Effects of organosulfur compounds from garlic oil on the antioxidation system in rat liver and red blood cells.

The modulation of garlic oil (GO) and three allyl compounds, diallyl sulfide (DAS), diallyl disulfide (DADS) and diallyl trisulfide (DATS), on the antioxidation system in rat livers and red blood cells was examined. Rats were orally administered GO (200 mg/kg body weight), DAS (20, 80 mg/kg body weight), DADS (80 mg/kg body weight) or DATS (70 mg/kg body weight) three times a week for 6 weeks. Control rats received corn oil (2 ml/kg body weight) alone. GO, DADS and DATS treatment significantly increased the glutathione (GSH) content (48-84%) in red blood cells (P < 0.05). DATS displayed a greater enhancement than GO and DADS (P < 0.05). Hemolysis induced by tert-butyl hydroperoxide was not suppressed by GO or allyl compound treatment although higher GSH content was evident. Hepatic GSH was not influenced by garlic components. In rat livers, DADS and DATS significantly increased the activity of GSH reductase (46 and 54%, respectively) and of GSH S-transferase (GST) (63 and 103%, respectively), but decreased the GSH peroxidase activity (27 and 28%, respectively). In contrast, GSH reductase and GST activities in the DAS group, either 20 or 80 mg/kg body weight, were similar to the control group. A decrease of GSH peroxidase activity was observed in rats dosed with 80 mg/kg body weight (P < 0.05). An increase in GST activity and a decrease in GSH peroxidase activities were also noted in GO-treated rats (P < 0.05). In red blood cells, three GSH-related antioxidant enzyme activities were not affected by garlic oil and its organosulfur components. Immunoblot assay showed that, accompanying the increase in hepatic GST activity, GO, DADS, DAS (80 mg/kg body weight) and DATS increased the expression of GST Ya, Yb1 and Yc proteins. Results indicate that GO and three allyl compounds play a differential role in modulation of the GSH-related antioxidant system in rat livers and red blood cells.     

Papaverine, an opium alkaloid influences hepatic and pulmonary glutathione S-transferase activity and glutathione content in rats.

The present study evaluates the effect of oral administration of papaverine at differential dosing regimens (100 mg/kg bw and 200 mg/kg bw) on the hepatic and pulmonary glutathione S-transferase (GST) activity and glutathione content (GSH) in male Wistar rats. Papaverine treatment caused a pronounced increase in GST activity and GSH content at the higher dosing level in the rat liver and lung. We conclude that papaverine, can possibly act as a chemopreventive agent against chemical carcinogenesis.     

Difference in the effects of phenobarbital and 3-methylcholanthrene treatment on subunit composition of hepatic glutathione S-transferase in male and female rats

Male rats more than seven weeks old showed significantly higher activity of hepatic cytosolic glutathione S-transferase (GST) than females. This sex-related difference in GST activities might be explained by the difference in subunit composition of the enzymes between males and females. The relative proportion of subunit composition of GST between adult male and female rats was as follows: Ya, female greater than male; Yb(Yb'), male much greater than female; Yc, female greater than male. Since phenobarbital (60 mg/kg, i.p. for seven days) induced the Yb subunit as well as Ya subunit, the enzyme activity was more increased in males than in females and the sex difference became more marked. 3-Methylcholanthrene (20 mg/kg, i.p. three times) caused an increase of Ya subunit alone, and then the increased extent was greater in females than in males, and resulted in the disappearance of sex difference.     

Modification by phenobarbital of decreased glutathione content and glutathione S-transferase activity in livers of lead-treated mice.

Lead acetate (100 mg/kg) administered i.p. to male mice decreased hepatic glutathione (GSH) content and also glutathione S-transferase (GST) activity. However, the liver GSH content of mice treated with both lead and phenobarbital (80 mg/kg, i.p.) remained unchanged, whereas their GST activities were higher than the controls. Phenobarbital antagonized the Pb-induced decrease in liver adenosine triphosphate content. Additionally, phenobarbital shortened the half-life of hepatic GSH determined using buthionine sulfoximine, an inhibitor of GSH synthesis. Acceleration of hepatic GSH turnover by phenobarbital possibly diminishes the Pb-induced impairment of GSH-conjugation of xenobiotics.     

Effects of rosmarinic acid on acetaminophen-induced hepatotoxicity in male Wistar rats

Context: Drug-induced liver injury is a significant worldwide clinical problem. Rosmarinic acid (RA), a natural phenol, has antioxidant effects.

