Enhancement of Pancreatic and Hepatic Glutathione Levels in Rats during Cyanohydroxybutene Intoxication

Enhancement of Pancreatic and Hepatic Glutathione Levels inRats during Cyanohydroxybutene Intoxication. WALLIG, M. A.,AND JEFFERY, E. H. (1990) Fundam. Appl. Toxicol. 14, 144–159.l-Cyano-2-hydroxy-3-butene (CHB), a cruciferous plant product,is hepatotoxic, pancreatotoxic, and elevates glutathione (GSH)in liver and pancreas. Whether GSH elevation is preceded bya depletion related to toxic insult, or whether toxicity andGSH elevation are unrelated, is not known. To evaluate the temporalrelationship between toxicity and GSH levels, male Fisher 344rats (6/group) were given CHB (200 mg/kg po) and killed up to96 hr after dosing. At death, histological and ultrastructuralevaluations and GSH/GSSG determinations were performed on liverand pancreas. In pancreas, dilatation of the cisternae of therough endoplasmic reticulum (RER) was evident from 2 hr, becomingprogressively more severe 4 and 6 hr after CHB. Frank apoptosisand loss of zymogen granules was evident by 6 hr, becoming widespreadby 12 hr. Recovery had commenced by 72 hr, and 50% of treatedrats had normal pancreata by 96 hr. No hepatic lesions wereobserved at this dose. Pancreatic GSH was depressed below 20%at 2 and 4 hr, rose to a maximum of 540% by 12 hr, and remainedelevated in treated rats throughout the study (275% at 96 hr).Hepatic GSH only fell to 50%, rose to 150-180%, and returnedto normal by 96 hr. While this pattern of depletion and reboundfollowing exposure to hepatotoxins is common, the exaggeratedand persistent elevation of pancreatic GSH is unprecedented.     

The toxicology of the schistosomicidal agent oxamniquine

Oxamniquine displayed low acute toxicity in mice, hamsters, and rabbits. In rats, however, oxamniquine was much more toxic, the female being 8–10 times more sensitive than the male; single doses elicited an idiosyncratic sex-linked hepatic necrosis and bile duct proliferation. Dogs given repeated oral doses of 20 or 30 mg/kg/day for 5 successive days every 4 weeks for 11 months showed neurological disturbances of short duration, which tended gradually to increase in severity from one dosage period to the next; no histopathological correlate could be found. In chronic studies in mice (18 months) and hamsters (19 months) with intermittent dosage regimens relevant to likely usage in man, no evidence of carcinogenicity potential was observed at dose levels up to 150 mg/kg. Oxamniquine displayed no maternal toxicity or teratogenicity in mice and rabbits, and only slight embryotoxicity after high oral doses.     

Dose-response hapatotoxicity of the peroxisome proliferator, perfluorodecanoic acid and the relationship to phospholipid metabolism in rats.

Perfluorodecanoic acid (PFDA) is a potent peroxisome proliferator that causes hepatotoxicity but lacks tumor-promoting activity in rats. We previously showed that a single dose of PFDA at 50 mg/kg (approximately LD50) causes an elevation in liver phosphocholine (PCho) and other effects related to phospholipid metabolism. In this study, we examined metabolic effects in the dose range 2-50 mg/kg in rats. At doses < or =20 mg/kg, PFDA is significantly less hepatotoxic than the LD50 as manifested by electron microscopy and measurements of daily food consumption and body weight. At 50 mg/kg rat serum tumor necrosis factor (TNF)-alpha concentration was increased 8-fold, while at 15 mg/kg there was no apparent increase in this cytokine. This lower dose, however, induces metabolic effects similar to those seen at the LD50. Liver fatty acyl-CoA oxidase activity showed a dose-dependent increase from 5-25 mg/kg PFDA. Treatments at 15 and 50 mg/kg caused a significant increase in liver phosphatidylcholine (28 and 66%) and phosphatidylethanolamine (31 and 74%). Both doses caused a significant increase in liver PCho but did not affect liver ATP levels, as manifested in 31P nuclear magnetic resonance (NMR) spectra from rat livers in vivo. These data suggest that the increase in liver [PCho] observed following PFDA exposure in rats represents a specific metabolic response, rather than a broad-range hepatotoxic effect.     

