• Biomolecules & Therapeutics
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• v.3 no.1
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• pp.21-27
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• 1995

The only compounds with antagonistic activity via AT$_1$receptor, one of two subtypes of angiotensin II (AII) receptor, have been demonstrated to block the vasoconstriction effects of AII and thereby provide therapeutic potential. This initiated the search for compounds with high specific affinity to AT$_1$receptor and their effective screening methods. The radioligand binding assay for the AII receptor is regarded as the primary method for the evaluation of AT$_1$receptor antagonists for their activity. In this paper, we characterized the liver AT$_1$receptor and describe the efficient method of the radioligand binding assay using rat liver as a source of AT$_1$receptor. Equilibrium binding studies with rat adrenal cortex, adrenal medulla, liver and bovine adrenal showed that the specific bindings of [$^3$H] AII were saturable in all tissues and the Scatchard plots of those data were linear, suggesting a single population of binding sites. Hill slopes were very near to the unity in all tissues. Kinetic studies of [$^3$H) AII binding in rat liver homogenates yielded two association rate constants, 4.10$\times$10$^{7}$ M$^{-1}$ min$^{-1}$ and 4.02$\times$10$^{9}$ M$^{-1}$ min$^{-1}$ , with a single dissociation rate constant, 7.07$\times$10$^{-3}$ min-$^{-1}$ , possibly due to the partial dissociation phenomenon. The rank order of inhibition potencies of [$^3$H] AII binding in rat liver was AII>Sarile>Losartan>PD 123177. Rat liver homogenates revealed to have very high density of homogeneous population of the AT$_1$receptor subtype, as the specifically bound [$^3$H] AII was not inhibited by PD 123177, the nonpeptide antagonist of AT$_2$. The results of this study demonstrated that the liver homogenates from rats could be the best receptor preparation for the AT$_1$receptor binding assay and provide an efficient system for the screening of newly synthesized candidate compounds of AT$_1$receptor antagonist.

• Korean Journal of Veterinary Research
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• v.43 no.3
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• pp.383-392
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• 2003

Insulin-like growth factors (IGFs) and their binding proteins (IGFBPs) are important regulators on the development of maternal tissues during pregnancy. This study was performed to examine the relationship between maternal IGFs/IGFBPs system (i.e: IGF-I, II, their receptors, and IGFBPs) in pre- and post-partum rats. The liver and kidney are important organs for the synthesis of IGFs and IGFBPs in adults. The levels of materanal IGFs and IGFBPs in serum, liver, and kidney were examined at 14 and 21 days of gestation and at 3, 7, 11, and 14 days after birth. The expression of IGFs and their receptors mRNA was also examined in fetal and maternal rat liver, kidney. IGF-I concentrations in maternal serum and liver were decreased during pregnancy. However, IGF-I concentration in maternal kidney was increased, having maximal effect at 14 days of gestation. IGF-I concentrations were decreased in serum, liver, and kidney of postpartum rat, compared to control (p < 0.05). On the other hand, IGF-II concentrations in serum, liver, and kidney were increased during pregnancy (p<0.05) and gradually decreased to control level in postpartum period. The levels of IGFBP-3 and IGFBP-2 are expressed in serum, liver, and kidney. However, IGFBP-3 is mainly expressed in serum and liver, and IGFBP-2 in kidney. The levels of IGFBP-3 and IGFBP-2 in maternal serum were markedly decreased during pregnancy and gradually recovered to control level during postpartum period by western ligand blotting. However, there was no change of IGFBP-3 and IGFBP-2 levels by western immunoblotting. The levels of IGFBP-3 and IGFBP-2 in maternal liver and kidney also showed the same pattern of serum, although the main IGFBP is different. In normal rat serum, IGF-I 150 kDa and 50 kDa carrier proteins were detected. The level of IGF-I 150 kDa carrier proteins in pregnant rat was decreased compared to normal rat, but that of 50 kDa carrier proteins was increased. IGFBP-3 protease activity was identified in pregnant rat serum and maternal placenta, and it was inhibited by EDTA ($Ca^{2+}$ chelating agent) and aprotinin (serine proteinase inhibitor). Taken together, these results suggest that the changes of IGFs and IGFBPs in maternal rats are regulated by liver and kidney IGFs and their receptors mRNA during the pregnancy.

• Toxicological Research
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• v.5 no.1
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• pp.27-35
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• 1989

When acetaminophen (25mM) was introduced into the perfused rat liver, the hepatic O2 uptake was rapidly inhibited first and then later slow-down. The rapid inhibition was found to be due to mitochondrial blockade, whereas the so-called slow inhibition" was associated with microcirulatory aberrations as evidenced by inhomogneous staining of the liver tissue by trypan blue infusion (0.1%). NaCN (0.5mM) also caused rapid and slow respiratory inhibitions, giving heterogeneous trypan blue staining.ning.