Objective: The effects of RA against acetaminophen (N-acetyl-p-amino-phenol (APAP))-induced oxidative damage and hepatotoxicity in rats were investigated.

Materials and methods: Male Wistar rats were pretreated with RA (10, 50 and 100?mg/kg, i.g.) for one week. On day 7, rats received APAP (500?mg/kg, i.p.). Then aspartate aminotransferase (AST), alanine aminotransferase (ALT), albumin, total protein, malondialdehyde (MDA), glutathione (GSH), total antioxidant capacity (TAC), glutathione S-transferase (GST), cytochrome CYP450 and histopathological changes were determined.

Results: APAP-induced oxidative stress in liver by a significant increase in the level of MDA (7.6?±?0.21?nmol/mg) as well as a decrease in the contents of TAC (1.75?±?0.14?μmol/g), GSH (1.9?±?0.22?μmol/g) and GST) 3.2?±?0.28?U/mg). RA treatment decreased MDA (4.32?±?0.35?nmol/mg) but increased the contents of TAC (3.51?±?0.34?μmol/g), GSH (3.42?±?0.16?μmol/g) and GST (5.71?±?0.71?μmol/g) in APAP group. RA 100?mg/kg decreased ALT (91.5?±?1.5?U/L), AST (169?±?8.8?U/L) and CYP450 (3?±?0.2?nmol/min/mg) in APAP group. Histologically RA attenuated hepatic damage by decreasing necrosis, inflammation, and haemorrhage in liver sections of APAP group.

Discussion and conclusions: This is the first report that oral administration of RA dose-dependently elicited significant hepatoprotective effects in rats through inhibition of hepatic CYP2E1 activity and lipid peroxidation. RA-protected hepatic GSH and GST reserves and total tissue antioxidant capacity.     

阿魏酸钠对乙醇所致小鼠肝脏抗氧化功能改变的拮抗作用

研究了不同剂量乙醇对小鼠抗氧化和解毒功能的影响以及阿魏酸钠的拮抗作用。结果表明,大剂量乙醇(11.4g·kg^-1ig)引起肝脏GSH-Px活性升高的同时,肝脏GSH-Re,SOD和GST活性降低,GSH耗竭,而血清GST升高;阿魏酸钠(100mg·kg^-1ig,qd×10)预处理则明显拮抗大剂量乙醇所致的上述改变。表明阿魏酸钠对急性乙醇所致肝损害具有良好保护作用,其机理可能与提高GSH氧化还原酶功能、增加SOD活性和增强GSH结合反应有关。研究结果还提示,血清GST水平是反映乙醇性肝损害的灵敏指标。     

Effects of buthionine sulfoximine and cysteine on the hepatotoxicity of butylated hydroxytoluene in rats

Pretreatment with buthionine sulfoximine (BSO; 900 mg/kg) induced the elevation of serum GOT and GPT activities in a non-toxic dose of butylated hydroxytoluene (BHT; 250-500 mg/kg) in rats. The elevation of serum enzyme activities was accompanied by a remarked depletion of the hepatic glutathione (GSH) concentration. In contrast, pretreatment with cysteine (100-200 mg/kg) inhibited the elevation of serum enzyme activities at a toxic dose of BHT (1000 mg/kg). The effects of BSO and cysteine on BHT-induced hepatotoxicity in rats are discussed.     

Resveratrol modulates pyrogallol-induced changes in hepatic toxicity markers, xenobiotic metabolizing enzymes and oxidative stress