Comparison of the depletion of glutathione in mouse liver and lung following administration of styrene and its metabolites styrene oxide and 4-vinylphenol

Styrene is hepatotoxic and pneumotoxic in mice. Its major metabolite styrene oxide and its minor, but potent, metabolite 4-vinylphenol cause similar toxicities. Styrene and styrene oxide cause decreases in reduced glutathione levels in tissues. The current studies examined styrene and styrene oxide in a time and dose-dependent manner and 4-vinylphenol in a time dependent fashion. Styrene (600 mg/kg, 5.8 mmol/kg ip) caused decreased GSH levels in both liver and lung within one hour. A maximum was seen at three hours with return to control levels by 12 h. Lower doses also caused changes in a dose-dependent fashion. For styrene oxide, similar findings were observed with a dose of 300 mg/kg (2.5 mmol/kg). GSH levels in liver, but not lung, returned to control by 6 h. Again a dose response was found for both tissues. While 4-vinylphenol (100 mg/kg, 0.83 mmol/kg) was administered at a dose known to be more hepatotoxic and more pneumotoxic than styrene or styrene oxide and it caused decreased GSH levels, the degree of depletion was less compared to styrene and styrene oxide. In general the lung was more affected by these agents than was liver. The decreases in GSH suggest the possibility that the toxicity of styrene in lung and liver may be related to a profound but reversible oxidative stress in these tissues.     

Biological responses of the rat to polychlorinated biphenyls

A commercial polychlorinated biphenyl mixture (PCBs), Aroclor 1242, was administered to rats po by intubation in order to determine toxic manifestations of acute and subacute ingestion. In addition, the effect of PCBs on hepatic microsomal enzyme systems in rats was evaluated. The oral, 14-day LD50 was determined to be approximately 4.25 g/kg. Major toxic signs observed upon administration of high doses of PCBs included diarrhea, chromodacryorrhea, loss of body weight, unusual stance and gait, lack of response to pain stimuli, and terminal ataxia. Progressive dehydration and CNS depression appeared to be contributing factors in each fatality. Histopathologic alterations were evident only in the liver and kidneys, manifest as foci of sudanophilic vacuolation. Rats maintained on an oral dosage regimen of 100 mg/kg every other day for 3 weeks exhibited similar histopathologic changes, but no overt signs of toxicity. Serum GOT activities were elevated over controls in both the acute and subacute groups. A single ip injection (100 mg/kg) increased liver weight, total hepatic microsomal enzyme activity (measured as hydroxylation of acetanilide and N-demethylation of aminopyrine), and hepatic cytochrome P₄₅₀ and b₅ levels. Hepatic microsomal enzyme activity remained elevated 10 days after a single dose of PCBs, suggesting that PCBs may play an important role in altering biologic responses of mammals subjected to environmental chemical stress.     

Citrinin mycotoxicosis in the rabbit

In three trials, single or multiple doses of citrinin dissolved in 0.5 N-NaOH and adjusted to neutral pH with HCl were given to rabbits by either the oral or intraperitoneal route. The 72-hr LD50 was 50 mg/kg body weight by intraperitoneal administration and 134 mg/kg by the oral route. The primary clinical sign in rabbits receiving a single oral dose of 125-150 mg citrinin/kg was fluid diarrhoea commencing 8 hr after dosing. Pathological alterations were generally confined to the kidney and consisted of degeneration and necrosis of proximal convoluted tubules and straight segments. In rabbits given a single oral dose of citrinin (130 mg/kg) the earliest histopathological change, seen 8 hr after dosing, was cytoplasmic vacuolation of tubular epithelial cells. Rabbits given a single oral dose of 120 mg citrinin/kg had regeneration of renal tubular epithelium accompanied by slight tubular cell necrosis when examined 7 days after dosing. Rabbits given multiple sublethal doses of citrinin (33.5 or 77 mg/kg daily for 7 days) had renal alterations of mild tubular degeneration and necrosis, and tubular regeneration.     

Effect of Amiodarone and Desethylamiodarone on the Pharmacokinetics of Antipyrine in the Rat

The effect of amiodarone on hepatic drug metabolism in vivo was examined in the rat using antipyrine as a model substrate. Pretreatment with oral amiodarone hydrochloride, 100 mg/kg/day, for 5 days resulted in a 19% reduction in antipyrine clearance and a 22% increase in half-life. The administration of single oral doses of amiodarone hydrochloride, 100 mg/kg, 1 or 5 hr prior to antipyrine administration had no significant effect on antipyrine pharmacokinetics. The administration of a single intravenous dose of amiodarone hydrochloride, 50 mg/kg, reduced antipyrine clearance by 32% and increased the half-life by 46%. The desethyl metabolite of amiodarone was also found to reduce antipyrine clearance (21%) after a single oral dose of 100 mg/kg.     

