• Preventive Nutrition and Food Science
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• v.20 no.4
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• pp.238-245
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• 2015

A non-protein amino acid, L-ornithine (Orn), has been shown to stimulate the urea cycle and tissue protein synthesis in the liver. The purpose of the current study was to assess whether Orn affects the mammalian target of rapamycin (mTOR) complex 1 (mTORC1) pathway, which is involved in protein synthesis. Primary cultured cells isolated from Wistar rat liver were incubated in an amino acid-free medium, followed by addition of Orn for 3 h. The cell lysate was subjected to immunoblotting to evaluate the phosphorylation of downstream targets of mTORC1, including p70S6K, S6, and 4EBP1. To assess the involvement of mTORC1 for the effect of Orn, the cells were pretreated with the mTOR inhibitor rapamycin before the addition of Orn and the cell lysate was subjected to immunoblotting. We next examined whether the effects of Orn were exerted in vivo. Orn was orally administered to 18 h food-deprived rats, the blood and the livers were collected at 1 and 3 h after administration for immunoblotting. Orn treatment for primary cultured cells for 3 h enhanced the phosphorylation of p70S6K, S6, and 4EBP1. In addition, rapamycin blocked the effects of Orn completely (p70S6K and S6) or partially (4EBP1). The oral administration of Orn to the rat also augmented the phosphorylation of mTORC1 downstream targets notably in S6 at 1 h. Our findings demonstrate that Orn has the potential to induce the phosphorylation of downstream targets of mTORC1 in the rat liver. This may be mediated by the augmentation of mTORC1 activity.

• Environmental Mutagens and Carcinogens
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• v.23 no.2
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• pp.56-62
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• 2003

The liver progenitor cells could form a potential target cell population fore both tumor-initiating and -promoting chemicals. Induction of drug-metabolizing and antioxidant enzymes, including AhR-dependent CYP1A1, NQO-1 and AKR1C9, was detected in the rat liver epithelial WB-F344 "stem-like" cells. Additionally, WB-F344 cells express a functional, wild-type form of p53 protein, a biomarker of genotoxic events, and connexin 43, a basic structural unit of gap junctions forming an important type of intercellular communication. In this cellular model, two complementary assays have been established for detection of the modes of action associated with tumor promotion: inhibition of gap junctional intercellular communication (GJIC) and proliferative activity in confluent cells. We found that the PAHs and PCBs, which are AhR agonists, released WB-F344 cells from contact inhibition, increasing both DNA synthesis and cell numbers. Genotoxic effects of some PAHs that lead to apoptosis and cell cycle delay might interfere with the proliferative activity of PAHs. Contrary to that, the nongenotoxic low-molecular-weight PAHs and non-dioxin-like PCB congeners, abundant in the environment, did not significantly affect cell cycle and cell proliferation; however both groups of compounds inhibited GJIC in WB-F344 cells. The release from contact inhibiton by a mechanism that possibly involves the AhR activation, inhibition of GJIC and genotoxic events induced by environmental contaminants are three important modes of action that could play an important role in carcinogenic effects of toxic compounds. The relative potencies to inhibit GJIC, to induce AhR-mediated activity, and to release cells from contact inhibition were determined for a large series of PAHs and PCBs and their metabolites. In vitro bioassays based on detection of events on cellular level (deregulation of GJIC and/or proliferation) or determination of receptor-mediated activities in both ?$stem-like^{\circ}{\times}$ and hepatocyte-like liver cellular models are valuable tools for detection of modes of action of polyaromatic hydrocarbons. They may serve, together with concentration data, as a first step in their risk assessment.

• Korean Journal of Clinical Laboratory Science
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• v.39 no.3
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• pp.190-195
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• 2007

In the present study, the author investigated to the cytotoxocity in cultured rat hepatocytes of Viscum album lectin. The cytotoxcity effect in Viscum album lectin on the activity of LDH was also investigated. Viscum album lectin significantly increased LDH leakage into medium of hepatocytes treated or untreated with $CCl_4$ (p<0.001). However, Viscum album lectin significantly increased LDH leakage from $CCl_4$-induced hepatocyte (p<0.001). There was a significant increase in LDH levels relative to the control group. Histological observation basically supported the result obtained from LDH assay. The livers of rats challenged with $CCl_4$ produced a marked increased cytoplasmic vacuoles and inflammatory cells in number, while the number of necrotic cells and swollen hepatocytes did not change significnatly. Rats administered DMSO alone did not alter the normal hepatic architecture. Histological observation of liver section in rat treated 72 hrs with either Viscum album lectin $CCl_4$-induced liver damage showed number of cytoplasmic vaculoe and necrotic cell. The number of inflammatory cell increased markedly. This results suggest to the conclusion that Viscum album lectin has a effect of hepatotoxicity activator.

