Hepatic Reduced Glutathione Levels Research Articles

The effect of Alnus incana (L.) Moench extracts in ameliorating iron overload-induced hepatotoxicity in male albino rats

Iron overload causes multiorgan dysfunction and serious damage. Alnus incana from the family Betulaceae, widely distributed in North America, is used for treating diseases. In this study, we investigated the iron chelating, antioxidant, anti-inflammatory, and antiapoptotic activities of the total and butanol extract from Alnus incana in iron-overloaded rats and identified the bioactive components in both extracts using liquid chromatography-mass spectrometry. We induced iron overload in the rats via six intramuscular injections of 12.5 mg iron dextran/100 g body weight for 30 days. The rats were then administered 60 mg ferrous sulfate /kg body weight once daily using a gastric tube. The total and butanol extracts were given orally, and the reference drug (deferoxamine) was administered subcutaneously for another month. After two months, we evaluated the biochemical, histopathological, histochemical, and immunohistochemical parameters. Iron overload significantly increased the serum iron level, liver biomarker activities, hepatic iron content, malondialdehyde, tumor necrosis factor-alpha, and caspase-3 levels. It also substantially (P < 0.05) reduced serum albumin, total protein, and total bilirubin content, and hepatic reduced glutathione levels. It caused severe histopathological alterations compared to the control rats, which were markedly (P < 0.05) ameliorated after treatment. The total extract exhibited significantly higher anti-inflammatory and antiapoptotic activities but lower antioxidant and iron-chelating activities than the butanol extract. Several polyphenolic compounds, including flavonoids and phenolic acids, were detected by ultraperformance liquid chromatography-electrospray ionization-quadrupole time-of-flight mass spectrometry (UPLC-ESI-QTOF-MS) analysis. Our findings suggest that both extracts might alleviate iron overload-induced hepatoxicity and other pathological conditions characterized by hepatic iron overload, including thalassemia and sickle-cell anemia.

Moringa oleifera alleviated oxidative stress, physiological and molecular disruption induced by acute thermal stress in grass carp, Ctenopharyngodon idella.

The present study was designed to investigate the protective effect of dietary Moringa oleifera leaf meal (MLM) supplementation against high temperature-induced stress in grass carp (Ctenopharyngodon idella). A total of 180 apparent healthy juvenile grass carp (15.48g ± 0.054) were divided into three groups in triplicate (20 fish in each replicate). Fish were fed with diets containing 0, 1, and 5% MLM for 60days and then subjected to a high-temperature challenge for 48h (32-33°C). The results revealed that feeding fish with 1 and 5% MLM resulted in a significant increase in weight gain and specific growth rate compared to the control. In addition, feed conversion ratio was significantly reduced in groups fed with MLM. No significant difference was reported in the serum cortisol level among different experimental groups before heat stress while serum glucose level significantly decreased in fish fed with 5% MLM. Serum alanine transaminase, aspartate transaminase, and alkaline phosphatase significantly decreased in fish fed with 1 and 5% MLM before and after heat stress. Hepatic lipid peroxidation significantly decreased in fish fed with MLM for 60days. A non-significant increase in hepatic reduced glutathione level was reported in fish fed with 1 and 5% MLM before heat stress. Catalase and superoxide dismutase activities increased significantly in the liver of fish fed with 5% MLM. No significant change was observed in the expression profile of heat shock protein (hsp) 70 and 90 before heat stress. Meanwhile, after heat stress, up to a fivefold increase was recorded in mRNA level of hsp 70 and fourfold increase in the expression level of hsp 90 in the liver of the control fish which were not fed with MLM-supplemented diets. Fish fed with 1 and 5% MLM showed a significant decrease in the expression of hsp 70 and a non-significant decrease in the expression of hsp 90. Results of the present study suggest that supplementing the diet of grass carp with 5% MLM could improve growth and physiological performance and provide resistance against high temperature-induced stress.

