• Proceedings of the Korea Society of Environmental Toocicology Conference
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• 2001.05a
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• pp.124-124
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• 2001

Microsomes isolated from Spodoptera frugiperda (Sf)9 cells infected wi th human FM01 recombinant baculovirus catalyzed the NADPH- and 02-dependent oxidation of methimazole, thiourea, and phenylthiourea. However there was no detectable activity with 1,3-diphenylthiourea or larger thiocarbamides. Microsomes from control Sf9 cells were devoid of methimazole or thiourea S-oxygenase activity. (omitted)

• Archives of Pharmacal Research
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• v.21 no.6
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• pp.677-682
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• 1998

The present study was designed to examine the metabolism of 1-anilino-8-naphthalene sulfonate (ANS), an anionic compound which is transported into liver via "multispecific organ ic anion transporter", with rat hepatic microsomes. TLC analysis indicated that the fluorescent metabolites were not produced to a measurable extent, which made it possible to assess the ANS metabolism by measuring the fluorescence disappearance. The metabolism of ANS was remarkably inhibited by the presence of SKF-525A as well as by the substitution of 02 by CO gas. ANS metabolism by microsomes also required NADPH as a cofactor. These results indicated that the microsomal monooxygenase system might be mainly responsible for the ANS metabolism. The maximum velocity ($V_{max}$) and Michaelis constant ($K_m$) were calculated to be $4.3{\pm}0.2$ nmol/min/mg protein and $42.1{\pm}2.0\;{\mu}M$, respectively. Assuming that 1g of liver contains 32mg of microsomal protein, the $V_{max}$ value was extrapolated to that per g of liver ($V_{max}^I$). The intrinsic metabolic clearance ($CL_{int}$) under linear conditions calculated from this in vitro metabolic study was 3.3ml/min/g liver, being comparable with that (3.0ml/min/g liver) calculated by analyzing the in vivo plasma disappearance curve in a previous study. Furthermore, the effects of other organic anions on the metabolism of ANS were examined. Bromophenolblue (BPB) and rose bengal (RB) competitively inhibited the metabolism of ANS, while BSP inhibited it only slightly. The inhibition constant ($K_i$) of BPB ($6\;{\mu}M$) was much smaller than that of RB ($200\;{\mu}M$). In conclusion, the microsomal monooxygenase system plays a major role in the metabolism of ANS, and other unmetabolizable organic anions (BPB and RB) compete for this metabolism.

• The Journal of Internal Korean Medicine
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• v.29 no.4
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• pp.846-855
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• 2008

Objects : The aim of this study was to investigate the influence of five herbal medicines on cytochrome P450 3A4 drug-metabolizing enzymes in human liver microsomes. Methods : To use human liver microsomes, an extract of five herbal medicines, which are Artemisia princeps Pampan, Sophora jeponica Linne, Panax notoginseng F. H. Chen, Lithospermum Erythrorhizon Sieb., and Cirsium maackii Maxim, which together are called Jihyulyak(止血藥, drugs for arresting bleeding, hemostatics), was co-incubated and measured for relative enzyme activity in incubation condition compared to ketoconazole, a representative inhibitor of CYP 3A4. Results : We showed that all five of the traditional herbal medicines had no inhibition effect of CYP 3A4 at 10, 20, 30, 40, and $50{\mu}g/ml$ doses in human liver microsomes, although Sophora japonica Linne(SJL) showed a little inhibition at about 81% inhibition rate of control. However, this result is not enough to prove that SJL has a CYP 3A4 inhibition effect. Moreover, we can't make sure that those rates had significant induction effect on CYP 3A4. Conclusions : The result of this study could support that those herbal medicines are safer than chemical drugs, even if this is the basic step to prove that result.