Previously, we reported that pyrogallol, an anti-psoriatic agent, causes hepatotoxicity in experimental animals and silymarin, an herbal antioxidant, reduces pyrogallol-induced changes [Upadhyay, G., Kumar, A., Singh, M.P., 2007. Effect of silymarin on pyrogallol- and rifampicin-induced hepatotoxicity in mouse. Eur. J. Pharmacol. 565, 190-201.]. The present study was undertaken to assess the effect of resveratrol against pyrogallol-induced changes in hepatic damage markers, xenobiotic metabolizing enzymes and oxidative stress. Swiss albino mice were treated intraperitoneally, daily with pyrogallol (40 mg/kg), for one to four weeks, along with respective controls. In some set of experiments, animals were pre-treated with resveratrol (10 mg/kg), 2 h prior to pyrogallol treatment, along with respective controls. Alanine aminotransaminase, aspartate aminotransaminase and bilirubin were measured in blood plasma and mRNA expression of cytochrome P-450 (CYP) 1A1, CYP1A2, CYP2E1, glutathione-S-transferase (GST)-ya and GST-yc, catalytic activity of CYP1A1, CYP1A2, CYP2E1, GST, glutathione reductase and glutathione peroxidase, lipid peroxidation and reduced glutathione (GSH) level were measured in liver. Resveratrol reduced pyrogallol-mediated increase in alanine aminotransaminase, aspartate aminotransaminase, bilirubin, lipid peroxidation and mRNA expression and catalytic activity of CYP2E1 and CYP1A2. Pyrogallol-mediated decrease in GST-ya and GST-yc expressions, GST, glutathione peroxidase and glutathione reductase activities and GSH content was significantly attenuated in resveratrol co-treated animals. CYP1A1 expression and catalytic activity were not altered significantly in any treated groups. The results demonstrate that resveratrol modulates pyrogallol-induced changes in hepatic toxicity markers, xenobiotic metabolizing enzymes and oxidative stress.     

Hepatotoxicity of ketoconazole in Sprague-Dawley rats: glutathione depletion,flavin-containing monooxygenases-mediated bioactivation and hepatic covalent binding

1. This study has examined ketoconazole (KT)-induced hepatotoxicity in vivo and in vitro, using male Sprague-Dawley rats with [3 H]KT (1.5 µCi?mg ? 1) at 40 and 90?mg KT kg ? 1 doses. Blood and liver samples were collected from 0 to 24?h for alanine aminotransaminase (ALT), glutathione (GSH) and covalent binding analyses. 2. Covalent binding occurred as early as 0.5?h, peaked at 2?h (0.026 ± 0.01 nmol KT?mg ? 1 protein) and 8?h (0.088 ± 0.04 nmol KT?mg ? 1 protein) for 40 and 90?mg KT kg ? 1 doses, respectively. ALT levels increased at 0.5?h for the 40 and 90?mg KT kg ? 1 doses (44.3 and 56.4 U ml ? 1, respectively) relative to control, 22.7 U ml ? 1. At 24?h, the 90?mg KT kg ? 1 dose reduced hepatic GSH levels from 9.92 ± 1.1 to 4.76 ± 0.3 nmol GSH?mg ? 1 protein. 3. The role of the flavin-containing monooxygenases (FMO) utilized Sprague-Dawley microsomes with 1, 10 and 100 µM [3 H]KT. Maximum covalent binding occurring at 100 µM KT. Heat inactivation of microsomal FMO significantly decreased covalent binding by 75%, whereas 1 mM GSH significantly reduced covalent binding by 65%. 4. Thus, KT-induced hepatotoxicity is dose- and time-dependent and appears to be FMO mediated, in part, to metabolites that may react with protein and, possibly, GSH.     

双环醇对大鼠黄曲霉毒素B1代谢和肝毒性的影响

目的:研究抗肝炎新药双环醇对大鼠黄曲霉毒素B_1(AFB_1)代谢和肝毒性的影响.方法:大鼠灌胃双环醇300 mg·kg~(-1)·d~(-1),连服三日后腹腔注射黄曲霉毒素B_1 1.5 mg·kg~(-1).给黄曲霉毒素B_1 16小时后观察双环醇对黄曲霉毒素B_1引起肝损伤的防护作用以及对体外代谢的影响.结果:双环醇(300 mg·kg~(-1)·d~(-1),连服三日)可明显降低黄曲霉毒素B_1引起的大鼠血清转氨酶和肝脏MDA的升高,增加低毒代谢产物AFQ_1的生成.双环醇还可增加大鼠肝脏细胞色素P450总量和胞浆谷胱甘肽含量,诱导P450 CYP2B1介导的7-戊氧基香豆素脱烃酶和谷胱甘肽疏基转移酶的活性.此外,双环醇对P450 CYP3A介导的红霉素脱甲基酶和 P450 CYP1A介导的7-乙氧基香豆素脱烃酶也有诱导作用.结论:双环醇可通过增加大鼠肝脏对AFB_1代谢的解毒功能起到肝保护作用.     

Effect of pregnenolone-16 alpha-carbonitrile and dexamethasone on acetaminophen-induced hepatotoxicity in mice.