Ellagic acid as a potential antioxidant, alleviates methotrexate-induced hepatotoxicity in male rats

Background: Hepatotoxicity is one of the most life-threatening side-effects of Methotrexate therapy. Former studies highlighted the significance of oxidative stress in promoting Methotrexate-induced hepatotoxicity (MIH). Hence, the current study investigated the protective effect of Ellagic acid (EA), a poly-phenolic antioxidant, against MIH.Methods: Twenty-eight male Wistar rats were grouped into four sets: group 1 (control), group 2 (injected intraperitoneally with 20 mg/kg of Methotrexate on the 9th day), group 3 (treated orally with 10 mg/kg/day of EA for 10 days and injected with Methotrexate on the 9th day) and group 4 (treated with EA for 10 days). Subsequently, biochemical and histopathological parameters were evaluated in serum samples and liver tissues.Results: Methotrexate significantly increased activities of aminotransferases and ALP enzymes as well as levels of oxidative stress parameters in liver tissue. Likewise, Methotrexate decreased hepatic reduced glutathione level and activities of antioxidant enzymes. EA pre-treatment markedly attenuated the activities of aminotransferases and ALP, levels of oxidative stress parameters and augmented activities of antioxidant enzymes. Similarly, the remarkable protective effect of EA on liver has been confirmed by histological examination.Conclusion: In sum, the current study supports the hypothesis that EA may be used as a promising pre-therapy to prevent the MIH.

Compound 48/80, a mast cell degranulator, causes oxidative damage by enhancing vitamin C synthesis via reduced glutathione depletion and lipid peroxidation through neutrophil infiltration in rat livers.

In this study, we examined whether compound 48/80 (C48/80), a mast cell degranulator, causes hepatic oxidative damage in rats. Serum and liver biochemical parameters were determined 0.5, 3 or 6 h after a single treatment with C48/80 (0.75 mg/kg). Serum histamine and serotonin levels increased 0.5 h after C48/80 treatment but diminished thereafter. Increases in serum vitamin C (VC) and transaminases and hepatic hydrogen peroxide, lipid peroxide, and myeloperoxidase levels and a decrease in hepatic reduced glutathione level occurred 0.5 h after C48/80 treatment and further proceeded at 3 h, but these changes diminished at 6 h. Serum lipid peroxide and hepatic VC levels increased 3 h after C48/80 treatment. Hepatic glycogen level decreased 0.5 h after C48/80 treatment and further decreased at 3 h. Pre-administered ketotifen diminished all these changes found at 3 h after treatment, while pre-administered NPC 14686 diminished these changes except changes in serum histamine and serotonin levels. Hepatocellular apoptosis observed at 3 h after C48/80 treatment was attenuated by pre-administered ketotifen and NPC 14686. These results indicate that C48/80 causes oxidative damage by enhancing VC synthesis via reduced glutathione depletion-dependent glycogenolysis and lipid peroxidation through neutrophil infiltration following mast cell degranulation in rat livers.

Abstract 132: Biomarkers of Cardiovascular Toxicity Following Benzene Exposure

Benzene is a ubiquitous environmental pollutant abundant in plastics, petroleum products and cigarette smoke. Although hematopoietic and hepatic toxicity of benzene has been extensively studied, little is known about the effect of benzene on cardiovascular health. In this study, we assessed benzene exposure in a cohort of 210 participants with moderate to high CVD risk by measuring urinary benzene metabolite - trans, trans-muconic acid (t,t-MA). After adjusting for confounding variables we observed a 9% decrease in circulating levels of both early (AC133+) and late (AC133-) angiogenic cells for every 0.1mg t,t-MA/g creatinine increase in the urine. Uriniary t,t,MA levels were also positively associated with hyperlipidemia (P&lt;0.02). Although smoking was associated with higher urinary levels of, t,t-MA, the association between benzene exposure and CVD risk was independent of smoking. In non-smokers, t,t-MA levels were positively associated with increased Framingham Risk Scores. Next, we examined the association of surrogate markers of cardiovascular functions and injury in male C57BL/6 mice exposed to HEPA-filtered air or benzene (50 ppm) for 6 hours/day for two (n=34/treatment) or six weeks (n=20/treatment). Both at two and six weeks of exposure to benzene increased fasting plasma glucose (13%, P&lt;0.05), fasting insulin (39%, P&lt;0.05) and HOMA-IR (72%, P&lt;0.05); and platelet-leukocyte aggregates (PLAggs), a marker of platelet activation in vivo. This was accompanied by 26% decrease (P&lt;0.05) in hepatic reduced glutathione level and activation of NF-κB in the liver and skeletal muscle. Moreover, after 6 weeks of benzene exposure plasma LDL and HDL were increased by 25% (P&lt;0.05) and 5% (P&lt;0.05) respectively; circulating endothelial microparticles were increased by 60% (P&lt;0.05); and blood endothelial progenitor cells (EPCs) were decreased by 52% (P&lt;0.05). These data suggest that exposure to benzene is associated with potential deficits in vascular repair and increased CVD risk.