Manipulation of mouse organ glutathione contents. II: Time and dose-dependent induction of the glutathione conjugation system by phenolic antioxidants

After 14 days of oral butylated hydroxyanisole (BHA) administration (1000 mg/kg/day) the tissue glutathione levels of male NMRI mice were increased by 74-141% in liver, lung, duodenum and intestine and after similar butylated hydroxytoluene (BHT) treatment by 18-85% in the liver, lung, spleen and the gastrointestinal tract. Doses of 100 mg/kg/day significantly elevated the glutathione content in the lung (BHA, BHT), duodenum (BHA) and intestine (BHA), while 10 mg/kg/day affected only lung glutathione content (BHA). BHA treatment (1000 mg/kg/day) induced GST activities significantly (138-1335%) in all organs investigated except the spleen, i.e. liver, lung, kidney and the entire gastrointestinal tract, while a similar dose of BHT increased GST activities in the liver, duodenum, intestine and colon by 26-339%. Daily doses of 100 mg/kg/day significantly induced GST activities only in the liver (BHA, BHT), lung (BHA) and kidney (BHA). Lower doses of BHA or BHT did not significantly affect GST activities in the organs investigated (except 10 mg BHA/kg/day in the lung). Comparison of the time course of induction of the glutathione conjugation system in various organs after different doses of antioxidants indicated no change between 5 and 14 days of treatment with all doses used (1-1000 mg/kg). Only the lung glutathione level showed a tendency to increase with low dose BHA by extending the time of treatment. The time course of the liver glutathione content between single doses of 100 mg/kg BHA or BHT revealed an initial decline followed by an increase above control values 2 days (BHA) or 5 days (BHT) after the first application. The glutathione levels of the lung and the duodenum increased without a preceding decline. Only the second dose of BHT caused a temporary decrease to control values of the elevated glutathione level in the duodenum. All animals (at any dose of BHA or BHT) showed control values of serum transaminase activities. These results suggest: The induction threshold of the glutathione conjugation system in various mouse organs is greater than or equal to 100 mg/kg for BHA and BHT. Chronic administration of these compounds did not change these results (except the lung glutathione level after low dose BHA). Elevated hepatic glutathione levels might be the result of an activated synthesis caused by a preceding loss of glutathione. Chronic BHA or BHT treatment did not cause hepatotoxic effects, as evaluated by serum transaminases, in male mice.     

Toxicity Studies with Fluindarol, 2-[p-(trifluoromethyl)phenyl]1, 3-indandione,an Agent with Anticoagulant Properties (BS 7616 D)

The phenylindandione derivative fluindarol was subjected to a toxicological investigation in view of its possible use as an anticoagulant in man. The acute oral LD50 in rats and rabbits was 198 and 123 mg/kg, respectively. The acute intraperitoneal LD50 in the rat was 125 mg/kg. Dogs survived single oral doses of up to 2810 mg/kg; if the drug was given for four consecutive days, an oral LD50 of 118 mg/kg was obtained. In a four-week experiment in the rat, doses ranging from 108 to 7 mg/kg caused mortality which occurred sooner and more frequently in the females than the males; the organs showed haemorrhages and at the higher dose levels the liver showed parenchymal necrosis. Similar results were obtained with chlorindione, which tended to be somewhat less toxic. It was confirmed that a distinction should be made between the “toxicity” of an anticoagulant which is due to its pharmacological properties and true organ toxicity. Fluindarol was considered too toxic for clinical use.     

