• Toxicological Research
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• 제18권4호
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• pp.331-339
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• 2002

Phenoxy compounds, 2,4-Dichlorophenol acetoxy acid (2,4-D) and 2,4-dichlorophenol (DCP), are widely used as a hormonal herbicide and intermediate for pesticide manufacturing, respectively. In order to assess the potential of these compounds as endocrine disruptors, we studied the androgenicity of them wing in vivo and in vitro androgenicity assay system. Administration of 2,4-D (50 mg/kg/day, p.o.) or DCP (100 mg/kg/day, p.o.) to rats caused an increase in the tissue weight of ventral prostate, Cowpers gland and glands penis. These increase of androgen-dependent tissues were additively potentiated when rats were simultaneously treated with low dose of testosterone (1 g/kg, s.c.). 2,4-D increased about 350% of the luciferase activity in the PC cells transiently cotransfected phAR and pMMTV-Luc at concentration of $10^{-9}$ M. In 2,4-D or DCP-treated castrated rats, testosterone 6$\beta$-hydroxylase activity was not significantly modulated even when rats were co-treated with testosterone. In vitro incubation of 2,4-D and DCP with microsomes at 50 $\mu$M inhibited testosterone 6$\beta$-hydroxylase activity about 27% and 66% in rat liver microsomes, about 44% and 54% in human liver microsomes and about 50% and 45% in recombinant CYP3A4 system, respectively. The amounts of total testosterone metabolites were reduced about 33% and 75% in rat liver microsomes, 69% and 73% in human liver microsomes and 54% and 64% in recombinant CYP3A4 by 2,4-D or DCP, respectively. Therefore, the additive androgenic effect of 2,4-D or DCP by the co-administration of the low dose of testosterone may be due to the increased plasma level of testosterone by inhibiting the cytochrome P450-mediated metabolism of testosterone. These results collectively suggested that 2,4-D and DCP may act as androgenic endocrine disrupter by binding to the androgen receptor as well as by inhibiting the metabolism of testosterone.

• Toxicological Research
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• 제24권3호
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• pp.195-199
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• 2008

It has been reported that hepatic microsomal cytochrome P450(CYP) 2E1 is responsible for the metabolism of chlorzoxazone(CZX) to 6-hydroxychlorzoxazone. The present study was undertaken to assess the possible interaction of rutaecarpine, an alkaloid originally isolated from the unripe fruit of Evodia rutaecarpa, with CZX. Male Spraque-Dawley rats were administered with 80 mg/kg/day of oral rutaecarpine for three consecutive days. Twenty four hr after the pre-treatment with rutaecarpine, the rats were treated with 20 mg/kg of intravenous CZX. Rat hepatic microsomes isolated from rutaecarpine-treated rats showed greater(50% increase) activity of p-nitrophenol hydroxylase(a marker of CYP2E1) when compared with the control rats. Compared with control rats, the AUC of CZX was significantly smaller(84% decrease) possibly due to significantly faster CL(646% increase) in rats pretreated with rutaecarpine. This could be, at least partially, due to induction of CYP2E1 by rutaecarpine.

• 한국임상약학회지
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• 제23권3호
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• pp.206-212
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• 2013

Purpose: The aim of this study was to investigate the effect of nimodipine on the pharmacokinetics of warfarin after oral and intravenous administration of warfarin in rats. Methods: Warfarin was administered orally (0.2 mg/kg) or intravenously (0.05 mg/kg) without or with oral administration of nimodipine (0.5 or 2 mg/kg) in rats. The effect of nimodipine on the P-glycoprotein as well as cytochrome P450 (CYP) 3A4 activity was also evaluated. Results: Nimodipine inhibited CYP3A4 enzyme activity with 50% inhibition concentration ($IC_{50}$) of $10.2{\mu}M$. Compared to those animals in the oral control group (warfarin without nimodipine), the area under the plasma concentration-time curve (AUC) of warfarin was significantly greater (0.5 mg/kg, P<0.05; 2 mg/kg, P<0.01) by 31.3-57.6%, and the peak plasma concentration ($C_{max}$) was significantly higher (2 mg/kg, P<0.05) by 29.4% after oral administration of warfarin with nimodipine, respectively. Consequently, the relative bioavailability of warfarin increased by 1.31- to 1.58-fold and the absolute bioavailability of warfarin with nimodipine was significantly greater by 64.1-76.9% compared to that in the control group (48.7%). In contrast, nimodipine had no effect on any pharmacokinetic parameters of warfarin given intravenously. Conclusion: Therefore, the enhanced oral bioavailability of warfarin may be due to inhibition of CYP 3A4-mediated metabolism rather than P-glycoprotein-mediated efflux by nimodipine.