Fucoidan ameliorates steatohepatitis and insulin resistance by suppressing oxidative stress and inflammatory cytokines in experimental non-alcoholic fatty liver disease.

Fucoidan, a sulfated polysaccharide derived from brown seaweeds, possesses a wide range of pharmacological properties. In the present study, we investigated the therapeutic effect of fucoidan on non-alcoholic fatty liver disease (NAFLD) in rats. Rats were fed a high-fat diet (HFD) for 12 weeks to induce NAFLD. Oral administrations of fucoidan (100mg/kg, orally), metformin (200mg/kg, orally) or the vehicle were started in the last four weeks. Results showed that administration of fucoidan for 4 weeks attenuated the development of NAFLD as evidenced by the significant decrease in liver index, serum liver enzymes activities, serum total cholesterol and triglycerides, fasting serum glucose, insulin, insulin resistance, and body composition index. Further, fucoidan decreased hepatic malondialdehyde as well as nitric oxide concentrations, and concomitantly increased hepatic reduced glutathione level. In addition, the effect of fucoidan was accompanied with significant decrease in hepatic mRNA expressions of tumor necrosis factor-α, interleukins-1β and matrix metalloproteinase-2. Furthermore, histopathological examination confirmed the effect of fucoidan. In conclusion, fucoidan ameliorated the development of HFD-induced NAFLD in rats that may be, at least partly, related to its hypolipidemic, insulin sensitizing, antioxidant and anti-inflammatory mechanisms.

Effect of homopterocarpin, an isoflavonoid from Pterocarpus erinaceus, on indices of liver injury and oxidative stress in acetaminophen-provoked hepatotoxicity

Novel hepatoprotectives are needed to address the increasing cases of liver problems worldwide. Pterocarpus erinaceus Poir (Fabaceae) ethanol stem bark extract (PE) and its constituent flavonoid, homopterocarpin (HP), were investigated for their protective property in acetaminophen-induced oxidative stress and liver damage. Adult male albino rats were divided into nine groups. Seven groups were pretreated with PE (50-, 100-, and 150 mg/kg), HP (25-, 50-, and 75 mg/kg) or silymarin (25 mg/kg), respectively, once daily for 5 consecutive days and then administered acetaminophen (2 g/kg) on the 5th day. The control and acetaminophen-intoxicated groups received normal saline throughout the experimental period, with the latter group additionally receiving 2 g/kg acetaminophen on the 5th day. Administrations were performed po. In the acetaminophen-intoxicated group, there were significant increases (p<0.05) in serum activities of alanine aminotransferase (31.72±3.3 vs. 22.1±1.2 U/I), aspartate aminotransferase (185.1±10.1 vs. 103.83±13.3 U/I), bilirubin level and hepatic malondialdehyde (2.32±0.3 vs. 1.42±0.1 units/mg protein), accompanied with significant decreases (p<0.05) in hepatic reduced glutathione level (0.10±0.01 vs. 0.23±0.03 units/mg protein) and glutathione peroxidase activity (2.51±0.2 vs. 3.25±0.2 μmol H2O2 consumed/min/mg protein) compared with the control. PE and HP ameliorated most of the observed biochemical alterations with HP appearing to show more potency. The results suggest that the flavonoid, homopterocarpin contributes to the hepatoprotective and antioxidant potentials of P. erinaceus extract.

