Plasma Transaminase Activities Research Articles

Biochemical and morphological changes in carp ( Cyprinus carpio L.) liver following exposure to copper sulfate and tannic acid

As a consequence of human activity various toxicants reach the aquatic ecosystems; humics may interact with them and may change their toxicity. Many fish are exposed to a considerable concentration of humics and pollutants. Because of paucity of data on the biochemical action of tannins in the presence of the fungicide CuSO 4 a comparative study was undertaken. The alterations of redox-parameters in carp liver were monitored and tissue necrosis was followed by measuring the plasma transaminase activities and by electron microscopy. Tannic acid, a representative phenolic/humic compound, exerted prooxidant effects in carp, which may be partially due to formation of prooxidant intermediates/end-products via its biotransformation. Alternatively, tannic acid may partially inhibit the antioxidant enzymes of fish. The response to CuSO 4 was more severe. Although tannic acid alone acted as a prooxidant in fish, electron micrographs demonstrated that it reduced the necrotizing effect of copper, which may be due to the complexing activity of tannic acid with the biomolecules of the hepatocytes and to the H 2O 2-degrading activity of tannin–CuSO 4 combination. Our results indicate that the heavy metal-detoxifying capacity of tannin may be significant; however, tannin-exposure alone or combined with metals may be toxic for fish due to enzyme inhibition and oxidative stress induction.

Alcohol-induced sinusoidal endothelial cell dysfunction in the mouse is associated with exacerbated liver apoptosis and can be reversed by caspase inhibition

The purpose of this study was to determine if a correlation exists between alcohol-induced liver sinusoidal endothelial cell (SEC) dysfunction and alcohol-induced augmented liver apoptosis in the mouse. Mice were fed an alcohol-containing liquid diet for 7 weeks. On the last day of feeding, the animals were treated with the pan-caspase inhibitor IDN1529 ( N-[(indole-2-)-alaninyl]-3-amino-4-oxo-fluoropentanoic acid), killed, and plasma amino transferase activity, plasma hyaluronan, liver caspase-3 activity, the frequency of apoptotic nuclei in the liver, liver histology and electron microscopic appearance evaluated. Alcohol feeding significantly increased (2.5-fold) plasma hyaluronan levels, frequency of apoptotic nuclei (20-fold), and caspase-3 activity (1.7-fold), but did not affect plasma amino transferase activity. Transmission electron microscopy revealed that SEC was among the cell types undergoing apoptosis. Livers of alcohol-fed mice displayed marked fat accumulation without necrosis or fibrosis. Treatment of mice with IDN1529 reversed the alcohol effects on plasma hyaluronan levels, liver caspase-3 activity, and frequency of apoptotic nuclei. However, the inhibitor did not prevent fat accumulation in the liver. These data suggest that alcohol-induced exacerbation of apoptosis in the liver, which extends to the SEC, causes functional impairment of the sinusoidal lining and can be reversed by caspase inhibition.

Effect of OP-2507, a prostacyclin analogue, on endotoxin-induced hepatic necrosis in rats after partial hepatectomy

Objective: We assessed the cytoprotective effect and mechanism of action of a prostacyclin analogue, OP-2507, on the massive hepatocytic injuries induced in rats by the administration of lipopolysaccharide (LPS) after 70% hepatectomy. Methods: OP-2507 was injected subcutaneously at 1 of 2 doses (100 μg/kg and 300 μg/kg) 30 minutes before, immediately before, or 10 minutes after LPS administration. Liver function, prothrombin time, and tumor necrosis factor alpha (TNF-α) in the serum as well as hydroxyl radicals in the hepatic tissue were measured serially after LPS administration. Results: Pretreatment with OP-2507 attenuated the increase in plasma TNF-α and hydroxyl radicals in hepatic tissue and the increase in plasma aminotransferase activity; it also improved the survival rate. However, these effects were not observed when OP-2507 was administered immediately before or 10 minutes after LPS administration. Conclusions: These results indicate that OP-2507 prevents hepatic damage induced by LPS administration after 70% hepatectomy when it is given 30 minutes before LPS administration.