Recently, we demonstrated that a microsomal enzyme inducer with a steroidal structure, pregnenolone-16 alpha-carbonitrile (PCN), markedly decreased the hepatotoxicity of acetaminophen (AA) in hamsters. Therefore, it was of interest to determine if PCN, as well as another steroid microsomal enzyme inducer, dexamethasone (DEX), would decrease the toxicity of AA in mice, another species sensitive to AA hepatotoxicity. Mice were pretreated with PCN or DEX (100 and 75 mg/kg, ip, for 4 days, respectively) and were given AA (300-500 mg/kg, ip). Twenty-four hours after AA administration, liver injury was assessed by measuring serum activities of sorbitol dehydrogenase and alanine aminotransferase and by histopathological examination. Neither PCN nor DEX protected markedly against AA hepatotoxicity in mice; PCN tended to decrease AA-induced hepatotoxicity, whereas DEX was found to enhance AA-induced hepatotoxicity and it produced some hepatotoxicity itself. DEX decreased the glutathione concentration (36%) in liver and increased the biliary excretion of AA-GSH, which reflects the activation of AA, whereas PCN produced neither effect. Thus, whereas PCN has been shown to markedly decrease the hepatotoxicity of AA in hamsters, apparently by decreasing the isoform of P450 responsible for activating AA to N-acetyl-p-benzoquinoneimine, this does not occur in mice after induction with either PCN or DEX. In contrast, DEX enhances AA hepatotoxicity apparently by decreasing liver GSH levels and increasing the activation of AA to a cytotoxic metabolite.     

Changes in hepatic phase I and phase II biotransformation enzyme expression and glutathione levels following atrazine exposure in female rats

1. To determine the effects of repeated atrazine (ATR) treatment on hepatic phase I and II enzymes, adult female rats were treated with vehicle or 100?mg/kg of ATR for 1, 2, 3 or 4 days. Glutathione-s-transferases (GST) mRNA expression, protein levels (mu, pi, alpha, omega), and activity (cytosolic and microsomal), along with bioavailable glutathione (GSH) were assayed.

2. GST expression, concentrations and activity were increased, along with GSH levels, in animals treated with ATR for 3 and 4 days.

3. A subsequent study was performed with animals treated with vehicle, 6.5, 50 or 100?mg/kg/day for 4, 8 or 14 days. Expression of hepatic phase I CYP 450 enzymes was evaluated in conjugation with GST expression, protein and activity. Nineteen of the 45 CYP enzymes assayed displayed increased mRNA levels after eight?days of treatment in animals treated with 50 or 100?mg/kg/day. After 14 days of treatment, all CYP expression levels returned to control levels except for CYP2B2, CYP2B3, CYP2C7, CYP2C23, CYP2E1, CYP3A9, CYP4A3 and CYP27A1, which remained elevated.

4. Results indicate that there may be a habituation or adaptation of liver phase I and phase II expression following repeated ATR treatment.     

Induction of glutathione synthesis explains pharmacodynamics of high-dose busulfan in mice and highlights putative mechanisms of drug interaction.

Busulfan is an example of a drug eliminated through glutathione S-transferase (GST)-catalyzed conjugation with reduced glutathione (GSH). We studied the pharmacokinetics and toxicity of busulfan in C57BL6 mice in correlation with liver GST activity and GSH synthesis by accurate determination of precursors, namely, gamma-glutamyl-cysteine and cysteine. A significantly lower incidence of acute toxicity was observed in mice receiving busulfan 16.5 mg/kg twice a day compared with animals receiving 33 mg/kg once a day. In both cases, a total dose of 132 mg/kg was administered over 4 days. The difference in toxicity was explained by pharmacokinetics since a strong induction of clearance was observed only in animals treated twice daily. Induction of metabolism was correlated with an increase in liver cysteine content and enhanced glutathione synthesis rate, whereas GST activity was unchanged. To our knowledge, this is the first time that in vivo flux of GSH synthesis has been shown to be closely related to a drug plasma clearance and toxicity. These results allow hypothesizing that GSH liver synthesis may directly influence busulfan clearance in humans with possible implications in the occurrence of hepatic veno-occlusive disease.     

