Orientador: Carmen Silvia Bertuzzo, Luis Alberto Magna / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Ciencias Medicas / Made available in DSpace on 2018-08-12T09:41:40Z (GMT). No. of bitstreams: 1 Rueda_LidianeCamila_M.pdf: 2492977 bytes, checksum: d9d2a855bfb9585fb574d275dcfe03a7 (MD5) Previous issue date: 2008 / Resumo: O câncer de mama (CM) é uma doença heterogênea e complexa, compreendendo múltiplas formas de apresentação clínica e morfológica, com diferentes graus de agressividade tumoral e potencial metastático. Acredita-se que 90% a 95% de todos os CM sejam esporádicos e decorram de mutações somáticas que se verificam durante a vida e que 5% a 10% sejam hereditários em virtude de uma mutação germinativa ao nascimento, que confere a estes indivíduos suscetibilidade ao CM. Entre os polimorfismos mais conhecidos de metabolização de drogas, estão os do sistema do citocromo P450. Os genes CYP1A1, CYP2D6 e CYP19 estão sendo estudados e em algumas populações mostraram uma associação positiva com a maior suscetibilidade ao CM. Este trabalho teve como objetivo investigar a presença dos polimorfismos T6235C (m1) e A4889G (m2) no gene CYP1A1, a presença dos polimorfismos A2637del (*3) e G1934A (*4) no gene CYP2D6 e a presença de alterações [TTTAn] no gene CYP19, por meio de um estudo de associação com uma amostra de 170 indivíduos, sendo 45 pacientes portadores de Adenocarcinoma e 120 controles normais. Foram utilizadas as técnicas extração de DNA, PCR e digestão enzimática. Não foi demonstrada, no presente estudo, associação entre os polimorfismos estudados e CM esporádico: (?2(2) = 1,12; p= 0,57) para o polimorfismo m1, (?2(2) = 0,83; p= 0,65) para o polimorfismo m2 do gene CYP1A1; (?2(2) = 0,15; p = 0,69) para o polimorfismo *3, (?2(2) = 2,41; p = 0,30) para o polimorfismo *4 do gene CYP2D6 e para as repetições em tandem [TTTA]n do gene CYP19. Os resultados sugerem que os polimorfismos gênicos estudados não estariam associados ao CM na amostra de indivíduos da região metropolitana de Campinas. Palavras-chave: CYP1A1, CYP2D6, CYP19, câncer de mama esporádico. / Abstract: Breast cancer (BC) is a complex disease, with heterogeneous clinical and morphologic presentation, that has with different degrees of tumoral aggressiveness and metastatic potential. It is known that 90% to 95% of all the BC are sporadical and happens because of somatic mutations that occurs during life and that 5% to 10% are hereditary because of germinate mutation due to births, which makes these individuals susceptibly to the BC. Among the best known polymorphism of metabolism of drugs, are the system cytochrome P450. The genes CYP1A1, CYP2D6 and CYP19 are being studied and in some populations because they had shown a positive association with the biggest susceptibility to the BC. This work had as objective to investigate the presence of polymorphisms T6235C (m1) and A4889G (m2) in gene CYP1A1, polymorphisms A2637del (*3) and G1934A (*4) in gene CYP2D6 and the presence of alterations [TTTAn] in gene CYP19, through a study of association with a sample of 170 individuals: 45 carrying patients of adenocarcinoma and 120 normal controls. The techniques had been used extraction of DNA, PCR and enzymatic digestion. It was not demonstrated, in this study the association between the polymorphisms studied and sporadic BC (?2(2) = 1,12; p= 0,57) for the polymorphism m1, (?2(2) = 0,83; p= 0,65) for the polymorphism m2 of gene CYP1A1; (?2(2) = 0,15; p= 0,69) for polymorphism *3, (?2(2) = 2,41; p= 0,30) for polymorphism *4 of gene CYP2D6 and for gene CYP19. The results suggest that the genic polymorphisms studied would not be associated with the BC in the sample of individuals in the metropolitan area of Campinas. key words: CYP1A1, CYP2D6, CYP19, sporadic breast cancer. / Mestrado / Mestre em Farmacologia

CYP2D6, a member of the cytochrome P450 enzyme system, has a central role in drug metabolism, it metabolizes 25 % of clinically used drugs. The gene that codes for the enzyme displays a high degree of polymorphism, which effects enzyme functions to various degrees. Aside from smaller mutations like SNPs, alleles may also feature duplications or deletion of the whole gene. Due to the clinical relevance of these mutations, a simple and precise method for genotyping is needed. In this study, a method based on pyrosequencing for copy number analysis was evaluated, wherein the copy number was determined by relative quantification to a reference gene CYP2D8P. During evaluation of the method, several adjustments were tried for optimization, including adjustments of annealing temperature and primer concentration. The results showed a difficulty in distinguishing between copy numbers using the method, as well as a high coefficient of variation. Therefore, further optimization is required before the method could be implemented into clinical practice.

