• Environmental Analysis Health and Toxicology
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• 제22권3호
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• pp.227-233
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• 2007

It has been reported that hepatic glutathione (GSH) levels are decreased in diabetic patients, and glucagon increases hepatic efflux of GSH into blood. The signaling pathways responsible for mediating the glucagon effects on GSH efflux, however, are unknown. The signaling pathways involved in the regulation of GSH efflux in response to glucagon and insulin were examined in primary cultured rat hepatocytes. The GSH concentrations in the culture medium were markedly increased by the addition of glucagon, although cellular GSH levels are significantly decreased by glucagon. Insulin was also increased the GSH concentrations in the culture medium, but which is reflected in elevations of both cellular GSH and protein. Treatment of cells with 8-bromo-cAMP or dibutyryl-cAMP also resulted in elevation of the GSH concentrations in the culture medium. Pretreatment with H89, a selective inhibitor of protein kinase A, before glucagon addition markedly attenuated the glucagon effect. These results suggest that glucagon changes GSH homeostasis via elevation of GSH efflux, which may be responsible for decrease in hepatic GSH levels observed in diabetic condition. Furthermore, the present study implicates cAMP and protein kinase A in mediating the effect of glucagon on GSH efflux in primary cultured rat hepatocytes.

• Journal of Pharmaceutical Investigation
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• 제31권4호
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• pp.209-216
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• 2001

The purpose of the present study was to investigate the hepatic uptake and biliary excretion of l-anilino-8-naphthalene sulfonate (ANS) in vivo. The plasma concentration and liver concentration of ANS were determined after its i.v. bolus administration at a dose of $30\;{\mu}mol/kg$ in rats. The hepatic uptake clearance $(CL_{uptake})$ of ANS was 0.1 ml/min/g liver. On the basis of the unbound concentration of ANS, the permeability-surface area product $(PS_{influx})$ was calculated to be l0.4 ml/min/g liver, being comparable of in vitro data. On the other hand, we determined the plasma concentration, liver concentration and biliary excretion rate of ANS at steady-state after its i. v. infusion $(0.2-1.6\;{\mu}mol/min/kg)$ in rats. The excretion clearance $(CL_{excretion})$ of ANS showed Michaelis-Menten kinetics with increasing the infusion rate. The permeability-surface area product $(PS_{excretion})$ based on the unbound concentration in the liver was calculated to be 0.0165 ml/min/g liver, which is negligible compared with the intrinsic clearance $(CL_{int}=3.3\;ml/min/g\;liver)$ by rat liver microsomes. The sequestration process of ANS, therefore, was considered to be mainly due to the metabolic process in the liver $(PS_{seq}{\risingdotseq}CL_{int})$. Furthermore, $PS_{efflux}$ value calculated from $PS_{influx}$ and $PS_{seq}$ was 4.4 ml/min/g liver, which was comparable of in vitro data. In conclusion, in vivo parameters such as $PS_{influx}$, $PS_{efflux}$ and $PS_{seq}$ in the present study showed good in vivo-in vitro relationship. Thus, the kinetic analysis method proposed in the present study would be useful to analyze the hepatic transport of drugs in vivo.

• Archives of Pharmacal Research
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• 제26권4호
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• pp.338-343
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• 2003

The purpose of the present study was to investigate the bidirectional transport of 1-anilino-8-naphthalene sulfonate (ANS) using isolated rat hepatocytes. The initial uptake rate of ANS by isolated hepatocytes was determined. The uptake process of ANS was saturable, with a $K_m of 29.1\pm3.2 \mu M and V_{max} of 2.9\pm0.1$ mmol/min/mg protein. Subsequently, the initial efflux rate of ANS from isolated hepatocytes was determined by resuspending preloaded cells to 3.0% (w/v) BSA buffer. The efflux process for total ANS revealed a little saturability. The mean value of the efflux clearance was $2.2\pm0.1 \mu$ L/min/mg protein. The efflux rate of ANS from hepatocytes was markedly decreased at $4^{\circ}C$, indicating that the apparent efflux of ANS might not be attributed to the release of ANS bound to the cell surface, but to the efflux of ANS from intracellular space. The efflux clearance was furthermore corrected for the unbound intracellular ANS concentration on the basis of its binding parameters to cytosol. The relation between efflux rate and unbound ANS concentration was fitted well to the Michaelis-Menten equation with a saturable and a nonsaturable components. The $V_{max} and K_m$ values were 0.54 mmol/min/mg protein, and 10.0 $\mu$ M, respectively. Based on the comparison of the ratios of $V_{max} to K_m (V_{max}/K_m)$ corresponding to the transport clearance, the influx clearance was two times higher than the efflux clearance. Together with our preliminary studies that ATP suppression in hepatocytes substantially inhibited ANS influx rate, we concluded that the hepatic uptake of ANS is actively taken up into hepatocytes via the carrier mediated transport system.