Hepatotoxicity of N-methylformamide in mice--I. Relationship to glutathione status

In order to investigate the link between hepatotoxicity caused by N-methylformamide (NMF) and its ability to deplete hepatic glutathione experiments were conducted in three strains of mouse which differ in their susceptibility towards NMF-induced liver damage. NMF toxicity was measured by changes in plasma levels of sorbitol dehydrogenase and alanine and aspartate transaminases. In BALB/c mice, the most susceptible strain, a hepatotoxic dose of NMF (200 mg/kg) caused a depletion of hepatic glutathione to 21% of control levels 2 hr after drug administration. In CBA/CA and BDF1 mice the same dose of NMF depleted glutathione to 53% of control levels and did not cause hepatotoxicity. In BALB/c mice depletion of hepatic glutathione by pretreatment with buthionine sulfoximine decreased the hepatotoxic dose threshold of NMF from 150 mg/kg to 100 mg/kg. Conversely, pretreatment of mice with cysteine or N-acetylcysteine protected against both glutathione depletion and NMF-induced hepatotoxicity. The results are in accordance with the suggestion that the hepatotoxicity of NMF is associated with its metabolism to an intermediate which reacts with glutathione.     

The effects of bucillamine on glutathione and glutathione-related enzymes in the mouse

The effect of bucillamine (BA) on glutathione (GSH) and GSH-related enzymes was investigated in C57 mouse. Administration of high doses of BA (150-400 mg/kg) produced a dose-dependent depletion (20-44%) of hepatic GSH, which was similar in magnitude to that produced by equimolar doses of other sulphydryl drugs studied previously. GSH depletion after acute BA administration correlated well with the elevation of serum glutamic-pyruvic transaminase (SGPT) (6-9-fold increase above control). The increase in SGPT after chronic administration (7 days), although significantly higher than the controls, was however much less than after acute administration. The hepatic GSH concentrations of mice given 7 days of BA were similar to the controls, again correlating well with SGPT activity. Administration of BA (150-400 mg/kg) caused also a significant dose-dependent increase in the oxidized glutathione (GSSG) in blood by 2-7-fold, as well as a dose-dependent increase in blood glutathione S-transferase (GST) activity (2-13-fold). In an in vitro experiment, hepatic GST activity was activated by various concentrations of BA (1 microM-1mM). There was little or no effect on GSSG reductase and on glutathione peroxidase (GSH-Px) after acute administration of BA. Chronic administration of BA had no effect on hepatic GSSG reductase and GSH-Px, but GSSG reductase activity in blood was increased significantly by 4-fold. It is possible that BA may affect the redox status through auto-oxidation and oxidation with endogenous thiols such as glutathione, affecting GSH concentrations and the GSH/GSSG ratio in tissues and, thus, having both metabolic and toxicological consequences. Whether or not the induction of GST activity in vivo in blood and in vitro in liver enzyme preparations shared the same underlying mechanism(s) requires further investigation.     

Identification of glutathione conjugates of 1-bromopentane and its hepatotoxicity in female BALB/c mice

Halogenated organic compounds, such as 1-bromopentane (1-BPT), are used as cleaning agents, synthesis agents, or extraction solvents in the workplace. In the present study, glutathione (GSH) conjugation and hepatotoxicity induced by 1-BPT were investigated in female BALB/c mice. S-Bromopentyl GSH, S-bromopentyl cysteine, and mono-hydroxypentyl mercapturic acid were identified in liver by liquid chromatography-electrospray ionization tandem mass spectrometry. Oral treatment of mice with 1-BPT at 1500 mg/kg produced maximum GSH conjugates at 6 h after treatment. For hepatotoxicity tests, the animals were treated orally with 1-BPT at 375, 750, or 1500 mg/kg in corn oil once for a dose response study or at 1500 mg/kg for 6, 12, 24, or 48 h for a time course study. 1-BPT dose-dependently increased serum activity of ALT and AST and decreased hepatic GSH levels, peaking at 6 and 12 h after treatment. 1-BPT (750 and 1500 mg/kg) also significantly increased the hepatic content of malondialdehyde. Thus, 1-BPT could cause hepatotoxicity and depletion of GSH content by forming GSH conjugates, presenting a toxicity mechanism and potential biomarkers for low molecular weight haloalkanes.     