Severe dysfunction of respiratory chain and cholesterol metabolism in Atp7b −/− mice as a model for Wilson disease

Wilson disease (WD) is caused by mutations of the WD gene ATP7B resulting in copper accumulation in different tissues. WD patients display hepatic and neurological disease with yet poorly understood pathomechanisms. Therefore, we studied age-dependent (3, 6, 47 weeks) biochemical and bioenergetical changes in Atp7b −/− mice focusing on liver and brain. Mutant mice showed strongly elevated copper and iron levels. Age-dependently decreasing hepatic reduced glutathione levels along with increasing oxidized to reduced glutathione ratios in liver and brain of 47 weeks old mice as well as elevated hepatic and cerebral superoxide dismutase activities in 3 weeks old mutant mice highlighted oxidative stress in the investigated tissues. We could not find evidence that amino acid metabolism or beta-oxidation is impaired by deficiency of ATP7B. In contrast, sterol metabolism was severely dysregulated. In brains of 3 week old mice cholesterol, 8-dehydrocholesterol, desmosterol, 7-dehydrocholesterol, and lathosterol were all highly increased. These changes reversed age-dependently resulting in reduced levels of all previously increased sterol metabolites in 47 weeks old mice. A similar pattern of sterol metabolite changes was found in hepatic tissue, though less pronounced. Moreover, mitochondrial energy production was severely affected. Respiratory chain complex I activity was increased in liver and brain of mutant mice, whereas complex II, III, and IV activities were reduced. In addition, aconitase activity was diminished in brains of Atp7b −/− mice. Summarizing, our study reveals oxidative stress along with severe dysfunction of mitochondrial energy production and of sterol metabolism in Atp7b −/− mice shedding new light on the pathogenesis of WD.

Pentoxifylline and melatonin in combination with pioglitazone ameliorate experimental non-alcoholic fatty liver disease

Insulin resistance, oxidative stress and cytokine imbalance are key pathophysiological mechanisms in non-alcoholic fatty liver disease (NAFLD). This study aimed at evaluating the effect of treatment with the insulin sensitizer, pioglitazone, the tumor necrosis factor-α inhibitor, pentoxifylline, and the antioxidant, melatonin and their combinations in rats with NAFLD. Rats were fed a high-fat diet (HFD) for eight weeks to induce NAFLD. For an additional eight weeks, rats were fed the HFD along with pioglitazone, pentoxifylline, melatonin alone or in combination. Liver index and insulin resistance index were calculated. Serum liver enzyme activities, total cholesterol, triglycerides and tumor necrosis factor-α (TNF-α) were determined. Tissue triglycerides, malondialdehyde and reduced glutathione were measured and liver injury was evaluated by histopathological examination. HFD induced severe hepatic steatosis, inflammation and fibrosis. In addition, liver index, insulin resistance index, activities of liver enzymes and serum level of total cholesterol, triglycerides and TNF-α were elevated. This was coupled with an increase in tissue triglycerides, malondialdehyde and depletion of reduced glutathione. Pioglitazone, pentoxifylline and melatonin, alone or in combination; reduced the insulin resistance index, activities of liver enzymes, hepatic malondialdehyde and increased hepatic reduced glutathione level. Pentoxifylline led to a decrease in serum TNF-α level, however, pioglitazone and melatonin reduced serum total cholesterol and triglycerides. In conclusion, data in this study indicate that pentoxifylline and melatonin can be used as promising adjuvant therapies to pioglitazone in the clinical management of NAFLD.