• Proceedings of the Korean Society of Applied Pharmacology
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• 1994.04a
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• pp.129-130
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• 1994

The science of toxicology is the understanding of the mechanisms by which exogenous agents produce deleterious effects in biological systems. The actions of chemicals such as drugs are ultimately exerted at the cellular and gene levels. Over the past decade. several in vitro alternative methods such as cultured cells for assessing the toxicity of various xenobiotics have been proposed to reduce the use of animals. In this workshop three advanced methods will be presented. These methods are novel important models for toxicologic studies. Dr. Tabuchis group has establishcd two immortalized gastric surface mucosa cell lines from the pminary cultore of gastric fundic mucosal cells of adult transgenic mice harboring a temperature sensitive simian virus 40 large T-anugen gene. As the immortalized cell lines of various tissues possess unique characteristics to maintain their normal functions for several months, these cell lines are extremely useful for not only toxicity testing but also pharmacological screening in new drug development. Professor Funatsu have studied the formation of spherical multicelluar aggregates of adult rat hepatocytes(spheroid) having tissue like structure. The sphcroid shown thre is a prototype module of an artificial liver support system. Thus, the urea synthesis activity of the artificial liver was maintained at least to days in 100％ rat blood plasma. Dr. Takezawa and his coworkers have developed a novel culture system of multicellular spheroids considered 〃organoids〃 by utilizing a thermo-responsive polymer as a substratum of anchorage dependent cells. His final goal is to reconstitute the organoids of various normal organs, e.g., liver, skin etc. and also abnormal deseased organs such as tumor.

• The Korean Journal of Physiology and Pharmacology
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• v.3 no.6
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• pp.565-570
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• 1999

Intracellular accumulation of bile acids in the hepatocytes during cholestasis is thought to be pathogenic in cholestatic liver injury. Due to the detergent-like effect of the hydrophobic bile acids, hepatocellular injury has been attributed to direct membrane damage. However histological findings of cholestatic liver diseases suggest apoptosis can be a mechanism of cell death during cholestatic liver diseases instead of necrosis. To determine the pattern of hepatocellular toxicity induced by bile acid, we incubated primary cultured rat hepatocytes with a hydrophobic bile acid, Glycochenodeoxycholate (GCDC), up to 5 hours. After 5 hours incubation with $400\;{\mu}M$ GCDC, lactate dehydrogenase released significantly. Cell viability, quantitated in propidium iodide stained cells concomitant with fluoresceindiacetate was decreased time- and dose-dependently. Most nuclei with condensed chromatin and shrunk cytoplasm were heavily labelled time- and dose-dependently by a positive TUNEL reaction. These findings suggest that both apoptosis and necrosis are involved in hepatocytes injury caused by GCDC.

• Korean Journal of Environmental Biology
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• v.22 no.1
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• pp.141-147
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• 2004

In order to investigate whether or not the alcohol-treated rat liver cells can be protected by Korean Citrus junos and medicinal herbs, We compared the serum biochemistry of rats administered both alcohol and the complex of Korean Citrus junos and medicinal herbs to control rats treated with alcohol alone. The activities of Aspartate aminotransferase (AST) and Alanine aminotransferase (ALT) in the citron 3 (Citron 3, less mellowed citron which was ripened for three months)＋Phellinus linteus, Alnus japonica, Dendropanax morbifera and citron 4 (Citron 4, completely mellowed citron which was ripened fer four months)＋Phaseolus radiatus, Cordyceps militaris group were significantly low when compared with the negative control group (p<0.05). The levels of triglyceride (TG) in all experimental groups were significantly lower than the negative control group (p<0.05). The concentrations of total cholesterol in the citron 3＋Phellinus linteus, Atnus japonica, Dendropanax morbifera and citron 4＋Phaseolus radiatus, Cordyceps militaris, Phellinus linteus were lower than the negative control group (p<0.05). The activities of alcohol dehydyogenase (ADH) in all experimental groups were significantly high when compared with the normal control group (p<0.05). These results suggest that the complex of Korean Citrus junos and medecinal herbs could be an excellent candidate for protecting vat liver cell damage induced by alcohol.