• Nutrition Research and Practice
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• 제18권2호
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• pp.194-209
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• 2024

BACKGROUND/OBJECTIVES: High levels of plasma low-density lipoprotein (LDL) cholesterol are an important determinant of atherosclerotic lesion formation. The disruption of cholesterol efflux or reverse cholesterol transport (RCT) in peripheral tissues and macrophages may promote atherogenesis. The aim of the current study was to examine whether bioactive ellagic acid, a functional food component, improved RCT functionality and high-density lipoprotein (HDL) function in diet-induced atherogenesis of apolipoproteins E (apoE) knockout (KO) mice. MATERIALS/METHODS: Wild type mice and apoE KO mice were fed a high-cholesterol Paigen diet for 10 weeks to induce hypercholesterolemia and atherosclerosis, and concomitantly received 10 mg/kg ellagic acid via gavage. RESULTS: Supplying ellagic acid enhanced induction of apoE and ATP-binding cassette (ABC) transporter G1 in oxidized LDL-exposed macrophages, facilitating cholesterol efflux associated with RCT. Oral administration of ellagic acid to apoE KO mice fed on Paigen diet improved hypercholesterolemia with reduced atherogenic index. This compound enhanced the expression of ABC transporters in peritoneal macrophages isolated from apoE KO mice fed on Paigen diet, indicating increased cholesterol efflux. Plasma levels of cholesterol ester transport protein and phospholipid transport protein involved in RCT were elevated in mice lack of apoE gene, which was substantially reduced by supplementing ellagic acid to Paigen diet-fed mice. In addition, ellagic acid attenuated hepatic lipid accumulation in apoE KO mice, evidenced by staining of hematoxylin and eosin and oil red O. Furthermore, the supplementation of 10 mg/kg ellagic acid favorably influenced the transcriptional levels of hepatic LDL receptor and scavenger receptor-B1 in Paigen diet-fed apoE KO mice. CONCLUSION: Ellagic acid may be an athero-protective dietary compound encumbering diet-induced atherogenesis though improving the RCT functionality.

• Toxicological Research
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• 제29권3호
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• pp.165-172
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• 2013

Acetaminophen (APAP) known as paracetamol is the main ingredient in Tylenol, which has analgesic and anti-pyretic properties. Inappropriate use of APAP causes major morbidity and mortality secondary to hepatic failure. Overdose of APAP depletes the hepatic glutathione (GSH) rapidly, and the metabolic intermediate leads to hepatocellular death. This article reviews the mechanisms of hepatotoxicity and provides an overview of current research studies. Pharmacokinetics including metabolism (activation and detoxification), subsequent transport (efflux)-facilitating excretion, and some other aspects related to toxicity are discussed. Nuclear factor erythroid 2-related factor 2 (Nrf2)-regulated gene battery plays a critical role in the multiple steps associated with the mitigation of APAP toxicity. The role of Nrf2 as a protective target is described, and potential natural products inhibiting APAP toxicity are outlined. This review provides an update on the mechanism of APAP toxicity and highlights the beneficial role of Nrf2 and specific natural products in hepatoprotection.

• Toxicological Research
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• 제31권2호
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• pp.137-149
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• 2015

Human hepatocytes, with complete hepatic metabolizing enzymes, transporters and cofactors, represent the gold standard for in vitro evaluation of drug metabolism, drug-drug interactions, and hepatotoxicity. Successful cryopreservation of human hepatocytes enables this experimental system to be used routinely. The use of human hepatocytes to evaluate two major adverse drug properties: drug-drug interactions and hepatotoxicity, are summarized in this review. The application of human hepatocytes in metabolism-based drug-drug interaction includes metabolite profiling, pathway identification, P450 inhibition, P450 induction, and uptake and efflux transporter inhibition. The application of human hepatocytes in toxicity evaluation includes in vitro hepatotoxicity and metabolism-based drug toxicity determination. A novel system, the Integrated Discrete Multiple Organ Co-culture (IdMOC) which allows the evaluation of nonhepatic toxicity in the presence of hepatic metabolism, is described.

• 한국식품과학회지
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• 제54권4호
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• pp.398-402
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• 2022

본 연구에서는 폴리페놀 함유 블랙 초크베리가 콜레스테롤 대사에 미치는 영향을 HepG2 세포에서 콜레스테롤 대사 관련 유전자 발현을 측정함에 따라 조사하였다. 블랙 초크베리는 콜레스테롤 대사와 관련하여 콜레스테롤 흡수, 생합성, 유출과 관련된 유전자 발현을 조절하는 것으로 나타났다. 이는 블랙 초크베리의 혈중 콜레스테롤 저하 효과가 콜레스테롤 및 담즙 대사 관련 유전자 발현을 조절함에 의한 것으로 사료된다. 추후 블랙 초크베리 내 어떠한 생리활성물질이 콜레스테롤 대사 유전자 발현을 조절하여 이러한 효과를 나타내는 지에 대한 연구가 필요하며, 블랙 초크베리의 콜레스테롤 저하 효과를 동물 및 임상에서 기전 연구를 진행하여 천연 유래 기능성 소재로서의 블랙 초크베리의 중요성을 검증할 필요가 있을 것으로 사료된다.