Murine Concanavalin A–Induced Hepatitis Is Prevented by Interleukin 12 (IL-12) Antibody and Exacerbated by Exogenous IL-12 Through an Interferon-γ–Dependent Mechanism

Concanavalin A (ConA)-induced hepatitis is a cell-mediated immunoinflammatory condition similar to human autoimmune hepatitis. We investigated the role of interleukin 12 (IL-12) in hepatitis induced in NMRI and C57/BL6 mice by a single injection of ConA. Recombinant murine IL-12 administered 24 hours and 1 hour prior to ConA exacerbated both transaminase activities in plasma and histologic signs of hepatitis. These markers of liver injury were significantly reduced by prophylactic, but not therapeutic treatment with anti–IL-12 monoclonal antibody (mAb). The disease-modulatory effects of IL-12 and anti–IL-12 mAb were associated with profound and reverse modifications of a ConA-induced increase in the circulating levels of IL-4, IL-6, interferon gamma (IFN-γ) and tumor necrosis factor (TNF). Relative to control animals receiving ConA alone, the plasma levels of these cytokines were all augmented in IL-12/ConA-treated mice and diminished in anti–IL-12 mAb/ConA-treated mice. Anti–IFN-γ mAb also impeded the appearance of IL-12/ConA-induced hepatitis. Thus, IL-12–induced production of IFN-γ might play a role in mediating the hepatitis-inducing effect of ConA. However, IL-12p40–deficient C57/BL6 mice were as susceptible as wild-type controls to the hepatitis-inducing effect of ConA.(Hepatology 2000;32:728-733.)

Effect of Black Tea on Lipid Peroxide and Glutathione Levels in Female Rats

The effects of black tea (Camellia sinensis L.) on lipid peroxidation and glutathione (GSH) levels in carbon tetrachloride (CCl4)-treated female Wistar rats were examined. Two control groups and one treatment group were tested. The control groups were fed with a standard diet, while the black tea group was fed the standard diet plus 6% by weight dried black tea leaves. At the end of 2 months, a single dose of CCl4 (1 ml/kg, i.p.) in olive oil was administered to rats in one of the control groups and the black tea group. They were sacrificed after 2 hours. Rats in the other control group were administered olive oil in a similar fashion. Measurements were made of lipid peroxide levels in liver and plasma, glutathione levels in liver, and alanine transaminase (ALT) and aspartate transaminase (AST) activities in plasma. Liver lipid peroxide levels, plasma ALT and AST activities were significantly decreased in the black tea group compared with the CCl4-treated control group, while plasma lipid peroxide levels were not. These results are parallel to those previously found with Wistar male rats. Glutathione levels, however, were not significantly affected, in contrast to the data relating to male rats, either after CCl4 or black tea treatments. The results of our study add to the findings that black tea attenuates CCl4-induced hepatic injury but also indicates the susceptibility of glutathione levels to endocrinological effects.

Effect of black tea on lipid peroxidation in carbon tetrachloride treated male rats.

This study examined the effects of black tea (Camellia sinensis L.) on lipid peroxidation and glutathione levels in carbon tetrachloride (CCl4)-treated male Wistar rats. Three groups of rats formed two control groups and one treatment group. The control groups were fed with a standard diet, while the black tea group were fed the standard diet plus 6% by weight dried black tea leaves. After two months, the rats in the black tea group and in one control group were administered a single dose of CCl4 (1 ml/kg, i.p.) and sacrificed two hours later. Rats in the other control group were administered olive oil in a similar fashion. Lipid peroxide levels in liver and plasma, glutathione (GSH) levels in liver and alanine transaminase (ALT) and aspartate transaminase (AST) activities in plasma were measured. Rats in the black tea group were found to have significantly decreased liver lipid peroxide levels, and ALT and AST activities compared with the rats in the CCl4-treated control group. In addition, liver glutathione levels were decreased in the black tea group. These data suggest that black tea attenuates CCl4-induced hepatic injury.