M.Sc. / Plant cells have evolved the ability to detect pathogen ingress and subsequently activate defense-related functions as part of the plant pathogen response. One or more poorly defined signal transduction pathways, initiated upon recognition of the pathogen by the plant host, regulate expression of plant defense genes. Acquired resistance (AR) is an inducible defense mechanism exhibited by many plants that provides protection against a broad range of pathogens.Many chemical and environmental cues can elicit the same defenses or subsets therein. Cytochrome P450 enzymes are heme-dependent, mixed function oxidase systems that utilize dioxygen to produce a functionalized organic substrate and a molecule of water. They play important biosynthetic and detoxicative roles. They have been identified as being involved in the activation (e.g. allene oxide synthase) and execution of plant defense responses. To investigate the involvement of cytochromes P450 in the plant defense response - mainly through the activation of allene oxide synthases in the jamonate signaling pathway — Phaseolus vulgaris L.cv. Contender leaves were treated with chemical elicitors to mimic the plant-pathogen interaction and thereby activate plant defense responses. Through the use of differential display reverse transcription polymerase chain reaction and denaturing polyacrylamide gel electrophoresis, differentially expressed cDNA bands were isolated, cloned and sequenced. One of the cloned cDNA fragment proved to be a previously unreported cytochrome P450 cDNA, and was named CYP98A5. Dot blot analysis of bean leaves treated with various chemicals showed an enhanced expression of CYP98A5 in leaves treated with 3,5- dichlorosalicylic acid. Northern blot analysis of a time dependent induction study of CYP98A5 in bean leaves treated with this chemical compound indicated that 3,5-dichlorosalicylic acid induces CYP98A5 transcripts earlier than it is induced in control leaves. This might be indicative of a possible conditioning and sensitizing effect of 3,5- dichlorosalicylic acid on bean leaves to a more rapid and effective response with defense reactions once attacked by pathogens. CYP98A5, however, did not appear to be an allene oxide synthase when sequence comparison with other allene oxide synthases was performed; isolation and comparison of the complete CYP98A5 sequence could prove this wrong. It is not possible to assign any function to CYP98A5 at this stage; elucidation of the function of this enzyme in plants would provide more insight into this study.

Orientador: Stephen Hyslo / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Biologia / Made available in DSpace on 2018-08-07T09:47:37Z (GMT). No. of bitstreams: 1 Tarsitano_ChristianeAparecidaBadin_D.pdf: 24957423 bytes, checksum: 94d8809a19e27ce5d2957100482d3d27 (MD5) Previous issue date: 2006 / Resumo: óxido nítrico (NO), um co-produto do metabolismo do aminoácido Larginina para L-citrulina pela NO sintase (NOS), exerce importantes funções no controle do tôno vascular, no processo inflamatório, e na modulação da expressão gênica e atividade enzimática de diversas enzimas, tais como citocromos P-450 e NOS. A inibição crônica da biossíntese de NO por NW-nitro-L-argininemetil éster (L-NAME) leva à hipertensão e produz alterações morfológicas que incluem hipertrofia e remodelamento vascular, efeitos estes que são revertidos por inibidores da enzima conversora de angiotensina I (ECA) e antagonistas dos receptores AT1 de angiotensina 11. O NO exerce papel fundamental na hemodinâmica e função celular do fígado, e pode regular a atividade dos citocromos P450 monooxigenases que são importantes na biotransformação de substâncias endógenas e exógenas. Neste trabalho, examinamos a influência do tratamento com L-NAME sobre a morfologia hepática, o conteúdo de glicogênio, colesterole triglicérides,e a atividadee expressãodas isoformasCYP1A1/2, CYP 281/2, CYP2C11 e CYP2E1de citocromoP450.No tratamentoagudo estudamos também a expressão de duas metaloproteinases de matriz (MMP-2 e MPP-9). Ratos Wistar machos foram tratados com L-NAME (20 mg/rato/dia, administrado na água de beber) por quarto e oito dias (tratamento agudo) e