Carbon tetrachloride-induced changes in the activity of phase II drug-metabolizing enzyme in the liver of male rats: role of antioxidants

Glutathione S-transferases and glutathione play an important role in the detoxification of most toxic agents. In the present study, the protective effects of some antioxidants (L-ascorbic acid (AA), vitamin E (VE) or garlic) on carbon tetrachloride-induced changes in the activity of alanine amino transferase (ALT), aspartate amino transferase (AST), glutathione S-transferase (GST), and the level of glutathione (GSH) and thiobarbituric acid reactive substances (TBARS) were studied. The activities of ALT, and AST were assayed in plasma, whereas the activity of GST and the levels of GSH and TBARS were determined in the livers of rats. The current study included two experiments. In the first experiment, animals received single oral dose of CCl4 (400 mg/kg body weight) after administration of AA (100 mg/kg b.w.), VE (100 mg/kg b.w.) or garlic (800 mg/kg b.w.) as single oral doses. In the second experiment, rats received repeated oral doses of antioxidants for 12 consecutive days followed by a single oral dose of CCl4 on the 13th day and killed after that by 24 h. Treatment of male rats with CCl4 significantly increased the activity of ALT and AST in plasma, and the levels of both GSH and TBARS in the liver. On the other hand, CCl4 inhibited the activity of GST after single dose treatment. Single-dose treatments of rats with AA, VE or garlic prior to the administration of CCl4 could not restore the alterations in the activity of ALT and AST caused by CCl4 to the normal control level. However, repeated dose treatments with these agents restored such alterations to the normal level. We observed that VE is more effective than AA and garlic in restoring the inhibition of GST activity caused by CCl4 to the normal level after single dose treatments. On the other hand, AA and VE are more effective than garlic in restoring the induced TBARS level caused by CCl4 to the normal control level after repeated dose treatments. It has been observed that the tested antioxidants were able to antagonize the toxic effects of CCl4, and such counteracting effects were more pronounced when they were administered as repeated doses prior to administration of CCl4.     

Vitamin C protects against in vitro cytotoxicity of cypermethrin in rat hepatocytes.

The objective of this study was to investigate the effect of ascorbic acid (AA) on the in vitro cytotoxicity of cypermethrin (CM), and on glutathione (GSH) metabolism in rat hepatocytes. In vitro cell viability, lactate dehydrogenase (LDH), alanine aminotransferase (ALT) and aspartate aminotransferase (AST) leakage were measured, as indicators of hepatic damage, at 1, 15 and 30 min of exposure to CM. Glutathione and the activities of glutathione-S-transferase (GST) and gamma glutamyl transpeptidase (gamma-GT) were also measured. CM hepatotoxicity increased in a time and dose-dependent manner. In the presence of 30 microM CM, ALT and AST also increased 49 and 130% (P < 0.05), respectively, indicating metabolic hepatocyte damage. AA (1 mM) was capable to preserve 100% of cell integrity and modulated ALT and AST. Furthermore, CM induced a 27% reduction in the endogenous antioxidant GSH, and increased 203% GST and 283% gamma-GT (P < 0.05), indicating an oxidative insult. The presence of AA showed chemopreventive capacity against CM, recovering 60% of GSH and a 54% decrease in gamma-GT activity. These results suggest that AA in a 1:33 (CM:AA) ratio can modulate up to 90% of the damage caused to the cells by CM. It also demonstrates that AA can act as a primary antioxidant and hepatoprotector in rat hepatocytes.     

Sequential changes in hepatic and renal glutathione and development of renal karyomegaly in 1-cyano-3,4-epithiobutane toxicity in rats

The effect of 1-cyano-3,4-epithiobutane (CEB) on glutathione (GSH) metabolism was investigated in rat liver, kidney and pancreas. Male Fischer 344 rats were gavaged with a single dose (125 mg/kg body weight or 50 mg/kg body weight) of CEB. Tissue samples were taken for histological examination, determination of GSH and oxidized glutathione (GSSG) concentrations and gamma-glutamyl transpeptidase (GGT) and glutathione S-transferase (GST) activities. Urine samples were analysed for non-protein thiol (NP-RSH) content. The high dose of CEB induced hepatic GSH depletion followed by increased GSH. The low dose of CEB induced elevated hepatic GSH by 12 hr without depletion. Renal GSH was increased with both doses without an observed depletion phase. Renal tubule epithelial cell death was observed only with the high dose of CEB, but both doses caused renal proximal tubule karyomegaly. Pancreatic GSH content was unaffected. No alterations of GSSG were observed. GST activity was unaffected in any tissue. Renal GGT activity was decreased at 12 hr with both doses and at 24 and 48 hr with the high dose. Urinary NP-RSH excretion was increased with both doses. Depletion of hepatic GSH concurrent with increased urinary NP-RSH excretion suggests that conjugation with GSH is a significant pathway in CEB metabolism.