3,5-disubstituted analogues of paracetamol (PAR) has been studied. A simple peroxidase system as well as cytochrome P450-containing systems were used. Radicals were detected by electron spin resonance (ESR) on incubation of PAR and 3,5-diCH3-, 3,5-diC2H5-, 3,5-ditC4H9-,...

article 1998

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Identification of some important metabolites of boldenone in urine and feces of cattle by gas chromatography-mass spectrometry

Centraal Instituut voor Voedingsonderzoek TNO TNO Voeding (author), van Puymbroeck, M. (author), Kuilman, M.E.M. (author), Maas, R.F.M. (author), Witkamp, R.F. (author), Leyssens, L. (author), van der Zande, D.J.M. (author), Gelan, J. (author), Raus, J. (author)

17alpha-Boldenone (17alpha-BOL) and/or 17beta-boldenone (17beta-BOL) appear occasionally in fecal matter of cattle. In addition to 17alpha-BOL, a whole array of boldenone related substances can be found in the same samples. In vitro experiments with microsomal liver preparations and isolated hepatocytes combined with the excretion profiles found...

article 1998

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In vitro liver models are important tools to monitor the abuse of anabolic steroids in cattle

Centraal Instituut voor Voedingsonderzoek TNO TNO Voeding (author), van Puymbroeck, M. (author), Kuilman, M.E.M. (author), Maas, R.F.M. (author), Witkamp, R.F. (author), Leyssens, T. (author), van der Zande, D.J.M. (author), Gelan, J. (author), Raus, J. (author)

Current veterinary residue analysis mainly focuses on the monitoring of residues of the administered parent compound. However, it is possible that larger amounts of metabolites are excreted and that they can have a prolonged excretion period. In order to unravel specific metabolic steps and to identify possible biological markers, two in vitro...

article 1998

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The use of human in vitro metabolic parameters to explore the risk assessment of hazardous compounds: The case of ethylene dibromide

TNO Voeding Centraal Instituut voor Voedingsonderzoek TNO (author), Ploemen, J.P.H.T.M. (author), Wormhoudt, L.W. (author), Haenen, G.R.M.M. (author), Oudshoorn, M.J. (author), Commandeur, J.N.M. (author), Vermeulen, N.P.E. (author), de Waziers, I. (author), Beaune, P.H. (author), Watabe, T. (author), van Bladeren, P.J. (author)

Ethylene dibromide (1,2-dibromoethane, EDB) is metabolized by two routes: a conjugative route catalyzed by glutathione S-transferases (GST) and an oxidative route catalyzed by cytochrome P450 (P450). The GST route is associated with carcinogenicity. An approach is presented to use human purified GST and P450 enzymes to explore the importance of...

article 1997

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Species and strain differences in the hepatic cytochrome P450-mediated biotransformation of 1,4-dichlorobenzene

TNO Voeding Centraal Instituut voor Voedingsonderzoek TNO (author), Hissink, A.M. (author), Oudshoorn, M.J. (author), van Ommen, B. (author), van Bladeren, P.J. (author)

Our goal was to characterize possible species and strain differences in the hepatic microsomal biotransformation of 1,4-dichlorobenzene (1,4-DCB). Experiments compared extent of labeled 1,4-DCB conversion to oxidized metabolites, glutathione conjugates, and covalently bound metabolites by hepatic microsomes from humans, from male B6C3F1 mice,...

article 1997

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A physiologically based pharmacokinetic (PB-PK) model for 1,2-dichlorobenzene linked to two possible parameters of toxicity

TNO Voeding Centraal Instituut voor Voedingsonderzoek TNO (author), Hissink, A.M. (author), van Ommen, B. (author), Krüse, J. (author), van Bladeren, P.J. (author)

A physiologically based pharmacokinetic (PB-PK) model was developed for 1,2-dichlorobenzene (1,2-DCB) for the rat. This model was adjusted for the human situation, using human in vitro parameters, including a V(max) and K(m) determined with human microsomes. For comparison, the V(max) and K(m) values from the rat were scaled allometrically to...

article 1997

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Rat liver microsomal cytochrome P450-dependent oxidation of 3,5-disubstituted analogues of paracetamol

Bessems, J.G.M. (author), te Koppele, J.M. (author), van Dijk, P.A. (author), van Stee, L.L.P. (author), Commandeur, J.N.M. (author), Vermeulen, N.P.E. (author), Leiden/Amsterdam Ctr. for Drug Res., Division of Molecular Toxicology, Vrije Universiteit, De Boelelaan 1083, 1081 HV Amsterdam, Netherlands Dept. Vasc. Connective Tissue Res TNO Preventie en Gezondheid (author)

1. The cytochrome P450-dependent binding of paracetamol and a series of 3,5-disubstituted paracetamol analogues (R = -F, -Cl, -Br, -I, -C(H)3, -C2H5, -iC3H7) have been determined with β-naphthoflavone (βNF)-induced rat liver microsomes and produced reverse type I spectral changes. K(s,app) varied from 0.14 mM for 3,5-diiC3H7-paracetamol to 2.8...

article 1996