• Asian Pacific Journal of Cancer Prevention
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• 제16권12호
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• pp.4927-4935
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• 2015

Northeastern India is a major nasopharyngeal carcinoma (NPC) high risk-area although the rest of the country has very low incidence. A case-control study of 105 NPC cases and 115 controls was conducted to identify the potential risk factors for NPC development in this region. Information was collected by interviewer about socio-demographic characteristics, cigarette smoking, alcohol consumption, dietary history, occupational history, and a family history of cancer. Epstein-Barr viral load was assayed from the blood DNA by real time PCR. Associations between GSTs genotypes, cytochrome P450 family including CYP1A1, CYP2E1 and CYP2A6 polymorphisms and susceptibility to relationship between the diseases were studied using PCR-RFLP assay. Results indicate that Epstein-Barr virus load was significantly higher in patients compared to controls (p<0.0001). Furthermore, concentration of blood EBV-DNA was significantly higher in advanced stage disease (Stage III and IV) than in early stage disease (Stage I and II) (p<0.05). Presence of CYP2A6 variants that reduced the enzyme activity was significantly less frequent in cases than controls. Smoked meat consumption, exposure to smoke, living in poorly ventilated house and alcohol consumption were associated with NPC development among the population of Northeastern India. Thus, overall our study revealed that EBV viral load and genetic polymorphism of CYP2A6 along with living practices which include smoked meat consumption, exposure to smoke, living in poorly ventilated houses and alcohol consumption are the potential risk factors of NPC in north eastern region of India. Understanding of the risk factors and their role in the etiology of NPC are helpful forpreventive measures and screening.

• 한국독성학회:학술대회논문집
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• 한국독성학회 2001년도 International Symposium on Signal transduction in Toxicology
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• pp.149-149
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• 2001

Cytochrome P450 (CYP) 2D6 and CYP3A4 have been reported to be involved in the major metabolic pathways and formations of neurotoxic metabolites (HPP$\^$+/, RHPP$\^$+/) from haloperidol (HAL). However, no in vivo study has been addressed to the involvement of both CYP isoforms on the formation of toxic HAL metabolites.(omitted)

• Toxicological Research
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• 제13권1_2호
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• pp.117-125
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• 1997

In order to assess the possibility whether CYP2D is involved in caffeine metabolism, we have purified and characterized the rat liver microsomal cytochrome P4502D1 (CYP2D1), equivalent to CYP2D6 in human liver, and have utilized the reconstituted CYP2D1 in the metabolism of 4 primary caffeine (1, 3, 7-trimethylxanthine) metabolites such as paraxanthine (1, 7-dimethylxanthine), 1, 3, 7-trimethylurate, theophylline (1, 3-dimethylxanthine) and theobromine (3, 7-dimethylxanthine). Rat liver CYP 2D1 has been purified to a specific content of 8.98 nmole/mg protein (13.4fold purification, 1.5% yield) using $\omega$-aminooctylagarose, hydroxlapatite, and DE52 columns in a sequential manner. As judged from sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), the purified CYP2D1 was apparently homogeneous. Molecular weight of the purified CYP2D1 was found to be 51, 000 Da. Catalytic activity of the purified and then reconstituted CYP2D1 was confirmed by using bufuralol, a known subsFate of CYP2D1. The reconstituted CYP2D1 was found to produce to 1-hydroxylbufuralol at a rate of 1.43$\pm$0.13 nmol/min/nmol P450. The kinetic analysis of bufuralol hydroxylation indicated that Km and Vmax values were 7.32$\mu M$ and 1.64 nmol/min/nmol P450, respectively. The reconstituted CYP2D1 could catalyze the 7-demethylation of PX to 1-methylxanthine at a rate of 12.5 pmol/min/pmol, and also the 7- and 3- demethylations of 1, 3, 7-trimethylurate to 1, 3-dimethylurate and 1, 7-dimethylurate at 6.5 and 12.8 pmol/min/pmol CYP2D1, respectively. The reconstituted CYP2D1 could also 3-demethylate theophylline to 1-methylxanthine at 5 pmol/min/pmol and hydroxylate the theophylline to 1, 3-dimethylurate at 21.8 pmol/min/pmol CYP2D1. The reconstituted CYP2D1, however, did not metabolize TB at all (detection limits were 0.03 pmol/min/pmol). This study indicated that CYP2D1 is involved in 3-and 7-demethylations of paraxanthine and theophylline and suggested that CYP2D6 (equivalent to CYP2D1 in rat liver) present in human liver may be involved in the secondary metabolism of the primary metabolites of caffeine.

• Archives of Pharmacal Research
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• 제27권5호
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• pp.547-553
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• 2004

The pyrrolizidine alkaloids (PAs), contained in a number of traditional remedies in Africa and Asia, show wide variations in metabolism between animal species but little work has been done to investigate differences between animal strains. The metabolism of the PA senecionine (SN) in Fischer 344 (F344) rats has been studied in order to compare to that found in the previously investigated Sprague-Dawley (SO) rats (Drug Metab. Dispos. 17: 387, 1989). There was no difference in the formation of ($\pm$) 6,7-dihydro-7-hydroxy-1-hydroxymethyl-5H-pyrrolizine (DHP, bioactivation) by hepatic microsomes from either sex of SO and F344 rats. However, hepatic microsomes from male and female F344 rats had greater activity in the Noxidation (detoxication) of SN by 88% and 180%, respectively, when compared to that of male and female SD rats. Experiments conducted at various pH showed an optimum pH of 8.5, the optimal pH for flavin-containing monooxygenase (FMO), for SN N-oxidation by hepatic microsomes from F344 females. In F344 males, however, a bimodal pattern was obtained with activity peaks at pH 7.6 and 8.5 reflecting the possible involvement of both cytochrome P450 (CYP) and FMO. Use of specific inhibitors (SKF525A, 1-benzylimidazole and methimazole) showed that the N-oxide of SN was primarily produced by FMO in both sexes of F344 rats. In contrast, SN N-oxide formation is known to be catalyzed mainly by CYP2C11 rather than FMO in SD rats. This study, therefore, demonstrated that there were substantial differences in the formation of SN N-oxide by hepatic microsomes from F344 and SD rats and that this detoxification is catalyzed primarily by two different enzymes in the two rat strains. These findings suggest that significant variations in PA biotransformation can exist between different animal strains.