Enhanced monocyte activation and hepatotoxicity in response to endotoxin in portal hypertension

Background/Aims: Septic shock is a systemic response to infection, and it causes a high mortality rate in cirrhotic patients. The mechanisms responsible for this susceptibility in cirrhosis are poorly understood. The aim of this study was to investigate whether monocyte activation and hepatic function are altered in portal hypertension after endotoxin administration. Methods: Portal-hypertensive and sham-operated rats were used. Plasma levels of tumor necrosis factor-α after lipopolysaccharide stimulation (both in vivo and in vitro) were measured by ELISA. CD11b/CD18 integrin expression on leukocyte membrane was measured by flow cytometry. Plasma transaminase activities were also determined. Results: The levels of tumor necrosis factor-α in plasma and the expression of CD11b/CD18 on leukocytes in portal-hypertensive rats was similar to that in sham-operated rats. Injection of 150 μg/kg of lipopolysaccharide produced a 9-fold increase in plasma levels of tumor necrosis factor-α in portal-hypertensive compared with sham-operated rats, together with a significant up-regulation of CD11b/CD18 expression on monocytes and an elevation in plasma transaminase activity. Blood leukocytes incubated in vitro with lipopolysaccharide (0.5 μg/ml) induced a hypersecretion of tumor necrosis factor-α in portal-hypertensive rats, as compared to sham-operated rats. Conclusions: This study shows that monocytes from portal-hypertensive rats have an enhanced response to endotoxin, leading to hepatotoxicity.

The protective effect of glycyrrhizin on anti-Fas antibody-induced hepatitis in mice

Fas ligand, which is a type II membrane protein, is a major inducer of apoptosis. The effect of glycyrrhizin on anti-Fas antibody-induced hepatitis in mice was studied. Pretreatment of mice with glycyrrhizin (100, 200 and 400 mg/kg, i.p.) inhibited the anti-Fas antibody (150 μg/kg, i.v.)-induced elevation of plasma aminotransferase activity in a dose-dependent manner. CPP32 is a cystein protease and CPP32-like activity induced by anti-Fas antibody injection was inhibited by glycyrrhizin (200 mg/kg). However, the addition of glycyrrhizin (up to 10 −4 M) to a liver cytosol fraction isolated from mice treated with anti-Fas antibodies (150 μg/kg, i.v.) did not inhibit the CPP32-like activity in vitro. The present results clearly show that glycyrrhizin inhibited anti-Fas antibody-induced hepatitis by acting upstream of CPP32-like protease activation.

Long lasting chronic hepatitis is accompanied by cyclin D1 gene expression in the mouse.

The interferon-gamma (IFN-gamma) transgenic mouse expresses the IFN-gamma gene strongly in the liver and develops chronic hepatitis from 6-10 weeks of age. Previously we reported the detection of hepatocyte apoptosis and the expression of the Fas system in the transgenic mouse liver. The objective of the present study was to examine the possible development of favorable conditions for predisposing cells to malignancy. The connection between the cell cycle and cancer has become evident, and the relation of cyclin D1 (CD1) with hepatocellular carcinomas has been strengthened. In the liver of transgenic mice of 48 weeks of age, c-myc and CD1 gene expression was induced, indicating progression of the cell cycles. p21 gene expression in the transgenic mouse liver might counteract cell-cycle progression promoted by c-myc and CD1. In the liver of 8-week-old transgenic mice, expression of c-myc mRNA was correlated with the levels of plasma transaminase activities. In these 8-week-old transgenic mice, however, CD1 mRNA was not induced, regardless of the progression of hepatitis. Based on these results, we conclude that long lasting hepatitis may lead to favorable conditions for predisposing cells to malignancy.

Glycyrrhizin protects mice from concanavalin A-induced hepatitis without affecting cytokine expression.

The administration of concanavalin A (Con A) to mice induces cytokine-dependent hepatitis. In the present study, the effect of glycyrrhizin on Con A-induced hepatitis was examined. Treatment of mice with Con A (0.2 mg/mouse, i.v.) induced elevation of the plasma transaminase activities at 24 h. Mice were treated with glycyrrhizin (100, 200 and 400 mg/kg, i.p.), and glycyrrhizin at the doses of 200 and 400 mg/kg inhibited the Con A-induced elevation of the plasma transaminase activities. At 1 h after Con A treatment, interferon-gamma, tumor necrosis factor-alpha, interleukin-2 and interleukin-6 proteins were released into the plasma. Although treatment with glycyrrhizin at 200 mg/kg inhibited Con A-induced hepatitis, it did not affect the release of any of these Con A-induced cytokines into the plasma. The present results clearly show that glycyrrhizin inhibited Con A-induced hepatitis without affecting cytokine expression.

