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Effects of cytochrome P450 inhibitors on the biotransformation of fluorogenic substrates by adult male rat liver microsomes and cDNA-expressed rat cytochrome P450 isoforms.
Toxicol Sci. 2010 Feb; 113(2):293-304.TS

Abstract

We have evaluated the use of a panel of six fluorogenic cytochrome P450 (CYP) substrates as a potential tool for rapid screening for global changes in CYP activity in rats under different physiological conditions. The biotransformation of 3-[2-(N,N-diethyl-N-methylammonium)ethyl]-7-methoxy-4-methylcoumarin (AMMC), 7-benzyloxy-4-(trifluoromethyl)-coumarin, 7-benzyloxyquinoline, 3-cyano-7-ethoxycoumarin, 7-methoxy-4-(trifluoromethyl)-coumarin, and 7-ethoxy-4-trifluoromethyl-coumarin by microsomes from adult male rat liver were characterized, their sensitivities to 15 putative inhibitors were determined and compared to similar experiments using nine different complementary DNA (cDNA)-expressed rat CYPs. Inhibitory profiles of the substrates in microsomes were different from each other, with some overlap, suggesting that each substrate is to some extent biotransformed by a different CYP isoform. Ketoconazole and clotrimazole were nonselective inhibitors, while ticlopidine selectively inhibited biotransformation of AMMC. CYP2A1 did not biotransform any of the substrates, and CYP2E1 was insensitive to all the inhibitors tested. Some inhibitors did not affect the biotransformation of the fluorogenic substrates by cDNA-expressed isoforms as predicted by their effects on conventional substrates, e.g., chlorzoxazone and diethyldithiocarbamate were inactive against CYP2E1, and CYP2C6 was not inhibited by sulfaphenazole. When results in microsomes and cDNA-expressed CYPs were compared, only the majority of the biotransformation of AMMC by microsomes could be assigned with full confidence to a specific CYP isoform, namely CYP2D2. Nevertheless, different inhibitory profiles of the substrates indicate that the panel will be useful for rapid functional quantification of global CYP activity in rats under different experimental conditions. Our results also demonstrate the inappropriateness of extrapolating inhibitory data between conventional and fluorogenic CYP substrates.

Authors+Show Affiliations

Department of Obstetrics & Gynecology, McMaster University, Ontario, Canada.No affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info available

Pub Type(s)

Journal Article
Research Support, Non-U.S. Gov't

Language

eng

PubMed ID

19858067

Citation

Makaji, Emilija, et al. "Effects of Cytochrome P450 Inhibitors On the Biotransformation of Fluorogenic Substrates By Adult Male Rat Liver Microsomes and cDNA-expressed Rat Cytochrome P450 Isoforms." Toxicological Sciences : an Official Journal of the Society of Toxicology, vol. 113, no. 2, 2010, pp. 293-304.
Makaji E, Trambitas CS, Shen P, et al. Effects of cytochrome P450 inhibitors on the biotransformation of fluorogenic substrates by adult male rat liver microsomes and cDNA-expressed rat cytochrome P450 isoforms. Toxicol Sci. 2010;113(2):293-304.
Makaji, E., Trambitas, C. S., Shen, P., Holloway, A. C., & Crankshaw, D. J. (2010). Effects of cytochrome P450 inhibitors on the biotransformation of fluorogenic substrates by adult male rat liver microsomes and cDNA-expressed rat cytochrome P450 isoforms. Toxicological Sciences : an Official Journal of the Society of Toxicology, 113(2), 293-304. https://doi.org/10.1093/toxsci/kfp255
Makaji E, et al. Effects of Cytochrome P450 Inhibitors On the Biotransformation of Fluorogenic Substrates By Adult Male Rat Liver Microsomes and cDNA-expressed Rat Cytochrome P450 Isoforms. Toxicol Sci. 2010;113(2):293-304. PubMed PMID: 19858067.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Effects of cytochrome P450 inhibitors on the biotransformation of fluorogenic substrates by adult male rat liver microsomes and cDNA-expressed rat cytochrome P450 isoforms. AU - Makaji,Emilija, AU - Trambitas,Cristina S, AU - Shen,Pamela, AU - Holloway,Alison C, AU - Crankshaw,Denis J, Y1 - 2009/10/25/ PY - 2009/10/28/entrez PY - 2009/10/28/pubmed PY - 2010/2/23/medline SP - 293 EP - 304 JF - Toxicological sciences : an official journal of the Society of Toxicology JO - Toxicol Sci VL - 113 IS - 2 N2 - We have evaluated the use of a panel of six fluorogenic cytochrome P450 (CYP) substrates as a potential tool for rapid screening for global changes in CYP activity in rats under different physiological conditions. The biotransformation of 3-[2-(N,N-diethyl-N-methylammonium)ethyl]-7-methoxy-4-methylcoumarin (AMMC), 7-benzyloxy-4-(trifluoromethyl)-coumarin, 7-benzyloxyquinoline, 3-cyano-7-ethoxycoumarin, 7-methoxy-4-(trifluoromethyl)-coumarin, and 7-ethoxy-4-trifluoromethyl-coumarin by microsomes from adult male rat liver were characterized, their sensitivities to 15 putative inhibitors were determined and compared to similar experiments using nine different complementary DNA (cDNA)-expressed rat CYPs. Inhibitory profiles of the substrates in microsomes were different from each other, with some overlap, suggesting that each substrate is to some extent biotransformed by a different CYP isoform. Ketoconazole and clotrimazole were nonselective inhibitors, while ticlopidine selectively inhibited biotransformation of AMMC. CYP2A1 did not biotransform any of the substrates, and CYP2E1 was insensitive to all the inhibitors tested. Some inhibitors did not affect the biotransformation of the fluorogenic substrates by cDNA-expressed isoforms as predicted by their effects on conventional substrates, e.g., chlorzoxazone and diethyldithiocarbamate were inactive against CYP2E1, and CYP2C6 was not inhibited by sulfaphenazole. When results in microsomes and cDNA-expressed CYPs were compared, only the majority of the biotransformation of AMMC by microsomes could be assigned with full confidence to a specific CYP isoform, namely CYP2D2. Nevertheless, different inhibitory profiles of the substrates indicate that the panel will be useful for rapid functional quantification of global CYP activity in rats under different experimental conditions. Our results also demonstrate the inappropriateness of extrapolating inhibitory data between conventional and fluorogenic CYP substrates. SN - 1096-0929 UR - https://www.unboundmedicine.com/medline/citation/19858067/Effects_of_cytochrome_P450_inhibitors_on_the_biotransformation_of_fluorogenic_substrates_by_adult_male_rat_liver_microsomes_and_cDNA_expressed_rat_cytochrome_P450_isoforms_ L2 - https://academic.oup.com/toxsci/article-lookup/doi/10.1093/toxsci/kfp255 DB - PRIME DP - Unbound Medicine ER -