• 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.

• Toxicological Research
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• v.11 no.2
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• pp.273-277
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• 1995

Several metabolic modulators on the generation of carbon monoxide (CO)from dichloromethane (DCM) was examined in adult female rats. It has been known that DCM is converted to CO by cytochrome P-450 or to carbon dioxide $(CO_2)$ by glutathione-dependent metabolic reaction. In rats treated with DCM (3 mmol/kg, ip) only, the carboxyhemoglobin (COHb) level reached a peak of approximately 10% 2 or 3 hr following the treatment. Disulfiram (300 mg/kg, ip) or allylsulfide (200 mg/kg, po), both known as a selective inhibitior for cytochrome P-450 2E1, blocked the increase in COHb concentratlons almost completely suggesting that the metabolic conversion of DCM to CO is mediated by the activity of this specific type of isozyme. YH439 (125 or 250 mg/kg, po), a potential hepatoprotective agent, decreased the COHb elevation as well indicating that this chemical is a potent inhibitor for 2E1. In rats treated with pyrazine (200 mg/kg, ip) 18 hr prior to DCM the peak COHb concentration was decreased by approximately 3 or 4%. However, pretreatment of rats with pyrazine either 24 or 48 hr before DCM increased the peak COHb concentration significantly compared to the rats treated with DCM only. The results in the present study strongly suggest that the generation of CO from DCM depends on the 2E1 activity and that the pharmacological and/or toxicological action of YH439 or pyrazine in animals or human is associated with its effect on this isozyme.

• YAKHAK HOEJI
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• v.44 no.5
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• pp.379-383
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• 2000

Stanozolol (STZ, 17$\alpha$-methyl-17$\beta$-hydroxy-5$\alpha$-androstano-(3,2-c) pyrazole), an anabolic steroid, is an abused drug by body-builders or atheletes, as well as medicine for treatment of aplastic anemia and vascular thrombosis. In human volunteers, the major urinary metabolite of STZ was reported to be 3'-hydroxystanozolol that was identified by gas chromatography-mass selective detector (GC/MSD). The objective of this experiment is to investigate the in vitro metabolism of STZ in liver S-9 faction of polychlorinated biphenyl-induced rats. Reaction mixture including STZ as substrate and the S-9 faction was extracted with diethyl ether and quantified by the selected ion monitoring mode of GC/MSD. The selected concentration of substrate STZ is 100 nmole and the selected time for incubation in the reaction mixture was determined to 60 min. The amount of 3'-hydroxystanozolol produced was increased by about 6-fold in the reaction medium including the liver S-9 fraction of polychlorinated biphenyl-induced rats, compared to that of untreated rats. Inhibitors of cytochrome P450, SKF-525A and 7,8-benzoflavone, decreased the production of 3'-hydroxystanozolol by about 89~100% and 65~75%, respectively; In conclusion, hydroxylation of STZ into 3'-hydroxystanozolol is confirmed by GC/MSD and is catalyzed by cytochrome P450.

• Journal of Ginseng Research
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• v.33 no.3
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• pp.212-218
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• 2009

Triterpenoid saponins were synthesized in Panax ginseng C.A. Meyer via the isoprenoid pathway by cyclization of 2,3-oxidosqualene to give primarily oleanane (beta-amyrin) or dammarane triterpenoid skeletons. The triterpenoids are backbone and undergoes various modifications (oxidation, substitution and glycosylation), mediated by cytochrome P450 (CYP)-dependent monooxygenases, glycosyltransferase and other enzymes. This is likely to be due in part to the complexity of the molecules and the lack of pathway intermediates for biochemical studies. A cDNA clone encoding a putative CYP gene was isolated from flower bud of ginseng and transformed into the plant(Nicotiana tabacum cv. Xanthi) and confirmed by PCR analysis. The CYP gene (PgCYP) contained an open reading frame(ORF) encoding mature protein of 500 amino acids. The expression of PgCYP were investigated in transgenic tobacco by reverse transcriptase-polymerase chain reaction (RT-PCR).

• Journal of Life Science
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• v.8 no.5
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• pp.604-613
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• 1998

The last enzyme of the sesquiterpen phytoalexin capsidiol synthesis in tobacco cell, 5-epi-aristolochene hydro-xylase which convert 5-epi-aristolochene (EAS) to capsidiol, was cloned by a reverse transcription polymerase chain reaction strategy and cDNA library screening. Cloned CYP-B3 contained high probability amino acid matches to known plant cytochrome P450 sequences and open reading frame with the conserved FxxGxRxCxG heme-binding region. Transcripts of CYP-B3 were not detected in control cells, but induced in elicitor-treated cells. Furthermore, CYP-B3 transcripts were induced by fungal extracts and cellulase but not by other stimuli(chilling, heat shock and 2,4-D). Induction of CYP-B3 transcripts by elicitor treatment was not affected by ancymidol and ketoconazole treat-ments suggesting that an inhibition of hydroxylase activity by Cyt P450 inhibitors resulting from post translational processing event.