Protection by a cyclic AMP-specific phosphodiesterase inhibitor, rolipram, and dibutyryl cyclic AMP against Propionibacterium acnes and lipopolysaccharide-induced mouse hepatitis.

To study the effect of cellular cAMP-increasing agents on Propionibacterium acnes (P. acnes) and lipopolysaccharide (LPS)-induced mouse hepatitis. Male BALB/c mice were used. Macrophages/Kupffer cells isolated from P. acnes-primed murine liver were used for the in vitro study. Type IV phosphodiesterase (PDE)-specific inhibitor, rolipram, was administered (10, 30 mg/kg, p. o.). Dibutyryl cyclic AMP (dbcAMP) was injected (10, 100 mg/kg, i.p.) into the mice. Plasma TNFalpha estimated by the use of an L-929 cell cytotoxic assay and plasma transaminase activities were measured for the in vivo study. The LPS-induced production of TNFalpha in vitro from the cultured macrophage/Kupffer cells was determined by ELISA. Rolipram suppressed the elevation of plasma transaminases induced by injection of LPS, and dbcAMP had a tendency to suppress them. Both agents attenuated the LPS-induced release of TNFalpha in vivo, and suppressed the TNFalpha production from the cultured macrophage/Kupffer cells. These results suggest that rolipram and dbcAMP have potential to inhibit TNFalpha production from activated macrophage/Kupffer cells, and it may be partially involved in the protecting effect in the P. acnes/LPS hepatitis model.

Concanavalin A-induced Hepatitis in Mice is Prevented by Interleukin (IL)-10 and Exacerbated by Endogenous IL-10 Deficiency

One single intra-venous (i.v.) injection of Concanavalin A (Con A) into mice provokes a cell-mediated immunoinflammatory hepatitis. We have presently evaluated the immunopharma-cological effects of exogenous interleukin (IL)-10 and the role of endogenous IL-10 in this model by using exogenous IL-10, anti-IL-10 monoclonal antibody (mAb) and mice with disrupted IL-10 gene (IL-10 KO mice). Whilst exogenous IL-10 administered in a prophylactic (lh prior to Con A) and even “early” therapeutic fashion (30min after Con A) reduced the elevation of transaminase activities in plasma in a dose-dependent manner, observed in control mice, these biochemical markers of liver injury were significantly increased both in IL-10 KO mice as well as in those receiving anti-IL-10 mAb. Interestingly, doses of Con A lower than 20 mg/kg that were only capable of inducing slight serological signs of hepatitis in mice, exerted marked hepatitic effects when administered to either anti-IL-10 mAb-treated mice or to IL-10 KO mice. The disease modulating effects of exogenous IL-10 and either genetical or pharmacologically-induced IL-10 deficiency were associated with profound and opposite modifications of the Con A-induced increase in the circulating levels of IFN-y and TNF-a. Relative to control animals, the blood levels of these cytokines were diminished in IL-10-treated mice and augmented in both IL-10 KO mice and anti-IL-10 mAb-treated mice. These results prove the physiological antiinflammatory role of endogenous IL-10 in Con A induced hepatitis and the beneficial effects of IL-10 treatment to prevent this condition.

Thioureas differentially induce rat hepatic microsomal epoxide hydrolase and rGSTA2 irrespective of their oxygen radical scavenging effect: effects on toxicant-induced liver injury