duas, quatro e oito semanas (tratamento crônico) e os fígados foram removidos para análise. A indução enzimática foi realizada tratando-se os ratos com fenobarbital (para induzir CYP2B1/2), p-naphthoflavone (para induzir CYP1A1/2) (80 mg/kg/dia, Lp., 4 d) ou pirazole (200 mg/kg/dia, Lp., 2 d) (para induzir CYP2E1). O tratamento com L-NAME elevou significativamente a pressão sangüínea e esta foi revertida pelo tratamento concomitante com enalapril (25 mg/kg/dia, p.o., inibidor da ECA) ou losartan (30 mg/kg/dia, p.O.,antagonista dos receptores AT1). L-NAME causou hipertrofia vascular em artérias hepáticas, com depósito de colágeno perivascular e fibrose intersticial. Houve também um aumento significativo no conteúdo de glicogênio hepático. Todas estas alterações foram completamente revertidas por enalapril ou losartan. O tratamento com L-NAME não alterou o conteúdo de colesterol e triglicérides hepáticos, e não afetou as atividades basais e induzidas ou a expressão das isoformas de citocromo P450. O tratamento agudo com LNAME aumentou a expressão de MMP-2 e MMP-9 na parede vascular e em células inflamatórias (Ieucócitos, macrófagos). Esses resultados mostram que o tratamento agudo e crônico com L-NAME produz alterações morfológicas na vasculatura hepática e aumenta o conteúdo hepático de glicogênio, sem porém alterar o metabolismo de lípides ou a atividade e expressão de citocromos P450. A ausência de um efeito sobre os citocromos P450 indica que estas enzimas, não são influenciadas por níveis baixos de NO. Já a capacidade do enalapril e losartan em proteger contra as alterações morfológicas e o aumento de glicogênio indica um papel importante para o sistema renina-angiotensina nestas respostas / Abstract: Nitric oxide (NO), a co-product of the metabolism of L-arginine to L-citrulline by NO synthases (NOS), has an important role in regulating vascular tone, inflammatory responses, and the gene expression and enzymatic activity of various proteins, including cytochrome P450 and NOS. The chronic inhibition of NOS by Nffi-nitro-L-arginine methyl ester (L-NAME) produces sustained arterial hypertension and morphological alterations that include arterial wall hypertrophy and vascular remodeling. These changes can be prevented by concomitant treatment with angiotensin-converting enzyme (ACE) inhibitors and angiotensin 11 AT1 receptor antagonists. NO is an important modulator in the hepatic vasculature and of hepatic cell function, and may regulate the activity of cytochrome P450 monooxygenases involved in the biotransformation of endogenous and exogeous substances. In this work, we examined the influence of L-NAME on rat liver morphology, hepatic glycogen, cholesterol and triglyceride content, and the activities and expression of the cytochrome P450 isoforms CYP1A1/2, CYP2B1/2, CYP2C11 and CYP2E1. We also examined the expression of two matrix metalloproteinases (MMP-2 and MPP-9) after short-term treament with L-NAME. Male Wistar rats were treated with L-NAME (20 mg/ratlday, administered in the drinking water) for four and eight days (short-term treatment) and two, four and eight weeks (chronic treatment) and the livers were then removed for analysis. Enzymatic induction was produced by treating rats with phenobarbital (to induce CYP2B1/2), ~-naphthoflavone (to induce CYP1A1/2) (80 mg/kg/day each, i.p., 4 d) or pyrazole (200 mg/kg/day, i.p., 2 d) (to induce CYP2E1). Treatment with LNAME significantly elevated the blood pressure and this was reversed by concomitant treatment with enalapril (25 mg/kg/day, p.o., ACE inhibitor) or losartan (30 mg/kg/day, p.o., angiotensin II AT1 receptor antagonist). L-NAME caused vascular hypertrophy in hepatic arteries, with perivascular and interstitial fibrosis involving collagen deposition. There was also a significant increase in the hepatic glycogen content. Ali of these changes were completely reversed by concomitant treatment with enalapril or losartan. L-NAME had no effect on the hepatic cholesterol and triglyceride content, nor did it affect the basal or drug-induced activities and protein expression of the cytochrome P450 isoforms. Short-term treatment with L-NAME enhanced the expression of MMP-2 and