Effect of ketamine pretreatment on cocaine-mediated hepatotoxicity in rats

Cocaine (COC) produces hepatotoxicity by a mechanism, which remains undefined, but has been linked to its oxidative metabolism. Ketamine (KET) is also a potentially hepatotoxic agent. The abuse of KET with COC is currently popular among young abusers therefore; this study was conducted to investigate the possible potentiation of COC-mediated hepatotoxicity (CMH) by KET. Male Sprague Dawley (SD) rats were administered oral KET hydrochloride for three consecutive days at a dose of 100 mg/kg with and without a single dose of COC (5 mg/kg, i.v.) administered 18 h after the last KET dose. Serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) were measured as markers of liver injury. Liver reduced glutathione (GSH) levels were determined as well as the activities of glutathione peroxidase (GPx) and catalase (CAT). In addition, the activity of liver glutathione reductase (GRx) was measured. The results demonstrate that KET pretreatment potentiated the hepatotoxicity of COC. Serum ALT and AST were significantly elevated with the combined KET and COC treatment versus all other treatments. While COC alone resulted in focal inflammatory cell infiltration, COC administration after KET pretreatment produced sub-massive hepatic necrosis. Hepatic GSH content was significantly reduced in KET-pretreated COC group compared to the other treatment groups, rendering the liver more susceptible to oxidative stress. Moreover, there was a significant decrease in the activities of hepatic GPx and CAT, particularly with the KET-pretreated COC group. In addition, norcocaine (NC) was only detected in the plasma of rats received COC after KET pretreatment. In conclusion, this study demonstrates that KET pretreatment potentiates the hepatotoxicity of COC as revealed by an array of biochemical and morphological markers most probably due to increase in COC oxidative metabolism.     

Cypermethrin-induced oxidative stress in rat brain and liver is prevented by vitamin E or allopurinol

Considering that the involvement of reactive oxygen species (ROS) has been implicated in the toxicity of various pesticides, this study was designed to investigate the possibility of oxidative stress induction by cypermethrin, a Type II pyrethroid. Either single (170 mg/kg) or repeated (75 mg/kg per day for 5 days) oral administration of cypermethrin was found to produce significant oxidative stress in cerebral and hepatic tissues of rats, as was evident by the elevation of the level of thiobarbituric acid reactive substances (TBARS) in both tissues, either 4 or 24 h after treatment. Much higher changes were observed in liver, increasing from a level of 60% at 4 h up to nearly 4 times the control at 24 h for single dose. Reduced levels (up to 20%) of total glutathione (total GSH), and elevation of conjugated dienes ( approximately 60% in liver by single dose at 4 h) also indicated the presence of an oxidative insult. Glutathione-S-transferase (GST) activity, however, did not differ from control values for any dose or at any time point in cerebral and hepatic tissues. Pretreatment of rats with allopurinol (100 mg/kg, ip) or Vitamin E (100 mg/kg per day, ig, for 3 days and a dose of 40 mg/kg on the 4th day) provided significant protection against the elevation of TBARS levels in cerebral and hepatic tissues, induced by single high dose of oral cypermethrin administration within 4 h. Thus, the results suggest that cypermethrin exposure of rats results in free radical-mediated tissue damage, as indicated by elevated cerebral and hepatic lipid peroxidation, which was prevented by allopurinol and Vitamin E.     

Nephrotoxic effect of tris(2,3-dibromopropyl)phosphate on rat urinary metabolites: assessment from 13C-NMR spectra of urines and biochemical and histopathological examinations

Rats received either single oral doses of 0, 25, 50, 100 and 200 mg/kg tris(2,3-dibromopropyl)phosphate (Tris-BP) or repeated doses of 50, 100 and 200 mg/kg/day Tris-BP for 7 days. Urine was collected over a 24-hr period and subjected to 13C-NMR and biochemical examinations. Tris-BP produced significant increases of urinary glucose and lactate. Urinary gamma-glutamyltransferase, lactate dehydrogenase and alkaline phosphatase levels were significantly elevated on the first 2 days of post-treatment. Histopathologically, the kidney exhibited proximal tubular damage at a dose of 200 mg/kg. There was a good correlation among the histopathological, biochemical results, and the 13C-NMR urinary metabolite fingerprints in the assessment of Tris-BP-induced renal damage. The abnormal patterns of metabolite excretion suggested that the lesions produced by Tris-BP were caused by changes in the metabolic function of tubular epithelial cells. The urinary excretion of lactate, enzymes and inhibition of glucose reabsorption from the tubular lumina may be attributed to necrosis and desquamation of the tubular cell.     