• Molecular & Cellular Toxicology
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• v.2 no.2
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• pp.120-125
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• 2006

Phenytoin is an anti-epileptic. It works by slowing down impulses in the brain that cause seizures. The recent microarray technology enables us to understand possible mechanisms of genes related to compounds which have toxicity in biological system. We have studied that the effect of a compound related to hepatotoxin in vitro system using a rat whole genome microarray. In this study, we have used a rat liver epithelial cell line WB-F344 and phenytoin as a hepatotoxin. WB-F344 was treated with phenytoin for 1 to 24 hours. Total RNA was isolated at times 1, 6 and 24h following treatment of phenytoin, and hybridized to the microarray containing about 22,000 rat genes. After analysis with clustering methods, we have identified a total of 1,455 differentially expressed genes during the time course. Interestingly, about 1,049 genes exhibited differential expression pattern in response to phenytoin in early time. Therefore, the identification of genes associated with phenytoin in early response may give important insights into various toxicogenomic studies in vitro system.

• The Korean Journal of Physiology and Pharmacology
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• v.4 no.2
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• pp.121-127
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• 2000

Intracellular accumulation of bile acids in the hepatocytes during cholestasis is thought to be pathogenic in cholestatic liver diseases. The objective of this study was to determine the role of lipid peroxidation and glutathione on the bile acid-induced hepatic cell death mechanism in primary cultured rat hepatocytes. To induce hepatic cell death, we incubated primary cultured rat hepatocytes with glycochenodeoxycholic acid $(GCDC;\;0{\sim}400\;{\mu}M)$ for 3 hours. In electron microscopic examination and agarose gel electrophoresis, low concentration of GCDC treatment mainly induced apoptotic feature. Whereas $400\;{\mu}M$ GCDC treated cells demonstrated both apoptosis and necrosis. Lipid peroxidation was increased dose-dependently in GCDC treated hepatocyte. And this was also accompanied by decreased glutathione. Therefore, oxygen free radical damage may play a partial role in GCDC-induced hepatic cell death.

• Korean Journal of Environmental Biology
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• v.20 no.2
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• pp.173-179
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• 2002

N-nitrosoethylurea (NEU) -induced changes of lipid peroxide content, aldehyde metabolic enzyme activities and antioxidant enzyme activities were examined in cultured rat liver cell. Aldehyde metabolic enzymes tested in this investigation were alcohol dehydrogenase and aldehyde dehydrogenase. Several antioxidant enzymes tested were glutathione transferase, superoxide dismutase, glutathione reductase and catalase. When the cell was exposed with various concentrations of NEU, lipid peroxide content increased about 2.5 fold with 6.25 mM NEU. Maximun 2.3 times higher alcohol dehydrogenase activity was found after NEU treatment. About 2 times higher aldehyde dehydrogenase activity could also be observed. Only slight increases of glutathione transferase and catalase activities occurred with NEU treatment. In addition mnximun 1.5 times higher superoxide dismutase activities and 3 times higher glutathione reductase activities were found after NEU treatment. Therefore, it is likely that the increases of superoxide dismutase and glutathione reductase could contribute in a antioxidative process against NEU toxicity.

• Korean Journal of Veterinary Research
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• v.38 no.3
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• pp.606-613
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• 1998

Cadmium is one of the well-known environmental toxicants and induces cancer in rodents and human, but its carcinogenic mechanism has not been well demonstrated until now. Genotoxic effects of cadmium in Salmonella typhimurium TA98, TA100 and TA1535/pSK1002 or in WB-F344 rat liver epithelial cells were investigated to elucidate the tumor initiating effects of cadmium. TA98, TA100 and TA1535/pSK1002 tester strains were used to detect frameshift mutation, base-pair mutation and SOS repair response, respectively, in Salmonella mutation test. Reverse mutations from histidine to $histidin^+$ of Salmonella typhimurium TA98 and TA100 by $CdCl_2$ were not significantly different from control up to the maximum doses ($100{\mu}M$ and $200{\mu}M$ in TA98 and TA100, respectively) at which non-cytotoxicity was observed. DNA SOS repair responses(${\beta}$-galactosidase activity) generally did not show significant increases compared to control in both of the conditions with or without metabolic activation in Salmonella typhimurium TA1535/pSK1002 by $CdCl_2$. But the activities of ${\beta}$-galactosidase by $400{\mu}M$ of $CdCl_2$ in metabolic activation condition and by 130 and $400{\mu}M$ of $CdCl_2$ in non-metabolic activation condition were more decreased than those of control. DNA single strand breaks for 4hrs were observed only in WB-F344 rat liver epithelial cells treated with $200{\mu}M$ of $CdCl_2$. As a conclusion, $CdCl_2$ did not induce gene mutation in microbials but induce DNA single strand breaks in rat liver epithelial cells.