• Toxicological Research
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• 제2권1호
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• pp.1-7
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• 1986

Procarcinogen induced DNA single-strand breaks and unschduled DNA synthesis were measured in primary rat hepatocytes culture. For DNA single-strand breaks assay, rat liver DNA was prelabeled by injection 3H-thymidine during the peak of DNA synthesis following partial hepatectomy. Hepatocytes were isolated from the rat 2 weeks after surgery by a collagenase perfusion techinique and maintained as monolayers in serum free medium on collagen-coated culture dishes. DNA sigle-strand breaks were measured by the alkaline elution techinique.

• Archives of Pharmacal Research
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• 제22권5호
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• pp.474-478
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• 1999

Modulation of unscheduled DNA synthesis by dehydroepiandrosterone (DHEA) after exposure to various chemical carcinogens was investigated in the primary rat hepatocytes. Unscheduled DNA synthesis was induced by treatment of such direct acting carcinogens as methly methanesulfonate (MMS) and ethyl methanesulfonate (EMS) or procarcinogens including benzo(a)pyrene (BaP) and 7, 12-dimethylbenz(a)anthracene (DMBA). Unscheduled DNA synthesis was determined by measuring [methyl-3H]thymidine radioactivity incorporated into nuclear DNA of hepatocytes treated with carcinogens in the presence or absence of DHEA. Hydroxyurea $(5{\times}10^{-3} M)$was added to growth medium to selectively suppress normal replication. DHEA at concentrations ranging from $(1{\times}10^{-6} M)$ to$(5{\times}10^{-4} M)$ did not significantly inhibit unscheduled DNA synthesis induced by either MMS $(1{\times}10^{-4} M)$ or EMS $(1{\times}10^{-2} M)$. In contrast, DHEA-significantly inhibited unscheduled DNA synthesis induced by BaP $(6.5{\times}10^{-5} M)$ and DMBA.$(2{\times}10^{-5} M)$. DHEA-induced hepatotoxicity in rats was examined using lactate dehydrogenase (LDH) release as an indicator of cytotoxicity. DHEA exhibit no significant increase in LDH release compared with the control at 18 h. These data suggest that nontoxic concentration of DHEA does not affect the DNA excision repair process, but it probably influence the enzymatic system responsible for the metabolic activation of procarcinogens and thereby decreases the amount of the effective DNA adducts formed by the ultimate reactive carcinogenic species.

• Toxicological Research
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• 제4권2호
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• pp.131-142
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• 1988

The post-mitochondrial liver fractions (S-9) were prepared from rats and hamsters which have been treated with Aroclor 1254 (PCB) and the capacities of these S-9 fractions to generate mutagenic metabolites from several well known procarcinogens have been compared. Benzo(a)pyrene (B(a)P), 3-methylcholanthrene (3-MC), Aflatoxin B1(AFB1), 2-acetylamino-fluorene(AAF), and 2-aminofluorene (AF) were employed as promutagens in the Salmonella reverse mutation tests. Results showed that the rat and hamster S-9 fractions had differential abilities to produce mutagenic metabolites from a given promutagen.

• 한국독성학회:학술대회논문집
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• 한국독성학회 2003년도 추계학술대회
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• pp.169-169
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• 2003

CYP1 enzymes, CYP1A1, CYP1A2 and CYP1B1, are known to bioactivate procarcinogens particularly polyaromatic compounds. Flavonoids are a class of natural compounds that are present in edible plants. Structurally, these compounds are polyphenols with two aromatic rings (A, B) and a heterocycyclic ring (C).(omitted)

• 한국식품영양과학회지
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• 제27권5호
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• pp.968-972
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• 1998

Allium tuberosum Rotter(Liliaceae) is a perennial herb of which leaves are used for food. Leek has been reported to have pharmacological effects including alleviations of abdominal pain, diarrhea, hematemesis, snakebite, and asthma. To investigate the effect of dietary leek supplementation on the drug-metaboizing enzymes, quinone reductase(QR) and arylhydrocarbon hydroxylase(AHH) activities in the liver, stomach, small intestine and lung, and on the plasma testosterone and dihydrosterone hormone levels, mice were fed 2% and 5% leek diets for 8 weeks. Quinone reductase, an anticarcinogenic enzyme, was significantly induced in stomach, small intestine, and lung but slightly lowered in hepatic tissue in the experimental groups compared to control group. Arylhydrocarbon hydroxylase activity, involved in bioactivation of procarcinogens, was significantly decreased in liver and lung. Leek feeding led to the reduction in the plasma level of dihydrotestosterone which is associated with the incidence of prostate cancer. These findings support the potential chemopreventive activity of leek supplementation.