Inhibitory effect of Emblica officinalis on the in vivo clastogenicity of benzo[a]pyrene and cyclophosphamide in mice

Benzo[a]pyrene (B[a]P) and cyclophosphamide (CP) are potent carcinogens/mutagens. Effect of Emblica officinalis extract administration on the in vivo genotoxicity of B[a]P and CP was studied using bone marrow chromosomal aberration and micronucleus induction tests in mice. Three doses (50, 250 and 500 mg/kg body weight) of the plant extract were administered orally for 7 consecutive days prior to the administration of single dose of mutagens (B[a]P 125 mg/kg oral; CP 40 mg/kg i.p.). It was found that administration of 250 and 500 mg/kg of E. officinalis extract significantly inhibited the genotoxicity of B[a]P as well as CP in both the assay systems. Administration of 50 mg/kg of the plant extract had no inhibitory effect. Vitamin C, a major constituent of E. officinalis when administered at dose level of 9 mg/kg b.w. (the approximate estimated amount present in the highest dose of plant extract, i.e. 500 mg) for 7 days did inhibit chromosomal aberrations and micronuclei induction, but not in a significant manner. Effect of administration of the abovementioned effective doses (250 and 500 mg/kg oral for 7 days) of plant extract and vitamin C (9 mg/kg oral for 7 days) on the hepatic activation and detoxification enzymes was also studied. Significant induction in the levels of glutathione content (GSH) and of antioxidant and detoxification enzymes viz., glutathione peroxidase (GPx), glutathione reductase (GR) and glutathione-S transferase (GST) resulted from plant extract treatment to animals. On the other hand, cytochrome P 450 level was significantly decreased in the plant-extract-treated animals. There was no significant change in cytochrome P 450, GSH contents and activities of enzymes on treatment with vitamin C. The data indicate that the possible mechanism of inhibition by plant extract is mediated by its modulatory effect on hepatic activation and disposition processes.     

Distribution of radio-labeled N-Acetyl-L-Cysteine in Sprague-Dawley rats and its effect on glutathione metabolism following single and repeat dosing by oral gavage

The distribution of radio-labeled N-Acetyl-L-Cysteine (NAC) and its impact on glutathione (GSH) metabolism was studied in Sprague-Dawley rats following single and multiple dosing with NAC by oral gavage. Radioactivity associated with administration of (14)C-NAC distributed to most tissues examined within 1 hour of administration with peak radioactivity levels occurring within 1 hour to 4 hours and for a majority of the tissues examined, radioactivity remained elevated for up to 12 hours or more. Administration of a second dose of 1,200 mg/kg NAC + (14)C-NAC 4 hours after the first increased liver, kidney, skin, thymus, spleen, eye, and serum radioactivity significantly beyond levels achieved following 1 dose. Administration of a third dose of 1,200 mg/kg NAC + (14)C-NAC 4 hours after the second dose did not significantly increase tissue radioactivity further except in the skin. GSH concentrations were increased 20% in the skin and 50% in the liver after one dose of 1,200 mg/kg NAC whereas lung and kidney GSH were unaffected. Administration of a second and third dose of 1,200 mg/kg NAC at 4 hours and 8 hours after the first did not increase tissue GSH concentrations above background with the exception that skin GSH levels were elevated to levels similar to those obtained after a single dose of NAC. Glutathione-S-transferase (GST) activity was increased 150% in the kidney and 10% in the liver, decreased 60% in the skin, and had no effect on lung GST activity following a single dose of 1,200 mg/kg NAC. Administration of a second dose of 1,200 mg/kg NAC 4 hours after the first decreased skin GST activity a further 20% whereas kidney GST activity remained elevated at levels similar to those obtained after 1 dose of NAC. Administration of a third dose of NAC 4 hours after the second dose increased liver GST activity significantly as compared to background but did not affect skin, kidney, or lung GST activity. Transient decreases in glutathione reductase (GR) activity were measured in the skin and kidney in association with repeat administration of 1,200 mg/kg NAC. Glutathione peroxidase (GxP) activity was increased in the skin, kidney, and liver suggesting that oxidative stress was occurring in these tissues in response to repeat dosing with NAC. Overall, the results of this study present the possibility that NAC could provide some benefit in preventing or reducing toxicity related to exposure to chemical irritants (particularly sulfur mustard) in some tissues by increasing tissue NAC and/or cysteine levels, GSH concentrations, and GST activity. However, follow-on studies in animals are needed to confirm that oral administration of single and multiple doses of NAC can significantly reduce skin, eye, and lung toxicity associated with sulfur mustard exposure. The finding that GxP activity is elevated, albeit transiently, following repeat administration of NAC suggests that repeat administration of NAC may induce oxidative stress in some tissues and further studies are needed to confirm this finding.     