The crucial protective role of glutathione against tienilic acid hepatotoxicity in rats

To investigate the hepatotoxic potential of tienilic acid in vivo, we administered a single oral dose of tienilic acid to Sprague–Dawley rats and performed general clinicopathological examinations and hepatic gene expression analysis using Affymetrix microarrays. No change in the serum transaminases was noted at up to 1000 mg/kg, although slight elevation of the serum bile acid and bilirubin, and very mild hepatotoxic changes in morphology were observed. In contrast to the marginal clinicopathological changes, marked upregulation of the genes involved in glutathione biosynthesis [glutathione synthetase and glutamate-cysteine ligase (Gcl)], oxidative stress response [heme oxygenase-1 and NAD(P)H dehydrogenase quinone 1] and phase II drug metabolism (glutathione S-transferase and UDP glycosyltransferase 1A6) were noted after 3 or 6 h post-dosing. The hepatic reduced glutathione level decreased at 3–6 h, and then increased at 24 or 48 h, indicating that the upregulation of NF-E2-related factor 2 (Nrf2)-regulated gene and the late increase in hepatic glutathione are protective responses against the oxidative and/or electrophilic stresses caused by tienilic acid. In a subsequent experiment, tienilic acid in combination with l-buthionine-(S,R)-sulfoximine (BSO), an inhibitor of Gcl caused marked elevation of serum alanine aminotransferase (ALT) with extensive centrilobular hepatocyte necrosis, whereas BSO alone showed no hepatotoxicity. The elevation of ALT by this combination was observed at the same dose levels of tienilic acid as the upregulation of the Nrf2-regulated genes by tienilic acid alone. In conclusion, these results suggest that the impairment of glutathione biosynthesis may play a critical role in the development of tienilic acid hepatotoxicity through extensive oxidative and/or electrophilic stresses.

Effects of acute and subchronic exposures to waterborne selenite on the physiological stress response and oxidative stress indicators in juvenile rainbow trout

Selenium (Se) is an essential element that may bioaccumulate to toxic levels. In fish, the major toxicity symptom is larval teratogenic deformities, but little is known about the effect of Se on other systems such as the physiological stress response and oxidative stress. To test the hypothesis that Se is a chemical stressor that causes toxicity through oxidative stress, juvenile rainbow trout were exposed to waterborne sodium selenite, and physiological stress response and stress-related parameters (plasma cortisol, glucose, T3 and T4, gill Na +/K +-ATPase, the ability of the head kidney to secrete cortisol, and condition factor) and hepatic oxidative stress indicators (reduced glutathione, glutathione peroxidase, and lipid peroxidation) were measured after 96 h (acute exposure to 0–2.67 mg/L Se) and 30 days (sub-chronic exposure to 0–0.16 mg/L). Acute exposure to waterborne sodium selenite significantly increased plasma cortisol levels (control = 0.01 ± 0.0 ng/mL, and 2.52 mg/L Se = 73.5 ± 22 ng/mL) and plasma glucose levels (control = 0.75 ± 0.1 mg/mL, and 3.60 mg/L Se = 1.64 ± 0.2 mg/mL), but gill Na +/K +-ATPase activities, plasma T3 and T4 levels, and condition factor were unchanged. The 96 h acute selenite exposure decreased hepatic reduced glutathione levels (control = 18.4 ± 1.5 μmol/mg protein, and 3.60 mg/L Se = 12.4 ± 1.1 μmol/mg protein). Lipid peroxidation levels (0.03–0.08 U/mg protein) and glutathione peroxidase (3.7–6.0 mU/mg protein) activities significantly varied with treatment. The 30 days sub-chronic exposure increased plasma cortisol, T3, and T4, but there was no effect on plasma glucose levels, gill Na +/K +-ATPase activity, the ability to secrete cortisol, and condition factor. The 30 days sub-chronic exposure to selenite did not alter antioxidant activities or lipid peroxidation levels. These experiments show, for the first time, that exposure to waterborne selenite up to 0.1 mg/L, activates the physiological stress response in fish but does not impair cortisol secretion after 30 days. The decrease in reduced glutathione in juvenile rainbow trout subjected to the acute sodium selenite exposure suggests that oxidative stress may play an important role in the effects of Se in fish.