MMP-9 in vessel walls and inflammatory cells (mast cells, macrophages). These results show that acute or chronic treatment with L-NAME produces morphological alterations in the hepatic vasculature and increases the hepatic glycogen content without affecting lipid metabolism or the activity or expression of cytochrome P450 isoforms. The lack of effect on cytochrome P450 activities and expression indicates that these enzymes are not significantly influenced by low levels of NO. In contrast, the ability of enalapril and losartan to prevent the morphological alterations and the increase in hepatic glycogen indicates an important role for the renin-antiogensin system in these responses / Doutorado / Histologia / Doutor em Biologia Celular e Estrutural

lsoflurane interacts with cytochrome P-450 in rat and human hepatic microsomes and the Δ6- and Δ5-desaturases in rat hepatic microsomes. The interaction of isoflurane with cytochrome P-450 results in its metabolism to fluoride ion and organofluorine metabolites. The cytochrome P-450 isozymes catalysing the defluorination of isoflurane were assessed in hepatic microsomes from phenobarbital-, β-naphthoflavone- and pregnenolone-16α-carbonitrilepretreated and untreated rats. One or more of the cytochrome P-450 isozymes induced by phenobarbital and pregnenolone-16α-carbonitrile appear to defluorinate isoflurane, but those induced by β-naphthoflavone do not. From a comparison of the extent of defluorination of isoflurane in hepatic microsomes from phenobarbital- and pregnenolone-16α-carbonitrile-pretreated rats, and their Kₘ and Vₘₐₓ values, it appears that isoflurane is defluorinated by one or more isozymes induced by both phenobarbital and pregnenolone-16α-carbonitrile. The major isozyme is probably cytochrome P-450PCN1. The metabolites of isoflurane were identified in human and phenobarbital-induced rat hepatic microsomes. In microsomes from phenobarbital-pretreated rats, isoflurane is metabolised to fluoride ion and trifluoroacetaldehyde; trifluoroacetic acid is not produced in measureable amounts. The trifluoroacetaldehyde produced binds to microsomal constituents. In human hepatic microsomes, the organofluorine metabolite is identified as trifluoroacetic acid. It is proposed that isoflurane is metabolised by different pathways in human and phenobarbital-induced rat hepatic microsomes. The interaction of isoflurane with the cyanide-sensitive factors was assessed by several criteria. Firstly, using the reoxidation of cytochrome b₅ as an index of fatty acid desaturase activity, isoflurane appears to interact with the Δ6- and/or Δ5-desaturases, but not the Δ9-desaturase. Secondly, these results were confirmed and clarified by the use of direct assays to measure the fatty acid desaturase activity. Using the direct assay, we confirmed that isoflurane did not inhibit the Δ9-desaturase and inhibited Δ6-desaturation of linoleic acid, but not the Δ6-desaturation of α-linolenic acid. The inhibition of the Δ6-desaturation of linoleic acid occurred at low millimolar concentrations of isoflurane. lsoflurane inhibits the Δ5-desaturation of eicosa-8, 11, 14-trienoic acid to a small extent which is only apparent at much higher concentrations of isoflurane than that which inhibits the Δ6-desaturase. Further studies focussed on measurement of the activity of Δ6-desaturase in order to attempt to study the kinetics of the inhibition of the Δ6-desaturase by isoflurane: Δ6-desaturase activity was assessed using hepatic microsomes as the source of the enzyme and linoleic acid as substrate precursor. In the course of these studies, we identified a number of factors that affected the apparent activity of the Δ6-desaturase in hepatic microsomes. These included significant levels of endogenous substrate and competing reactions in the hepatic microsomes. Endogenous substrate levels were quantified and corrected for. We then resorted to computer modelling to extract the kinetics of the Δ6-desaturase free of contributions from acyl-CoA synthetase and lysophospholipid acyltransferase, as well as enzyme decay. The kinetics of isoflurane inhibition of the Δ6-desaturase were then superimposed and studied by computer modelling.