Tissue distribution of 2-(2-nitro-4-trifluoromethylbenzoyl)-cyclohexane-1,3-dione (NTBC) and its effect on enzymes involved in tyrosine catabolism in the mouse

Administration of a single oral dose of 2-(2-nitro-4-trifluoromethyl-benzoyl)-cyclohexane-1,3-dione (NTBC) to mice increases the concentration of tyrosine in the plasma and aqueous humour. The tyrosinaemia is both time and dose-dependent with a single dose of 30 micromol NTBC/kg (10 mg/kg) producing maximal concentrations of tyrosine in plasma of about 1200 nmol/ml and in aqueous humour of about 2200 nmol/ml at 16 h after dosing. Analysis of the key hepatic enzymes involved in tyrosine catabolism, following a single dose of 30 micromol NTBC/kg, showed that 4-hydroxyphenylpyruvate dioxygenase (HPPD) was markedly inhibited soon after dosing and that the activity recovered very slowly. In response to the tyrosinaemia, the activity of hepatic tyrosine aminotransferase (TAT) was induced about two-fold, while the activity of hepatic homogentisic acid oxidase (HGO) was reduced at 4 and 5 days after dosing. Daily oral administration of NTBC at doses up to 480 micromol NTBC/kg (160mg/kg/day) to mice produced a maximal tyrosinaemia of about 600-700nmol/ml plasma, showing some adaptation relative to a single dose. Unlike the rat, no treatment-related corneal lesions of the eye were seen at any dose levels up to 6 weeks. Administration of a single oral dose of [14C]-NTBC at 30 micromol/kg led to selective retention of radiolabel in the liver and to a lesser extent the kidneys. Our studies show that NTBC is a potent inhibitor of mouse liver HPPD, which following repeat exposure produces a marked and persistent tyrosinaemia, which does not result in ocular toxicity.     

Effect of pretreatment with some mixed-function oxidase enzyme inducers on the acute hepatotoxicity of coumarin in the rat

Male Sprague-Dawley rats were pretreated with saline, corn oil, sodium phenobarbitone (PB) (100 mg/kg body weight/day), 20-methylcholanthrene (20 MC) (20 mg/kg body weight/day) or Aroclor 1254 (ARO) (100 mg/kg body weight/day) by daily ip injections for 5 days. Animals were then given single oral doses of either 250 or 500 mg coumarin/kg body weight and hepatotoxicity was assessed after 24 hr. Coumarin produced hepatotoxicity, which comprised hepatocyte necrosis and elevation of plasma alanine aminotransferase and aspartate aminotransferase activities, in all pretreated groups. Hepatic microsomal cytochrome P-450 levels were reduced after coumarin administration. In rats pretreated with saline, corn oil or PB, coumarin produced centrilobular hepatic necrosis, whereas in rats pretreated with 20 MC or ARO, coumarin produced periportal hepatic necrosis. These results demonstrate that mixed-function oxidase enzyme inducers can modulate acute coumarin-induced hepatotoxicity in the rat. As coumarin is known to be bioactivated by cytochrome P-450-dependent enzymes, the change in the lobular distribution of toxicity after pretreatment with 20 MC or ARO is presumably due to the induction of particular cytochrome P-450 isoenzymes in periportal hepatocytes.     

Effects of carbamazepine on hepatic glutathione level in rats and determination of carbamazepine and its epoxide metabolite in plasma by HPLC

We investigated whether carbamazepine, which is known to be metabolized to an electrophilic epoxide derivative in the body, causes any decrease, analogous to the action of epoxides, of hepatic glutathione (GSH) level in rats. Carbamazepine was administered to rats and liver GSH levels were determined spectrophotometrically. Neither a single low nor repeated low doses (30 mg/kg) of carbamazepine (CBZ) produced a statistically significant difference in GSH levels relative to controls. A single high dose of CBZ (100 mg/kg) produced a large and significant decrease relative to control (GSH level 3.82 +/- 0.64 vs 6.54 +/- 0.45 mumol GSH/g liver). CBZ and its metabolite carbamazepine-10,11-epoxide were determined in plasma by HPLC after the high dose of carbamazepine administration. The concentrations of carbamazepine and carbamazepine-10,11-epoxide were 18.9 +/- 2.9 micrograms/ml and 10.7 +/- 2.8 micrograms/ml, respectively.     