Thioureas have been employed as potent hydroxyl radical scavengers and also inhibit production of oxygen free radicals. The in vitro oxygen radical scavenging effect by N, N′-substituted thioureas including dimethylthiourea (DMT), diethylthiourea (DET), tetramethylthiourea (TMT) and diphenylthiourea (DPT) was assessed by the conversion of φx-174 DNA from supercoiled DNA to the open circular form or to fragmented DNA. Addition of the N, N′-substituted thioureas to the incubation mixture significantly prevented a single strand breakage of φx-174 DNA induced by autooxidation of benzenetriol. These thioureas were also effective in preventing degradation of φx-174 DNA induced by autooxidation of benzenetriol in the presence of ferrous iron. In view of the in vitro radical scavenging effect by the thioureas and the role of reactive oxygen species in the induction of phase II detoxifying enzymes, expression of microsomal epoxide hydrolase (mEH) and rGSTA2 in response to these agents was investigated in the rat liver. Rats treated with each of the alkylthioureas exhibited marked increases of mEH and rGSTA2 mRNA levels with TMT being the most effective. DPT an arylthiourea, however, was minimally active in increasing the mRNAs. Time-course studies revealed that DMT, DET and TMT increased the mRNA levels to the greatest extent at 24 h after a single dose of treatment. The levels of mEH and rGSTA2 mRNA were elevated in a dose-dependent manner by the alkylthioureas. Immunoblot analysis showed that the alkylthioureas induced mEH and rGSTA2 proteins in the liver (0.6 mmol/kg per day, 3 days), which was consistent with the increases in the mRNA levels. DMT, DET or TMT enhanced CCl 4-induced liver toxicity, as monitored by plasma aminotransferase activity, although each of the agents alone caused only slight increase in the alanine aminotransferase activity. In contrast to the effects of the alkylthioureas, DPT protected the liver against the toxicant-induced injury. All of the thioureas prevented decreases in the hepatic glutathione level by CCl 4. Expression of cytochrome P450 2E1 and P450 2B1/2, which are implicated with metabolic activation of CCl 4, was assessed after treatment with the thioureas. P450 2E1 and P450 2B1/2 were differentially induced by the alkylthioureas with the expression of P450 2E1 being inversely related with that of P450 2B1/2. These results showed that N, N′-substituted alkylthioureas were capable of inducing mEH and rGSTA2 in the liver with elevation of the mRNAs, that induction of mEH and rGSTA2 by these alkylthioureas might be mediated by production of the reactive oxygens derived from metabolic activation of the agents irrespective of their radical scavenging effect and that the agents rather enhanced toxicant-induced liver injury with the induction of P450 2E1 or P450 2B1/2.

Toxicity evaluation of pharmaceuticals and mechanisms of their effects

Preclinical studies are defined as experiments other than clinical trials that are conducted in test systems under laboratory conditions for determining the safety of test materials for anticipated human use. It is known that preclinical studies are an indispensable requisite for but constitute time/resource-consuming processes in research and development of new pharmaceuticals. Therefore, they must be designed and conducted in a manner to satisfy the criteria that the obtained data are mutually acceptable among various countries to avoid unnecessary duplication of testing. The purpose of the International Conference on Harmonisation (ICH) has been directed towards the resolution of this issue. Major scientific issues in preclinical studies comprise the interpretation of test data with respect to prediction of potential adverse effects of a test material in humans. Mechanistic consideration of the toxic effects occurring in animals given a test material can usually provide a scientific basis for evaluating the potential hazard of the material in humans. For example, when a test material was found to exhibit a carcinogenic effect in a long-term animal test, one will attempt to determine, on the basis of data from genotoxicity studies, repeated dose toxicity tests, toxicokinetic studies or pharmacology studies on the substance, whether the carcinogenic effect is due to its genotoxicity (genotoxic carcinogen) or a sequela of some secondary mechanisms (non-genotoxic carcinogen). In the cases where a test material was shown to exert toxic effects with either functional manifestation or non-neoplastic morphological manifestation, elucidation of the mechanism will also be useful for extrapolation of animal data to the human situation. It is known that pharmaceuticals induce their toxic effects through various mechanisms such as covalent binding of active intermediates with macrolecules of target cells, oxidative stress-mediated effects, hormone-mediated effects or cytokinemediated effects. As shown in hepatocarcinogenesis or elevation of plasma transaminase activities in rodents attributable to activation of PPAR-alpha, nuclear receptors or ligand-dependent transcription factors are, now, regarded as important targets for toxicity evaluation of pharmaceuticals.