• Journal of the Korean Society of Tobacco Science
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• v.20 no.2
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• pp.178-182
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• 1998

Previously, we showed that acetone enhanced aryl hydrocarbon hydroxylase (AHH) activity in only 3-methylcholanthrene (MC)- or $\beta$-naphtoflavone (BNF)-inducible microsomes of rat liver. In the present study, the possible mechanism underlying acetone action on AHH was investigated in the liver microsomes from MC-pretreated rats. Other n-alkylketones except acetone did not increase AHH activity, which rather decreased significantly with the length of alkyl side chain. Acetone had no effect on the activity of NADPH-cytochrome P450 reductase or inhibited the formation of 3-OH benzo(a)pyrene (B(a)P) in nonenzymatic model ascorbic acid system. However, in cumene hydroperoxide (CuOOH)-supported B(a)P hydroxylation, acetone enhanced its velocity remarkably by 30% at the optimal concentration (30 $\mu$M CuOOH and 1.0% acetone). From these results, we conclude that acetone may facilitate the formation of an activated oxygen species or the insertion of oxygen into B(a)P molecule in CYP1A rich microsomes.

• Archives of Pharmacal Research
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• v.8 no.3
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• pp.119-132
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• 1985

The apparent effectiveness of 1-naphthyl-N-methyl carbamate (carbaryl) against a wide variety of insects motivated the study of its mammalian toxicity. In this toxicological study of carbaryl, mature male rats inhaled carbaryl at a mean concentration of 112mg, 168mg and 224 mg/$m^{3}$ for one hour. After inhalation, pentobarbital sleeping time, Nadph-cytochrome c reductase activity, cytochrome p-450 and protein content in liver microsomes, various tissue residues, cholinesterase inhibition in plasma and histopathological findings at autopsy were observed. The pentobarbital sleeping time was prolonged in rats inhaled with carbaryl for one day while the sleeping time was shortened in the 3 days inhaled group. The changes of cytochrome p-450 content and NADPH-cytochrome c reductase activity exhibited biphasic response showing the decrease in the one day inhaled group and the increase in the 3 days inhaled group. The marked depression of plasma ChE activity was observed in rats inhaled with carbaryl at 112 mg/$m^{3}$, however no more progressive effect was observed at the higher concentration of the compound. The main observations in histopathological finding were ciliary detachment, epithelial swelling and subepithelial inflammatory cellular infiltration in trachea due to the irritation.

• Archives of Pharmacal Research
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• v.26 no.5
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• pp.394-404
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• 2003

Certain polycyclic aromatic hydrocarbons (PAHs) have been reported to induce cytochrome P450 (CYP) 1A1 and 1A2. In the present study, the effects of six well-known PAHs, such as benzo[a]pyrene, benz[a]anthracene, dibenz[a,h]anthracene, chrysene, benzo[k]fluorancene and benzo[b]fluorancene, on the activities of hepatic and pulmonary CYP enzymes were investigated in male ICR mice. When mice were treated intraperitoneally with 3, 10 and 30 mg/kg of individual PAHs for 3 consecutive days, the activities of ethoxyresorufin- and methoxyresorufin-Ο-dealkylases were significantly and differentially induced in both liver and lung. Moreover, other CYP isozyme-associated monooxygenase activities were also induced significantly in liver and lung with characteristic induction profiles. Our present results suggest that individual PAHs might have inductive effects on CYP isozymes, and that the characteristic inductive effects of individual PAHs on certain CYP isozymes would be developed as a marker for determining exposure to certain PAHs.

• Toxicological Research
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• v.30 no.3
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• pp.179-184
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• 2014

Xenobiotics causing a variety of toxicity in biological systems could be classified as two types, inorganic and organic chemicals. It is estimated that the organic xenobiotics are responsible for approximately 80~90% of chemical-induced toxicity in human population. In the class for toxicology, we have encountered some difficulties in explaining the mechanisms of toxicity caused especially by organic chemicals. Here, a simple flowchart was introduced for explaining the mechanism of toxicity caused by organic xenobiotics, as the central dogma of molecular biology. This flowchart, referred to as a central dogma, was described based on a view of various aspects as follows: direct-acting chemicals vs. indirect-acting chemicals, cytochrome P450-dependent vs. cytochrome P450-independent biotransformation, reactive intermediates, reactivation, toxicokinetics vs. toxicodynamics, and reversibility vs. irreversibility. Thus, the primary objective of this flowchart is to help better understanding of the organic xenobiotics-induced toxic mechanisms, providing a major pathway for toxicity occurring in biological systems.

• Mass Spectrometry Letters
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• v.3 no.4
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• pp.104-107
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• 2012

Mollugin isolated from Rubia cordifolia is known to have anti-inflammatory, anti-cancer, and anti-viral activities. In the present study, a cocktail probe assay and LC-MS/MS were used to investigate the modulating effect of mollugin on cytochrome P450 (CYP) enzymes in male ICR mice. After mollugin was orally administrated to mice at the 20, 40, or 80 mg/kg for 3 days, the activities of CYP in hepatic S-9 fractions were investigated. Unlike the selective inhibitory effect of mollugin on CYP1A2-catalyzed phenacetin O-deethylation in vitro, mollugin only significantly inhibited the activity of CYP2E1-catalyzed chlorzoxazone 6-hydroxylase in vivo. The activities of other CYPs were only slightly altered by mollugin. The results of this study suggest that mollugin might cause herb-drug interactions via the selective inhibition of CYP2E1 in vivo.