Protective effect of Platycodi radix on carbon tetrachloride-induced hepatotoxicity

The protective effects of a Platycodi radix (Changkil: CK), the root of Platycodon grandiflorum A. DC ( Campanulaceae) on carbon tetrachloride (CC1 4)-induced hepatotoxicity and the possible mechanisms involved in this protection were investigated in mice. Pretreatment with CK prior to the administration of CC1 4 significantly prevented the increased serum enzymatic activities of alanine and aspartate aminotransferase in a dose-dependent manner. In addition, pretreatment with CK also significantly prevented the elevation of hepatic malondialdehyde formation and the depletion of reduced glutathione content in the liver of CC1 4-intoxicated mice. However, hepatic reduced glutathione levels and glutathione S-transferase activities were not affected by treatment with CK alone. CC1 4-induced hepatotoxicity was also essentially prevented, as indicated by a liver histopathologic study. The effects of CK on the cytochrome P450 (P450) 2E1, the major isozyme involved in CC1 4 bioactivation were also investigated. Treatment of mice with CK resulted in a significant decrease of P450 2E1-dependent p-nitrophenol and aniline hydroxylation in a dose-dependent manner. CK showed antioxidant effects in FeCl 2–ascorbate-induced lipid peroxidation in mice liver homogenate and in superoxide radical scavenging activity. Our results suggest that the protective effects of CK against CC1 4-induced hepatotoxicity possibly involve mechanisms related to its ability to block P450-mediated CC1 4 bioactivation and free radical scavenging effects.

Protective effect of ajoene on acetaminophen-induced hepatic injury in mice.

Ajoene, a garlic-derived sulfur-containing compound, exhibited a hepatoprotective effect against acetaminophen-induced liver injury in mice. A pretreatment with ajoene suppressed the rise in serum glutamic-pyruvic transaminase activity and the reduction in the hepatic reduced glutathione level. These effects of ajoene were observed dose-dependently (20-100 mg/kg). The pretreatment by ajoene also suppressed the decrease in hepatic protein thiol content resulting from acetaminophen administration.

Mechanisms of Protection by S-Allylmercaptocysteine Against Acetaminophen-Induced Liver Injury in Mice

S-Allylmercaptocysteine (SAMC), one of the water-soluble organosulfur compounds in ethanol extracts of garlic (Allium sativum L.), has been shown to protect mice against acetaminophen (APAP)-induced liver injury. In this study, we examined the mechanisms underlying this hepatoprotection. SAMC (100 mg/kg, p.o.) given 2 and 24 hr before APAP administration (500 mg/kg, p.o.) suppressed the plasma alanine aminotransferase activity increases 3 to 12 hr after APAP administration significantly. The hepatic reduced glutathione levels of vehicle-pretreated mice decreased 1 to 6 hr after APAP administration, but SAMC pretreatment suppressed the reductions 1 to 6 hr after APAP administration significantly. These inhibitory effects of SAMC were dose-dependent (50–200 mg/kg) 6 hr after APAP administration. As SAMC pretreatment (50–200 mg/kg) suppressed hepatic cytochrome P450 2E1-dependent N-nitroso-dimethylamine demethylase activity significantly in a dose-dependent manner, we suggest that one of its protective mechanisms is inhibition of cytochrome P450 2E1 activity. SAMC pretreatment also suppressed the increase in hepatic lipid peroxidation and the decrease in hepatic reduced coenzyme Q9 (CoQ9H2) levels 6 hr after APAP administration. The hepatic CoQ9H2 content of the SAMC pretreatment group was maintained at the normal level. Therefore, we suggest that another hepatoprotective mechanism of SAMC may be attributable to its antioxidant activity.