Acute Hepatotoxicity ofPseudomonas aeruginosaExotoxin A in Mice Depends on T Cells and TNF

AbstractThe most potent virulence factor of Pseudomonas aeruginosa, its exotoxin A (PEA), inhibits protein synthesis, especially in the liver, and is a weak T cell mitogen. This study was performed to correlate hepatotoxic and possible immunostimulatory features of PEA in vivo. Injection of PEA to mice caused hepatocyte apoptosis, an increase in plasma transaminase activities, and the release of TNF, IFN-γ, IL-2, and IL-6 into the circulation. Most strikingly, liver damage depended on T cells. Athymic nude mice or mice depleted of T cells by anti-Thy1.2 mAb pretreatment failed to develop acute hepatic failure, and survival was significantly prolonged following T cell depletion. Neutralization of TNF or lack of TNF receptors prevented liver injury. In the liver, TNF was produced by Kupffer cells before hepatocellular death occurred. After T cell depletion, Kupffer cells failed to produce TNF. Transaminase release was significantly reduced in perforin knockout mice, and it was even elevated in lpr/lpr mice. These results demonstrate that PEA induces liver damage not only by protein synthesis inhibition but also by TNF- and perforin-dependent, Fas-independent, apoptotic signals.

Hepatitis C virus infection-associated non-cryoglobulinaemic monoclonal IgMκ gammopathy responsive to interferon-α treatment

Background/Aims: An association of HCV infection with lymphoproliferative disorders, particularly B-cell non-Hodgkin's lymphoma has been described. In the majority of reported patients, mixed cryoglobulinaemia was present as well. Rarely, HCV-associated lymphoproliferative disorders have been observed in the absence of cryoglobulinaemia. In these latter patients, the response to interferon-α is largely unknown. Case Report: We report a case of an asymptomatic 31-year-old male with chronic HCV infection and non-cryoglobulinaemic monoclonal IgMκ gammopathy responsive to interferon-α therapy. Prior to therapy, elevated plasma transaminase activities known for longer than a year, serum anti-HCV antibodies and HCV RNA detected by reverse transcriptase-polymerase chain reaction were presnet. Serum IgM concentration was markedly elevated, immunofixation demonstrated monoclonal serum IgM, and urine κ-light chains were detected. Cryoglobulins were undetectable in several consecutive serum samples. Bone marrow aspirate and biopsy specimens were unremarkable. Further evaluation, e.g. by ultrasonography and radiography, did not reveal evidence for lymphoma. Treatment with interferon-α 2a for 12 months resulted in a long-term sustained response to HCV infection and in a normalisation of serum IgM concentration. Conclusion: Therefore, the corresponding effects of interferon-α on HCV infection and on a monoclonal B-cell population observed in the present case might suggest a pathogenetic connection, similarly, to what has been described for HCV and mixed cryoglobulinaemia. The molecular events, however, leading to HCV-induced monoclonal B-cell expansion remain unknown.

Potentiation of acetaminophen hepatotoxicity and mortality by doxapram in mice.

Whether a single dose of doxapram (DOP) can modulate the acute toxicity and the hepatotoxicity induced by acetaminophen (AA) was examined. Pretreatment with DOP (40 mg/kg, i.p.) 30 min prior to the administration of AA dose-dependently potentiated the lethality of AA in both native mice and mice fasted for 18 h, and the potentiating activity was greater in fasted mice than in native mice. The hepatotoxicity of AA was assessed by plasma transaminases activity (glutamyl oxaloacetic transaminase, GOT; glutamyl pyruvic transaminase, GPT) and the amount of plasma lipid peroxides at 6, 12, 18, 24, 36 and 48h after the administration of AA and histopathological examination of liver sections at 24 h after the administration of AA. DOP (40 mg/kg, i.p.) did not increase the plasma transaminase activity or the lipid peroxides level significantly, whereas AA administration to DOP-treated animals produced earlier maximal elevation of transaminase and lipid peroxide values compared to AA alone. These findings indicate that mortality and hepatotoxicity of AA is potentiated by DOP in mice.

Whole-body urea cycling and protein turnover during hyperphagia and dormancy in growing bears (Ursus americanusandU.arctos)