• 대한약학회:학술대회논문집
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• 대한약학회 2003년도 Proceedings of the Convention of the Pharmaceutical Society of Korea Vol.2-2
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• pp.112.2-112.2
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• 2003

CYP1 enzymes, CYP1A1, CYP1A2 and CYP1B1, are known to bioactivate procarcinogens particularly polyaromatic compounds. Flavonoids are a class of natural compounds that are present in edible plants. Structurally, these compounds are polyphenols with two aromatic rings (A, B) and a heterocycyclic ring (C). We observed the differential inhibition of 5,7-dihydroxyflavones which are different in numbers of B-ring-OH, to the activity of ethoxyresorufin O-deethylase (EROD) in human hepatic microsomes with the IC50 values, ie, 0.57 mM, 1.28 mM, and 3.62 mM, chrysin, apigenin, and Luteolin, respectively. (omitted)

• Archives of Pharmacal Research
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• 제23권4호
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• pp.267-282
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• 2000

Cytochrome P45O (CYP) 2E1 catalyzes the metabolism of a wide variety of therapeutic agents, procarcinogens, and low molecular weight solvents. CYP2E1-catalyzed metabolism may cause toxicity or DNA damage through the production of toxic metabolites, oxygen radicals, and lipid peroxidation. CYP2E1 also plays a role in the metabolism of endogenous compounds including fatty acids and ketone bodies. The regulation of CYP2E1 expression is complex, and involves transcriptional, post-transcriptional, translational, and post-translational mechanisms. CYP2E1 is transcriptionally activated in the first few hours after birth. Xenobiotic inducers elevate CYP2E1 protein levels through both increased translational efficiency and stabilization of the protein from degradation, which appears to occur primarily through ubiquitination and proteasomal degradation. CYP2E1 mRNA and protein levels are altered in response to pathophysiologic conditions by hormones including insulin, glucagon, growth hormone, and leptin, and growth factors including epidermal growth factor and hepatocyte growth factor, providing evidence that CYP2E1 expression is under tight homeostatic control.

• 한국식품과학회지
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• 제31권2호
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• pp.535-539
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• 1999

콩은 항에스트로젠효과와 항암효과를 가지는 것으로 나타나 최근 많은 관심의 대상이 되고 있다. 콩의 전립선암과 유방암 억제 기작으로 항에스트로젠 효과와 항안드로젠 효과가 보고되었지만 다른 조직에서 발현되는 항암활성 특히 화학적으로 유도되는 발암의 억제기작에 대해서는 아직 분명히 밝혀진 바가 없다. 본 연구에서는 콩이 생식기관이외에도 항암활성을 나타내리라 가정하고 그 기작을 규명하고자 하였다. 콩의 메탄올추추출물의 산가수분해물은 생쥐의 폐에서 항암효소계인 quinone reductase의 활성을 유의적으로 증가시켰으며 신장과 소장에서 1상효소계의 지표효소인 arylhydrocarbon hydroxylase효소활성을 억제하는 것으로 나타났다. 따라서 메탄올 추출물에 배당체로 존재하는 화합물이 산처리에 의하여 유리형으로 전환되면서 화학적 발암을 억제하는 활성을 획득하는 것으로 추정된다. 한편 benzo(a)pyrene으로 위암과 폐암을 유발시켰을 때, 콩추출물 첨가 식이는 폐암 발생을 현저히 낮추는 것으로 확인되었다. 이렇듯 화학적발암에 대한 콩 추출물의 방어효과는 약물대사효소계의 조절과 관련이 있는 것으로 추정된다.

• Archives of Pharmacal Research
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• 제27권2호
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• pp.199-205
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• 2004

Cytochrome P450 (P450) 1 enzymes such as P450 1A1, 1A2, and 181 are known to be involved in the oxidative metabolism of various procarcinogens and are regarded as important target enzymes for cancer chemoprevention. Previously, several hydroxystilbene compounds were reported to inhibit P450 1 enzymes and were rated as candidate chemopreventive agents. In this study, we investigated the inhibitory effect of 2-[2-(3,5-dimethoxyphenyl)vinyl]-thiophene (DMPVT), produced from the chemical modification of oxyresveratrol, on the activities of P450 1 enzymes. The inhibitory potential by DMPVT on the P450 1 enzyme activity was evaluated with the Escherichia coli membranes of the recombinant human cytochrome P450 1A1, 1A2, or 1B1 coexpressed with human NADPH-P450 reductase. DMPVT significantly inhibited ethoxyresorufin O-deethylation (EROD) activities with $IC_{50}$ values of 61, 11, and 2 nM for 1A1, 1A2, and 1B1, respectively. The EROO activity in OMBA-treated rat lung microsomes was also significantly inhibited by OMPVT in a dose-dependent manner. The modes of inhibition by DMPVT were non-competitive for all three P450 enzymes. The inhibition of P450 1B1-mediated EROD activity by OMPVT did not show the irreversible mechanism-based effect. The loss of EROD activity in P450 1B1 with OMPVT incubation was not blocked by treatment with the trapping agents such as glutathione, N-acetylcysteine, or dithiothreitol. Taken together, the results suggested DMPVT to be a strong noncompetitive inhibitor of human P450 1 enzymes that should be considered as a good candidate for a cancer chemopreventive agent in humans.