• Archives of Pharmacal Research
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• v.8 no.3
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• pp.149-157
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• 1985

The HCL hydrolyzate of the non-histone protein fractionated from the rat liver nuclei which have been incubated inthe presence of S-adenosyl-L-[methyl-$^{14}C$ ]-methionine shows at least four unidentified radioactive peaks on a basic amino acid analysis chromatogram. One of these unknown compounds (designated as compound 3) is also formed by the rat liver homogenated with the exogenous addition of an appropriate protein substrate. Since boiled rat liver homogenate or fresh homogenate in the absence of an exogenous protein substrate failed to form compound 3, its formation can be considered to be enzyme-catalyzed. The enzyme which yields compound 3 shows a preference of protein substrate in the order of reductively methylated hemoglobin > native > histone type II-A. The rat enzyme is nuclear in location associated with chromatin, and exhibits the highest activity in the liver among various rat organs. A compound 3-forming enzyme is also present in Neurospora crassa, since endogenous formation of the compound 3 can be demonstrated with the crude extract of this mold. The chemical identity of compound 3 is not yet known. However, it resisted to the following treatments; 6 N HCL and 0.1 N Na NaOH hydrolysis at $110^{\circ}C$, OR L-amino acid oxidase.

• Applied Microscopy
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• v.18 no.2
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• pp.205-217
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• 1988

An ultrastructural study of hepatocyte proliferation in the regenerating rat liver has been made by means of the partial hepatectomy. And electron microscopic histochemistry of hepatocyte in the regenerating rat liver is studied through alkaline phosphatase reaction. The results are as follows: 1. When the regeneration of rat liver is induced by the partial hepatectomy, the prominent ultrastructural characteristics of hepatocyte are changes of the distribution of chromatin in nucleus, increase of the number of mitochondria and decrease of the size of them, development of rough endoplasmic reticulum, and transient decrease of glycogen granules in cytoplasm. 2. Alkaline phosphatase reaction products are appeared in the nucleus or rough endoplasmic reticulum of hepatocyte during the initial regeneration of liver as 24, 48 and 72 hour groups after partial hepatectomy. And these positive reaction are mainly increased in cytoplasm and plasma membrane of hepatocytes during 1, 2 and 3 week groups after partial hepatectomy. As 4 weeks passed after partial hepatectomy, these positive reaction is located in the sinusoidal epithelial cells or erythrocytes. With above results, we concluded that alkaline phosphatase was synthesized in the rough endoplasmic reticulum bounded ribosomes of regenerating hepatocyte, was transported to the plasma membrane of them, and then was transported in blood by the way sinusoidel epithelial cells.

• Molecular & Cellular Toxicology
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• v.3 no.4
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• pp.299-305
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• 2007

The endocrine disrupting chemical, di (2-ethylhexyl) phthalate (DEHP) is a plasticizer used in polyvinyl chloride products ubiquitous in our daily lives. DEHP has potentially adverse effects on the liver, kidney, lung, heart, reproductive organs and endocrine systems. Many toxicological data on the DEHP toxicity have been stated, but complete protein profiles have not yet been reported. In this study, DEHP-induced oxidative DNA damage in rat lymphocyte was evaluated by Comet assay (single-cell gel electrophoresis) for the first time. Moreover, DEHP-induced protein profile alterations were examined in rat liver by using toxicoproteomic tools. 34 protein spots in the liver were identified to be significantly deregulated by DEHP on the 2-dimensional gel. Among them, 20 spots were up-regulated and 14 spots down-regulated by DEHP.

• Journal of Nutrition and Health
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• v.27 no.10
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• pp.1007-1017
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• 1994

In order to investigate the effect of Korean green tea, oolong tea and black tea beverage on the antioxidative detoxification in cadmium(Cd) poisoned rat liver, male Sprague-Dawley rat weighing 143$\pm$3.2g were divided into control and experimental groups. The experimental groups were fed standard diet containing 40ppm Cd and were given distilled water(CD), 5% black tea(BT), oolong tea(OT) and green tea(GT), respectively. Tea beverages were extracted from 5G dry leaves of teas in 100ml hot distilled water by the treatment at 85$^{\circ}C$ for 3 min. Liver xanthine oxidase(XOD) activity was increased by the administration of Cd except GT group. Liver superoxide dismutase(SOD), glutathione peroxidase(GSH-px), glutathione S-transferase(GST) activities were decreased by te administration of Cd but did not decreased by the administration of green tea(in GT group). Vitamin E and reduced glutathione contents were significantly decreased in Cd administered groups. Liver lipid peroxide value in Cd administered groups were increased compared to control group, but was not increased in GT group. Serum glutamic oxaloacetic transaminase(GOT) activities in CD, OT, BT groups were higher than control, but that in GT group was similar to control group. Serum glutamic pyruvic transaminase(GPT) activity was not significantly different among various groups. It was concluded that green tea might alleviate peroxidative damage in Cd-administered rat liver by reinforcing antioxidative detoxification system.