Subadult bears were studied during their autumn hyperphagia (n = 3) and winter dormancy (n = 6). Urea kinetics were measured with14C- and15N-urea, protein turnover was estimated with15N-glycine, and body composition was assessed with3H-water. Reduced amino acid degradation in winter was indicated by declines in plasma urea and aminotransferase activities, and lower urea production than in autumn (4.7 vs. 27.5 mmol urea-N∙kg−0.75∙d−1). Only 7.5% of urea produced in hyperphagic bears was degraded and just 1.1% of the degraded N reutilized as amino-N. Dormant bears reutilized 99.7% of urea produced, indicating thorough microbial ureolysis and urea-N resorption. Low rates of body N loss during dormancy suggested losses of non-urea N as creatinine. Protein turnover rates (15.2–21.5 g∙kg−0.75∙d−1) were similar between seasons and reflected the apparent maintenance of hepatic, intestinal, and muscular functions through dormancy. Protein synthesis accounted for 32% of energy expended in dormancy, which was mainly (91.5%) derived from fat oxidation. Consistent organ function and body temperature in dormant bears enables recycling of urea-N, which minimizes body protein loss and conserves mobility. In comparison with heterothermic hibernation, ursid dormancy would provide greater flexibility during winter and facilitate rapid resumption of foraging and growth in spring.

Metallothionein-independent hepatoprotection by zinc and sakuraso-saponin

Hepatoprotective activities of zinc and sakuraso-saponin against toxicity of carbon tetrachloride were investigated in metallothionein (MT)-deficient mice. Pretreatment of control 129/Sv mice with zinc or sakuraso-saponin blocked carbon tetrachloride-induced elevation of plasma transaminase activities. Quantitatively equivalent protection against carbon tetrachloride-induced hepatic damage was also observed in MT-deficient mice. Zinc and sakuraso-saponin caused elevation of hepatic MT levels in control 129/Sv mice, whereas hepatic MT was undetectable in MT-deficient mice. To examine the possibility that sakuraso-saponin-induced hepatoprotection is mediated by endogenous zinc, the hepatic concentration of zinc was analyzed. Hepatic zinc concentration in MT-deficient mice was not changed by the treatment of sakuraso-saponin. Injection of sakuraso-saponin caused a decrease of activity of aniline hydroxylation. The suppression of cytochrome P450 appears to be a mechanism by which sakuraso-saponin protects mice from the hepatotoxic effects of carbon tetrachloride. These findings indicate that the hepatoprotective activity of zinc or sakuraso-saponin is not dependent on their MT-inducing activity.

Ethanol feeding enhances inflammatory cytokine expression in lipopolysaccharide-induced hepatitis.

Elevated concentrations of plasma tumour necrosis factor (TNF)-alpha, interleukin (IL)-1 and IL-6 have been detected in patients with alcoholic hepatitis and have been implicated in the pathogenesis of hepatocyte necrosis. The present study used a rat model to conduct a detailed histological and biochemical examination of the expression of various pro-inflammatory cytokines and associated liver pathology in ethanol-potentiated lipopolysaccharide (LPS)-induced liver injury. Male Wistar rats were pair-fed either the control or ethanol-containing (36% of caloric intake as ethanol) form of the Lieber-DeCarli liquid diet for 6 weeks. Liver injury was induced by the i.v. injection of LPS (1 microgram/g bodyweight), with animals being killed at 0, 1, 3, 6, 12 and 24 h after injection. At the later time points, plasma transaminase and transpeptidase activities were significantly elevated in ethanol-fed LPS-treated rats compared with control-fed LPS-treated animals. At these times after LPS treatment, hepatocytes in ethanol-fed animals displayed fatty change and necrosis with an associated neutrophil polymorph infiltrate. Time course analysis revealed that plasma TNF-alpha (1-3 h post-LPS) and IL-6 (3 h post-LPS) bioactivity was significantly elevated in ethanol-fed compared with control-fed animals. No difference was seen in plasma IL-1 alpha concentration (maximal in both groups 6 h post-LPS). The expression of TNF-alpha, IL-1 alpha, IL-1 beta and IL-6 mRNA were elevated between 1 and 6 h post-LPS in the livers of both control and ethanol-fed rats. However, ethanol-fed LPS-treated animals exhibited significantly higher maximal expression of IL-1 and IL-6 mRNA. Comparison of the appearance of cytokine mRNA and plasma bioactivity indicated an effect of ethanol feeding on post-transcriptional processing and/or the kinetics of the circulating cytokines. Elevated levels of both hepatic cytokine mRNA expression and the preceding plasma cytokines are presumably a necessary prerequisite for hepatic injury seen in this model and, therefore, possibly for the damage seen in human alcoholics. Further studies using this model may lead to significant advances in our understanding of the pathogenic mechanisms of alcoholic liver disease in humans.