• Translational and Clinical Pharmacology
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• 제25권3호
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• pp.147-152
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• 2017

This study focused on the role of cytochrome P450 2D6 (CYP2D6) genotypes to predict phenotypes in the metabolism of dextromethorphan. CYP2D6 genotypes and metabolic ratios (MRs) of dextromethorphan were determined in 201 Koreans. Unsupervised clustering algorithms, hierarchical and k-means clustering analysis, and color visualizations of CYP2D6 activity were performed on a subset of 130 subjects. A total of 23 different genotypes were identified, five of which were observed in one subject. Phenotype classifications were based on the means, medians, and standard deviations of the log MR values for each genotype. Color visualization was used to display the mean and median of each genotype as different color intensities. Cutoff values were determined using receiver operating characteristic curves from the k-means analysis, and the data were validated in the remaining subset of 71 subjects. Using the two highest silhouette values, the selected numbers of clusters were three (the best) and four. The findings from the two clustering algorithms were similar to those of other studies, classifying $^*5/^*5$ as a lowest activity group and genotypes containing duplicated alleles (i.e., $CYP2D6^*1/^*2N$) as a highest activity group. The validation of the k-means clustering results with data from the 71 subjects revealed relatively high concordance rates: 92.8% and 73.9% in three and four clusters, respectively. Additionally, color visualization allowed for rapid interpretation of results. Although the clustering approach to predict CYP2D6 phenotype from CYP2D6 genotype is not fully complete, it provides general information about the genotype to phenotype relationship, including rare genotypes with only one subject.

• 생물정신의학
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• 제18권3호
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• pp.159-162
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• 2011

Venlafaxine is among the most widely prescribed antidepressants. It is extensively metabolized to O-desmethylvenlafaxine via cytochrome P450 (CYP) 2D6. We report a case of acute toxic hepatitis resulting from venlafaxine in a 54-year-old woman with pain disorder. During venlafaxine treatment, laboratory tests revealed elevated liver enzymes with a maximum of 169 IU/L for aspartate transaminase (AST) and 166 IU/L for alanine transaminase (ALT). AST and ALT levels returned to normal after 6 days of discontinuation of venlafaxine. The patient was finally diagnosed with acute toxic hepatitis through liver biopsy. This case indicates the importance that clinicians should be aware of the hepatotoxicity of venlafaxine in practice.

• Toxicological Research
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• 제20권3호
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• pp.195-203
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• 2004

4-Tert-Octylphenol (OP) is a surfactant additive widely used in the manufacture of a variety of detergents and plastic products. OP can disrupt endocrine function in humans and animals. This study was carried out to obtain toxicokinetic parameters of OP in male Sprague-Dawley (SD) rats. Male rats were administered with OP by single oral application of 200 mg/kg body weight. Blood, urine and tissues samples were taken at several time intervals after administration. Analysis of samples for OP was performed by column-switching high performance liquid chromatography (HPLC). In addition, we exam-ined tissue distribution and accumulation of OP after single oral application of 50, 100, and 200 mg/kg, single intravenous injection of 1, 5 and 10 mg/kg or daily application of 50 mg/kg for 14 consecutive days. After single oral administration of 200 mg/kg, Cmax of 213 $\pm$ 123 ng/ml was reached within the first 1.3 hr (Tmax) in the plasma. AUC was calculated for 1,333$\pm$484 ngㆍhr/ml. The final elimination half-life of plasma was longer than that of urine, but urinary clearance was lower than oral. A very small fraction of OP (Fe < 0.0017%) was excreted in urine within 24 hr. These results indicated that the major excretion route of OP was not urine. The mean maximal tissue distribution of OP was obserbed at 6 hr after treatment and slowly decreased time-dependently. High OP concentrations were detected in fat at 24 hr. The OP in fat was slowly released with longer elimination half-life and lower clearance than that of other tissues. OP was not accumulated in the liver following single oral application but 14-day oral treatments resulted in two-fold accumulation. It was probably due to the saturation of detoxification pathways. On the other hand, the mRNA expression of cytochrome P450 isoforms except CYP2C11 was not affected by OP at any dose. The expression of CYP2C11 mRNA decreased in a dose-dependent manner. This result suggests that OP changes expression of the male-specific cytochrome P450 isoforms in rat liver, and these changes are closely related to the toxic and estrogenic effect of OP.