• Environmental Mutagens and Carcinogens
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• v.25 no.3
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• pp.97-103
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• 2005

The genotoxic effect of antimalarial drugs amodiaquine (AQ), mefloquine (MQ) and halofantrine (HF) was investigated in.at liver cells using the alkaline comet assay. AQ, MQ and HF at concentrations between $0-1000{\mu}mol/L$ significantly increased DNA strand breaks of rat liver cells dose-dependently. The order of induction of strand breaks was AQ>MQ>HF. The rat liver cells exposed to AQ and HF (200 and 400 ${\mu}mol/L$) and treated with (Fpg) the bacterial DNA repair enzyme that recognizes oxidized purine showed greater DNA damage than those not treated with the enzyme, providing evidence that AQ and HF induced oxidation of purines. Such an effect was not observed when MQ was treated with the enzyme. Treatment of cells with catalase, an enzyme inactivating hydrogen peroxide, decreased significantly the extent of DNA damage induced by AQ, and HF but not the one induced by MQ. Similarly quercetin, an antioxidant flavonoid at $50{\mu}mol/L$ attenuated the extent of the formation of DNA strand breaks by both AQ and HE. Quercetin, however, did not modify the effects of MQ. These results indicate the genotoxicity of AQ, MQ and HF in rat liver cells. In addition, the results suggest that reactive oxygen species may be involved in the formation of DNA lesions induced by AQ and HF and that, free radical scavengers may elicit protective effects against genotoxicity of these antimalarial drugs.

• Biomolecules & Therapeutics
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• v.16 no.1
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• pp.34-39
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• 2008

Oxidative stress may represent a common link between chronic liver damage and hepatic fibrosis. In the present study, we investigated activity changes of sphingomyelin catabolic enzymes, such as sphingomyelinases and ceramidases by using dimethylnitrosamine (DMN)-treated Sprague-Dawley (SD) male rats hepatic fibrosis model as a hepatic fibrosis model. Twenty rats divided into five groups received: (1) saline; (2) DMN for 1 week, (3) DMN for 2 weeks, (4) DMN for 3 weeks, and (5) DMN for 4 weeks by intraperitoneally 10 mg/kg of body weight for three consecutive days a week. Activities of acidic and neutral sphingomyelinases and acidic, neutral and alkaline ceramidases were measured in the liver and kidney from DMN-treated rats. We found increased ceramidase activities from 2-week and/or 3-week DMN treated rat livers compared to control rat liver. Acidic sphingomyelinase and alkaline ceramidase activities were significantly increased in 3-week DMN-treated rat kidneys compared to control rat kidney. Therefore, sphingolipid metabolizing enzymes and sphingolipid metabolites are supposed to be involved in liver fibrosis, although further investigation is necessary to elucidate meanings of sphingolipids during the liver fibrosis

• Asian Pacific Journal of Cancer Prevention
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• v.17 no.12
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• pp.5071-5074
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• 2016

Background: Azoxymethane (AOM) is a well-known colon cancer-inducing agent in experimental animals via mechanisms that include oxidative stress in rat colon and liver tissue. Few studies have investigated AOM-induced oxidative stress in rat liver tissue. Red seaweeds of the genera Hypnea Bryodies and Melanothamnus Somalensis are rich in polyphenolic compounds that may suppress cancer through antioxidant properties, yet limited research has been carried out to investigate their anti-carcinogenic and antioxidant influence against AOM-induced oxidative stress in rat liver. Objective: This study aims to determine protective effects of red seaweed (Hypnea Bryodies and Melanothamnus Somalensis) extracts against AOM-induced hepatotoxicity and oxidative stress. Materials and Methods: Sprague-Dawley rats received intraperitoneal injections of AOM, 15 mg/kg body weight, once a week for two consecutive weeks and then orally administered red seaweed (100 mg/kg body-weight) extracts for sixteen weeks. At the end of the experiment all animals were overnight fasted then sacrificed and blood and liver tissues were collected. Results: AOM treatment significantly decreased serum liver markers and induced hepatic oxidative stress as evidenced by increased liver tissue homogenate levels of nitric oxide and malondialdehyde, decreased total antioxidant capacity and glutathione, and inhibition of antioxidant enzymes (catalase, glutathione peroxidase, glutathione S-transferase, glutathione reductase and superoxide dismutase). Both red seaweed extracts abolished the AOM-associated oxidative stress and protected against liver injury as evidenced by increased serum levels of liver function markers. In addition, histological findings confirmed protective effects of the two red seaweed extracts against AOM-induced liver injury. Conclusion: Our findings indicate that red seaweed (Hypnea Bryodies and Melanothamnus Somalensis) extracts counteracted oxidative stress-induced hepatotoxicity in a rat model of colon cancer.