Rheumatoid Arthritis is a chronic inflammatory systemic disease and is one of the autoimmune diseases. In this study, nine candidate genes of the cytochrome P450 system have been analyzed to determine their possible association with the formation of RA. These genes are: CYP1A1, CYP1B1, CYP2B6, CYP2E1, CYP2C9, CYP2D6, CYP2A6, CYP2C19 and CYP3A4.Within these genes, 21 single nucleotide polymorphism, SNPs, in 300 French Caucasian individuals (100 RA trio families) were genotyped using single-base-extensions, SBE, in a mass spectrometric analysis by MALDI-TOF-MS (matrix-assisted Laser Desorption/ Ionization-time-of-flight mass spectometry). The selection of the examined genes was carried out taking into account known associations with RA or other autoimmune disease, as well as known functional variants. Decisive were also the location of the gene and genetic variability. The results of genotyping were used to study polymorphisms on their association with Rheumatoid Arthritis. The statistical analyzes of CYP2C9 rs1799853 (3011) showed, in the family-based single-marker test, a lower transmission (TDT p-value 0.021) for the rare allele (3011-a). The case-control allelic based test shows, there is a protective effect (Odds Ratio 0.58). In the case-control-based genotypic test this issue could be reproduced (p-value 0.046). For the rare allele of the CYP2A6 rs1801272 (3022-a) the family-based single-marker test shows a lower transmittance (TDT p-value 0.037). The case-control allelic based test shows a protective effect of this allele (Odds Ratio 0.32). In the case-control-based genotypic test a statistical trend to protective behavior of this allele occurs. SNPs with predicted functional relevance showed no statistical abnormalities in the studied cohort. In genome-wide studies, the results could not be tracked, at least at the gene level weak associations could be detected. The results of this study should be to replicate in one second independent cohort. Care should be taken specifically to xenobiotic stress, such as job stress, smoking, and medication. In subsequent studies more SNPs of the candidate genes could also genotyped in order to verify the genetic variability with reference to of the haplotypes in more detail. Should the above-mentioned associations be confirmed, functional studies on different gene expression or altered metabolite spectrum are highly interesting.

Indiana University-Purdue University Indianapolis (IUPUI) / Cytochrome P450 2D6 (CYP2D6) is an important drug metabolizing enzyme that is involved in the metabolism of 20-25% of commonly prescribed drugs. There is interindividual variability in CYP2D6 enzyme activity and this leads to compromised metabolism of many drugs. Genetic and environmental factors explain only a part of the interindividual variability; the other factors that contribute to this variability are largely unknown. Hence, it becomes important to study CYP2D6 to understand the endogenous and exogenous factors that control its activity. The specific objective of this research was to determine the contribution of genetic and epigenetic factors in the regulation of CYP2D6 expression and activity. The specific aims were: (1) to identify the common CYP2D6 polymorphisms in Vietnamese and Filipino women with breast cancer and evaluate its association with plasma concentrations of endoxifen (an active metabolite of the breast cancer therapeutic drug, tamoxifen); (2) to identify the CYP2D6 copy number variations (CNVs) in these women and evaluate their association with endoxifen concentration; and (3) to identify microRNAs (miRNAs) that regulate the expression of CYP2D6 directly or indirectly. The results of this study indicated that: (1) in Vietnamese and Filipino women, the reduced function allele CYP2D6*10 was frequent (~55%) and it was significantly associated with reduced endoxifen concentration; (2) in these women, only 39% carried two copies of the CYP2D6 gene, the rest had a genomic imbalance for CYP2D6, primarily involving the CYP2D6(*36)n-*10 allele. However, carrying multiple copies of CYP2D6*36 allele did not significantly affect CYP2D6 activity, suggesting that multiple copies of a gene does not always translate to additive effects; and (3) microRNAs were identified to target HNF4A, a transcriptional factor that regulates CYP2D6 expression. These miRNAs are likely to play an important role in the indirect regulation of CYP2D6. Taken together, these results emphasize on the role of polymorphisms, CNVs and possibly miRNAs in the regulation of CYP2D6. These clinically important biomarkers will help to improve the efficacy and reduce the side effects of many CYP2D6 substrate drugs and thus contribute to personalization of drug therapy.

Les gènes de la sous-famille CYP2B sont fortement activés par des traitements au phénobarbital ou des inducteurs de type phénobarbital, et cette réponse nécessite la présence du constitutive androstane receptor (CAR). La dexaméthasone, un glucocorticoïde synthétique, a la capacité d' induire CYP2Bl et CYP2B2 chez le rat et CYP2B lOchez la souris. Les travaux présentés dans ce mémoire démontrent le rôle majeur du récepteur des glucocorticoïdes (GR) dans la réponse à la dexaméthasone, ce qui constitue une nouvelle voie de régulation des gènes CYP2B. De plus, cinq régions critiques impliquées dans la réponse ont été caractérisées et elles formeraient les éléments clé d'une unité de réponse aux glucocorticoïdes de CYP2B2. Pour la première fois, CAR peut jouer le rôle de facteur accessoire, en stimulant la réponse à la dexaméthasone passant par GR. En conclusion, les résultats présentés ici décrivent une nouvelle voie de régulation des gènes CYP2B de rongeurs.