• 한국식품영양과학회지
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• 제20권4호
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• pp.285-292
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• 1991

에탄올의 급성적 및 만성적 투여가 흰쥐의 간 및 소뇌 중의 glutathione(GSH) 양상과 지질과산화물 수준에 미치는 영향을 알아 본 결과는 다음과 같다. 간조직에서는, 만성적 에탄을 투여 (6~9g/kg, per day, 10% 음료수로서, 4주간)에 의해 총 GSH 농도가 14. 5% 저하되었고, 산화형 GSH(GSSG)는 변화가 없었으며, 따라서 GSSG/총 GSH 비율은 증가하였다. 그러나 지질과산화 수준은 변함이 없었다. 급성적 에탄올 투여에 의해 간 조직 중 지질과산화 수준이 상승되고 총 GSH 농도가 감소함은 이미 보고되고 있다. 본 실험에서는 이와 관련시켜 급성적 에탄을 투여 (50mmole/kg, i.p.)후 post-hepatic 혈장 중의 총 GSH 수준을 측정한 결과 현저히 상승하였다. 이러한 GSH의 간에서 혈액으로의 유출은, GSH의 항산화적 소모 이외에도, 급성적 그리고 아마도 만성적인 에탄을 투여에 의한 간 조직 중의 총 GSH의 감소의 한 가능한 원인으로서 간접적으로나마 추정될 수 있겠다. 소뇌에서 는 급성적 에탄을 투여는 지질과산화 수준을 증가시켰으나 GSH 양상은 변화시키지 않았으면, 만성적인 경우엔 모두 변동시키지 못하였다.

• Journal of Pharmaceutical Investigation
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• 제22권4호
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• pp.289-300
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• 1992

The counter-transport phenomena in the hepatic transport of 1-anilino-8-naphthalene sulfonate (ANS) were kinetically investigated by analyzing the plasma disappearance-time profiles and the transport into the isolated hepatocytes. In vivo "counter transport phenomena" were simulated based on the perfusion model which incorporated the carrier-mediated transport and the saturable intracellular binding. The condition that the mobility of carrier-ligand complex is greater than that of free carrier is not essential for the occurrence of counter-transport phenomenon. To examine the inhibitory effects on the initial uptake of a ligand by the liver, it is necessary to judge whether the true counter-transport mechanism (trans-stimulation) is working or not. The initial plasma disappearance curves of ANS were then kinetically analyzed based on a two-compartment model, in which the ligand is eliminated only from the peripheral compartment (liver compartment). No effects on the initial plasma disappearance rates of ANS were observed after preloading of bromophenol blue (BPB) or rose bengal (RB) in the liver. Inhibitory effect of BPB or RB on the initial uptake (or efflux) rates of ANS by the isolated hepatocytes were not observed, suggesting that the true counter transport mechanism is not working. In conclusion, checking the preloading effects of transstimulation on the initial uptake of a ligand by the liver could be a useful criterion for carrier cycling and common use of the same carrier between two ligands. However, one cannot exclude those possibilities even if the preloading effects cannot be observed.

• 한국식품영양과학회지
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• 제15권2호
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• pp.191-200
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• 1986

It is now generally accepted that individuals at increased risk for cardiovascular disease may be identified by certain traits or habbits. The factors such as high blood pressure, elevated blood cholestrol, age, sex and obesity are associated with increseaed frequency of disease. The blood cholesterol level lowering will decrease cardiovascular disease risk. The regression of atherosclerosis can be achieved by lowering the level of circulating cholesterol. Those things are connected with the quantity and quality of protein, fats, carbohydrates, especially soluble and non-soluble fiber, magnesium and calcium. The lipoprotein and lipid metabolism are connected with the lipid transport. The factors on lipid absorption and blood serum lipid pattern of human are exist. The factors have a variety of materials with different chemical and physical properties. The soluble fiber diet make a low blood and liver lipids. Many kind of soluble fiber results in a lowering of blood cholesterol and triglyceride levels. The cholesterol lowering effects of dietery fiber may be a results of alterations of in intestinal handling of fats, hepatic metabolism of fatty acid or triglyceride acid metabolism of lipoprotein. It is investigated that the high density lipoprotein (HDL) is inversely related to coronary artery disease. It has been postulated that HDL may be an important factor in cholesterol efflux from the tissues, therby reducing the amount of cholesterol deposited there. Alternatively, the HDL may pick up cholestyl ester and phospholipid during normal VLDL lipolysis in the plasma. The HDL levels are relatively insensitive to diet. At present time, the cause-and -diet effect of HDL's inverse relation to CHD remains unclear.