• Korean Journal of Veterinary Research
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• v.44 no.2
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• pp.185-193
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• 2004

The effects of membrane lipid peroxidation and retinyl palmitate on rat liver microsomal functions were investigated in vitro. Rat liver homogenates exposed to oxygen tension for 0, 3, 6, 9 or12 hours and lipid peroxidation levels were evaluated by the measurements of fluorescence intensity, malondialdehyde (MDA) and retinyl palmitate. The fluorescence intensity of homogenates and microsomes were elevated and retinyl palmitate concentrations were decreased. But the concentration of MDA was not affected to exposure time. Therefore, fluorescence intensity and retinyl palmitate concentration were used to analyze the correlation between lipid peroxidation and microsomal functions. To investigate the liver microsomal functions, the microsome was isolated from rat liver homogenates exposed to oxygen. The concentration of cytochrome P450 and the activity of NADPH-cytochrome P450 reductase in liver microsomes were gradually decreased with increasing the exposure time. The correlation between fluorescence intensity of microsomes showed a very high inverse correlation of -0.97 and -0.93, respectively. The decrease of cytochrome P450 concentration was due to the regeneration of cytochrome P450 to cytochrome P420. Also, the activities of cytochrome P450-dependent aminopyrine demethylase and benzpyrene hydroxylase of liver microsomes were gradually decreased with increasing the exposure time. The correlation with fluorescence intensity of microsome showed a high inverse correlation of -0.97 and -0.91, respectively. The retinyl palmitate concentrations of rat liver homogenates were decreased with increasing the exposure time. The decrease of retinyl palmitate concentration was followed by a low concentration of cytochrome P450 and activity of NADPH-cytochrome P450 reductase. The correlation indicated high direct correlation of 0.92 and 0.93, respectively. The decrease of retinyl palmitate concentration was also accompanied by the reduction of aminopyrine demethylase and benzpyrene hydroxylase activities. The correlation was analyzed a high direct correlation of 0.90 and 0.85, respectively. In conclusion, these studies have shown that the membrane lipid peroxidation of rat liver microsome proportionally decreased microsomal enzyme activities in vitro experiments.

• Archives of Pharmacal Research
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• v.27 no.5
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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.

• Proceedings of the Korean Society of Applied Pharmacology
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• 2007.11a
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• pp.57-64
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• 2007

Metabolic interactions of the three major cannabinoids, ${\Delta}^9$-tetrahydrocannabinol (THC), cannabidiol (CBD), and cannabinol (CBN) with steroid hormones were investigated. These cannabioids concentration-dependently inhibited $3{\beta}$-hydroxysteroid dehydrogenase and $17{\alpha}$-hydroxylase in rat adrenal and testis microsomes. CBD and CBN were the most potent inhibitors of $3{\beta}$-phydroxysteroid dehydrogenase and progesterone $17{\alpha}$-hydroxylase, respectively, in rat testis microsomes. Three cannabinoids highly attenuated hCG-stimulated testosterone production in rat testicular interstitial cells. These cannabinoids also decreased in levels of mRNA and protein of StAR in the rat testis cells. These results indicate that the cannabinoids could interact with steroid hormones, and exert their modulatory effects on endocrine and testicular functions. Metabolic interaction of a THC metabolite, $7{\beta}$-hydroxy-${\Delta}^8$-THC with steroids is also investigated. Monkey liver microsomes catalyzed the stereoselective oxidation of $7{\beta}$-hydroxy-${\Delta}^8$-THC to 7-oxo-${\Delta}^8$-THC, so-called microsomal alcohol oxygenase (MALCO). The reaction is catalyzed by CYP3A8 in the monkey liver microsomes, and required NADH as well as NADPH as an efficient cofactor, and its activity is stimulated by some steroids such as testosterone and progesterone. Kinetic analyses revealed that MALCO-catalyze reaction showed positive cooperativity. In order to explain the metabolic interaction between the cannabinoid metabolite and testosterone, we propose a novel kinetic model involving at least three binding sites for mechanism of the metabolic interactions.

• YAKHAK HOEJI
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• v.59 no.5
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• pp.201-206
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• 2015

The aim of the present study was to optimize in vitro method for the prediction of drug-induced liver injury using human liver microsomes (HLM). Cytotoxicity test of cyclophosphamide and acetaminophen in HepG2 cells cultured with HLM showed that the newly established condition using 0.375 mg/ml HLM for 24 hr incubation was comparable or more sensitive than the previously established condition using 0.75 mg/ml HLM for 12 hr incubation. Although the cytotoxic effect of troglitazone was completely attenuated by 0.75 mg/ml HLM, it was augmented by 0.375 mg/ml HLM in the presence of the NADPH-generating system. The cytotoxic effect of chlormezanone, a withdrawn drug due to hepatotoxicity in human, was increased by HLM in the presence of the NADPH-generating system. In contrast, the cytotoxic effect of methapyrilene, a withdrawn drug due to hepatotoxicity in rats, was decreased by HLM in the presence of the NADPH-generating system. The present study suggests that the optimized in vitro method using HLM can be useful for the prediction of drug-induced hepatotoxicity.