Prevention of Naphthalene-Induced Cataract and Hepatic Glutathione Loss by the L-Cysteine Prodrugs, MTCA and PTCA

Rapid-onset cataracts were induced in SPF C57 bl/6 mice by intraperitoneal administration of naphthalene following cytochrome P-450 isozyme induction with phenobarbital. Several l-cysteine prodrugs with masked sulfhydryl groups in the form of thiazolidine-4-carboxylic acids, as well as N-acetyl- l-cysteine, N,S- bis-acetyl- l-cysteine and glutathione ethyl ester, were evaluated for their ability to maintain hepatic and lenticular glutathione at near-normal levels and to prevent naphthalene-induced cataract formation. Each prodrug was administered at three specified times to a cumulative total of 1.5 mole equivalents of the single dose of naphthalene. Three l-cysteine prodrugs delayed but did not prevent cataract formation in 40–60% of the mice over a 72-hr period, while eight of the 13 compounds produced cataract yields similar to the naphthalene control animals, i.e. 83% in 72hr. However, two l-cysteine prodrugs, 2( R,S)-methylthiazolidine-4( R)-carboxylic acid (MTCA) and 2( R,S)- n-propylthiazolidine-4( R)-carboxylic acid (PTCA), prevented cataract formation in 20 of 21 and 12 of 12 mice, respectively, and maintained hepatic reduced glutathione levels at 82% and 51% of untreated controls. In contrast, glutathione was depressed to 3% of the normal value in those animals treated with naphthalene alone. Lenticular glutathione values were depressed, albeit minimally, in all naphthalene-treated mice regardless of administration of either MTCA or PTCA. The mice protected with either MTCA or PTCA showed no visible effects of naphthalene toxicity or lens opacities at any time. It can be concluded that these l-cysteine prodrugs were effective in preventing naphthalene-induced cataract and maintaining near-normal hepatic glutathione levels.

Comparison of the effects of ascorbyl palmitate and L-ascorbic acid on paracetamol-induced hepatotoxicity in the mouse

The effects of ascorbyl palmitate (ASCP) and free L-ascorbic acid (LAA) on the hepatotoxicity of paracetamol (acetaminophen) and the in vivo covalent binding of reactive paracetamol metabolites to hepatic proteins has been studied in male MF1 mice. The oral administration of [ 3H(G)]paracetamol (600 mg/kg) resulted in covalent binding to hepatic proteins, a depletion of hepatic non-protein sulphydryl (NPS) groups after 2 h, and a marked elevation of plasma alanine aminotransferase (ALAT) activity after 24 h. The coadministration of paracetamol and ASCP (1412 mg/kg), equivalent to 600 mg/ kg free LAA), but not paracetamol and LAA (600 mg/kg), significantly reduced covalent binding of paracetamol metabolites at 2 and 4 h after treatment. In addition ASCP, but not LAA, significantly reduced the depletion of NPS groups and the elevation of plasma ALAT activity. ASCP also completely prevented the 35% mortality observed at 24 h in paracetamol treated mice. These results demonstrate that ASCP, but not LAA, when coadministered orally with the analgesic is an effective inhibitor of paracetamol-induced hepatotoxicity in the mouse. The mechanism by which ASCP prevents liver injury appears to involve destruction of reactive paracetamol metabolites which is associated with a sparing action on hepatic reduced glutathione levels.

Loss of hepatic monooxygenase activities, glutathione, and ‘green pigment’ formation after the administration of vinyl-cyclooctane to mice

Vinylcyclooctane, when administered to mice at 500 mg/kg, produced reduction of microsomal cytochrome P-450, heme, aminopyrine- N-demethylase and ethoxycoumarin- O-deethylase activities with respect to control values; furthermore the hepatic reduced glutathione level was depleted suggesting that glutathione is involved in the vinylcyclooctane metabolism. The reduction of cytochrome P-450 and monooxygenase activities was accompanied by the formation of abnormal ‘green pigments’.

Effects of 4-vinylcyclohexene and its main oxirane metabolite on mouse hepatic microsomal enzymes and glutathione levels

When 4-vinylcyclohexene (VCHE) and 4-vinylcyclohexene monoxide (VCM) were administered to mice at 500 mg/kg, cytochrome P-450, cytochrome b 5, NADPH-cytochrome c reductase and aminopyrine- N-demethylase and epoxide hydrolase were induced. Doses of 500 mg/kg of VCHE, VCM and 4-vinylcyclohexene diepoxide depleted rapidly hepatic reduced glutathione levels suggesting that glutathione is probably involved in the metabolism of VCHE.