Les gènes de rat CYP2B1 et CYP2B2 ainsi que leur orthologue Cyp2b10 chez la souris sont induits dans le foie par le phénobarbital, un barbiturique, et par les glucocorticoïdes comme la dexaméthasone. Les médiateurs de ces réponses sont respectivement le récepteur constitutif des androstanes (CAR) et le récepteur des glucocorticoïdes. Dans ce mémoire, il est entrepris de vérifier si CAR joue également un rôle dans la réponse des CYP2B aux glucocorticoïdes in vivo et si les xénobiotiques inducteurs influencent la localisation des protéines CYP2B microsomales, aux mitochondries. De plus, l’analyse de sites d’hypersensibilité à la DNase I dans les introns du gène Cyp2b10, conservés dans le gène CYP2B1 a mené à la détermination, entre autres, d’une séquence de 100 paires de bases possédant une activité promotrice constitutive pouvant générer un transcrit de 3 500 paires de bases.

Chaque année, les compagnies novatrices mettent sur le marché des nouvelles molécules à visée thérapeutique, pour le bien-être de tous. Dans le développement de ces nouveaux médicaments, les études de métabolisme et l'évaluation des interactions médicamenteuses potentielles constituent une étape essentielle et requise pour l'approbation réglementaire. L'approche expérimentale est basée sur l'utilisation des modèles animaux et les données recueillies servent à la prédiction de la cinétique et de la toxicité chez l'humain. Plusieurs espèces, incluant la souris, le rat, le chien, le lapin, le porc et le singe, sont ainsi utilisées. Cependant, cette approche souffre de quelques limites, en particulier des différences inter-espèces au niveau des enzymes impliqués dans la biotransformation des médicaments chez l'humain, dont les cytochromes P450. De ce fait, il n'est pas rare d'utiliser plusieurs modèles animaux pour prédire la cinétique et la toxicité chez l'homme. Le cobaye (cavia porcellus), qui présente plusieurs avantages au niveau de sa physiologie, pourrait ainsi constituer un modèle animal de plus pour ces études. L'objectif de cette étude est donc de caractériser la sous-famille des cytochromes P450 2C, le transporteur membranaire MDRl/P-gp ainsi que les récepteurs nucléaires PXR et CAR chez le cobaye. Cette étude s'inscrit dans un effort de fournir des données fondamentales afin de supporter l'utilisation de cet animal comme modèle de métabolisme des médicaments. Pour ce faire, les séquences des gènes codant pour ces protéines ont été déterminées par des techniques de biologie moléculaire. L'immunobuvardage de type Western a permis de démontrer l'expression des protéines CYP2C, P-gp/MDRl et PXR. Des études fonctionnelles pour le CYP2C ont été réalisées par l'incubation de microsomes hépatiques de cobaye avec le diclofenac et le tolbutamide, deux substrats du CYP2C9 chez l'homme, en présence des inhibiteurs spécifiques au CYP2C9 ; le sulfaphénazole, l'acide tiénilique et le fluconazole, et au CYP3A4; le kétoconazole. Ces études ont démontré la formation de 4'-hydroxydiclofénac et de 4'-hydroxytolbutamide, deux metabolites du CYP2C9, et l'inhibition de ces réactions par l'acide tiénilique seulement. Des études fonctionnelles de P-gp/MDRl ont été réalisées avec l'essai d'accumulation de calcéine-AM dans des cellules HEK293 transfectées avec le gène ABCB1/MDR1 de cobaye. Elles ont démontré une activité de transport à l'égard de ce substrat, et une inhibition par le verapamil, un inhibiteur de la P-gp. Les études de distribution de la P-gp/MDRl, par les techniques de PCR et d'immunobuvardage de type Western, ont démontré l'expression de cette protéine dans l'intestin, le foie, le poumon, le ventricule, l'oreillette, le cervelet, le lobe du cerveau et la glande surrénale du cobaye. Bref, ces résultats montrent que le cobaye exprime un enzyme fonctionnel de la sous-famille des cytochromes P450 2C, le transporteur membranaire P-gp/MDRl fonctionnel et les récepteurs nucléaires PXR et CAR. En se basant sur ces résultats et considérant l'importance de ces protéines dans la biotransformation des médicaments, il est raisonnable de postuler que cela renforce la pertinence d'utiliser cet animal comme modèle dans de telles études.