• YAKHAK HOEJI
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• v.43 no.6
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• pp.834-842
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• 1999

The metabolism and pharmacokinetics of M-l, which is metabolite of pentoxifylline, have been studied in human liver microsomes. Biphasic kinetics was observed from the Eadie-Hofstee plot for the formation of both metabolites of M-l. For the kinetics of pentoxifylline, mean values of $V_{max1}{\;}and{\;}V_{max2}$ were 1,648 and 5,622 nmol/min/mg protein, and the estimated values of $K_{ml}{\;}and{\;}K_{m2}$ were 0.180 and 4.829 mM, respectively. For M-3, mean values of $V_{max1}{\;}and{\;}V_{max2}$ were 0.062 and 0.491 nmol/min/mg protein, and estimated values of $K_{ml}{\;}and{\;}K_{m2}$ were 0.025 and 1.216 mM. The formations of pentoxifylline and M-3 from M-1 were indentified by using several selective inhibitors of cytochrome P450 isoformes at 0.05-5 mM concentration of M-1 in human liver microsomes. For the analysis of low (0.05 mM) concentration of M-1, where the affinity was expected as low, indicated that CYPlA2 and CYP3A4 were major P450 isoforms responsible for pentoxifylline and M-3 formation. CYP3A4 and CYP2A6 appeared to be P450 isoforms responsible for M-3 formation at high (5 mM) concentration of M-1.

• Journal of Applied Biological Chemistry
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• v.43 no.1
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• pp.49-53
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• 2000

The in vitro metabolism of a new herbicide pyribenzoxim, {benzophenone O-[2,6-bis[(4,6-dimethoxy-2-pyrimidinyl)oxy]benzoyl]oxime} was studied using rice, barnyardgrass and rat liver microsomes. No metabolism of pyribenzoxim was observed with rice and barnyardgrass microsomes though the cvtochrome P450 was active, which was evidenced by the metabolism of cinnamic acid. With rat liver microsomes, four metabolites (M1, M2, M3, and M4) were produced while parent compound decreased. M1 and M2 were from the hydrolysis reactions and NADPH-dependent metabolites were M3 and M4 (major metabolite) which were hydroxylated by cytochrome P450. They were identified as bispyribac-sodium (M1), benzophenone oxime (M2), {benzophenone O-[2,6-bis[(5-hydroxy-4,6-dimethoxy-2-pyrimidinyl)oxy]-benzoyl]oxime}(M3), and {benzophenone O-[2[(5-hydroxy-4,6-dimethoxy-2l-pyrimidinyl)6-(4,.6dimethoxy-2-pyrimidinyl)oxy]benzoyl]oxime} (M4) through LC/MS/MS analyses. Based on the results obtained metabolic map of pyribenzoxim is proposed.

• Mass Spectrometry Letters
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• v.12 no.4
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• pp.172-178
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• 2021

HYIpro-3-1 is an adjuvant for preventing or treating inflammatory growth diseases. In this study, we identified the metabolic pathway of HYIpro-3-1 in human liver microsomes (HLMs) by quadrupole-orbitrap high-resolution mass spectrometry (HR-MS) and characterized the major human cytochrome P450 (CYP). Ten metabolites were identified, including one O-demethylation (M1), two O-demethylation and monohydroxylation (M2 and M3), and seven monohydroxylation metabolites (M4-M10). Based on the HR-MS² spectra, the metabolites are divided into two groups of monohydroxylated metabolites according to the hydroxylation position. We verified that HYIpro-3-1 is metabolized by CYP in HLMs, CYP2B6 is mainly involved in O-demethylation, and various CYPs are involved in the monohydroxylation of HYIpro-3-1.