Adaptogenic and safety evaluation of seabuckthorn (Hippophae rhamnoides) leaf extract: a dose dependent study.

The effects of seabuckthorn (Hippophae rhamnoides L., Elaeagnaceae), leaf aqueous extract were examined in rats for its adaptogenic activity and toxicity. Dose dependent adaptogenic study of extract was carried out at different doses administered orally, 30min prior to cold (5 degrees C)-hypoxia (428mmHg)-restraint (C-H-R) exposure. After sub-acute toxicity studies on 10 and 20 times doses of maximal effective dose administered for 14 days (single oral dose of 1g/kg and 2g/kg once daily) and maximal effective dose administered for 30 days (single oral dose of 100mg/kg once daily), biochemical and hematological parameters were studied in the serum and blood. The maximal effective adaptogenic dose of the extract was 100mg/kg body weight. No significant changes were observed in organ weight/body weight ratios, of any vital organ studied (except liver and kidney in 1g/kg and 2g/kg body weight doses, respectively), and biochemical and hematological parameters of the sub-acute drug treated animals in comparison to control rats. In acute toxicity study LD(50) of the extract was observed to be >10g/kg when given orally. These results indicate that seabuckthorn leaf aqueous extract possess potent adaptogenic activity with no toxicity even after sub-acute (30 days) maximal effective dose administration.     

Hepatotoxicity of high oral dose (−)-epigallocatechin-3-gallate in mice

The tea polyphenol (−)-epigallocatechin-3-gallate (EGCG) has been studied for chronic disease preventive effects, and is marketed as part of many dietary supplements. However, case-reports have associated the use of green tea-based supplements with liver toxicity. We studied the hepatotoxic effects of high dose EGCG in male CF-1 mice. A single dose of EGCG (1500 mg/kg, i.g.) increased plasma alanine aminotransferase (ALT) by 138-fold and reduced survival by 85%. Once-daily dosing with EGCG increased hepatotoxic response. Plasma ALT levels were increased 184-fold following two once-daily doses of 750 mg/kg, i.g. EGCG. Moderate to severe hepatic necrosis was observed following treatment with EGCG. EGCG hepatotoxicity was associated with oxidative stress including increased hepatic lipid peroxidation (5-fold increase), plasma 8-isoprostane (9.5-fold increase) and increased hepatic metallothionein and γ-histone 2AX protein expression. EGCG also increased plasma interleukin-6 and monocyte chemoattractant protein-1. Our results indicate that higher bolus doses of EGCG are hepatotoxic to mice. Further studies on the dose-dependent hepatotoxic effects of EGCG and the underlying mechanisms are important given the increasing use of green tea dietary supplements, which may deliver much higher plasma and tissue concentrations of EGCG than tea beverages.     

Endotoxin potentiates the hepatotoxicity of cocaine in male mice

Cocaine produces hepatotoxicity by a mechanism that remains undefined but that has been linked to its oxidative metabolism. Endotoxin (lipopolysaccharide, LPS) is also a well-known cause of hepatic damage, where exposure to non-injurious doses of LPS increases the toxicity of certain hepatotoxins. This study was conducted to investigate the possible potentiation of cocaine-mediated hepatotoxicity (CMH) by LPS. Male CF-1 mice were administered oral cocaine hydrochloride for 5 consecutive days at a dose of 20 mg/kg with and without 12 x 10(6) EU LPS/kg given intraperitoneally 4 h after the last cocaine injection. Serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) were measured as markers of liver injury. Blood and liver glutathione (GSH) levels were determined, as well as the activities of glutathione peroxidase (GPx) and catalase (CAT). In addition, the activity of liver glutathione reductase (GRx) was measured. The results demonstrate that endotoxin potentiated the hepatotoxicity of cocaine. Serum ALT and AST were significantly elevated with the combined cocaine and LPS treatment versus all other treatments. While cocaine alone resulted in centrilobular necrosis, the cocaine and LPS combination produced submassive necrosis. The increased hepatic GSH content and GRx activity observed with cocaine alone were not observed with the combination treatment, rendering the liver more susceptible to oxidative stress. Moreover, there was a significant decrease in the activities of hepatic GPx and CAT, particularly with the combination treatment. In conclusion, this study demonstrates that LPS potentiates the hepatotoxicity of cocaine as revealed by an array of biochemical and morphological markers.