Glutathione depletion: its effects on other antioxidant systems and hepatocellular damage.

1. The mechanisms of the liver damage produced by three glutathione (GSH)-depleting agents, bromobenzene, allyl alcohol and diethyl maleate, were investigated. 2. With each toxin liver necrosis was accompanied by lipid peroxidation that developed only after severe depletion of GSH. 3. Changes in antioxidant systems by alpha-tocopherol (vitamin E) and ascorbic acid were studied. A decrease in the hepatic level of vitamin E, and a change in the redox state of vitamin C (increase in oxidized over reduced form) were evident whenever extensive lipid peroxidation developed. However, in the case of bromobenzene intoxication these alterations preceded lipid peroxidation, and may be an index of oxidative stress leading to subsequent membrane damage. 4. Experiments carried out with vitamin E-deficient or supplemented diets indicated that pathological phenomena occurring as a consequence of GSH depletion depend on hepatic levels of vitamin E. In vitamin E-deficient animals, lipid peroxidation and liver necrosis appeared earlier than in animals fed the control diet. In animals fed a vitamin E-supplemented diet, bromobenzene and allyl alcohol had only limited toxicity, and diethyl maleate none, in spite of similar hepatic GSH depletion. Thus, vitamin E may largely modulate the expression of toxicity by GSH-depleting agents.     

Glutathione depletion: Its effects on other antioxidant systems and hepatocellular damage

1. The mechanisms of the liver damage produced by three glutathione (GSH)-depleting agents, bromobenzene, allyl alcohol and diethyl maleate, were investigated.

2. With each toxin liver necrosis was accompanied by lipid peroxidation that developed only after severe depletion of GSH.

3. Changes in antioxidant systems by α-tocopherol (vitamin E) and ascorbic acid were studied. A decrease in the hepatic level of vitamin E, and a change in the redox state of vitamin C (increase in oxidized over reduced form) were evident whenever extensive lipid peroxidation developed. However, in the case of bromobenzene intoxication these alterations preceded lipid peroxidation, and may be an index of oxidative stress leading to subsequent membrane damage.

4. Experiments carried out with vitamin E-deficient or supplemented diets indicated that pathological phenomena occurring as a consequence of GSH depletion depend on hepatic levels of vitamin E. In vitamin E-deficient animals, lipid peroxidation and liver necrosis appeared earlier than in animals fed the control diet. In animals fed a vitamin E-supplemented diet, bromobenzene and allyl alcohol had only limited toxicity, and diethyl maleate none, in spite of similar hepatic GSH depletion. Thus, vitamin E may largely modulate the expression of toxicity by GSH-depleting agents.     

Effect of an acute dose of ethanol on lipid peroxidation in rats: action of vitamin E.

Free radical generation is an important step in the pathogenesis of ethanol-associated liver injury. Administration of ethanol induces an increase in lipid peroxidation both by enhancing the production of oxygen reactive species and by decreasing the levels of endogenous antioxidants. This work focuses on the generation of free radicals provoked by an acute ethanol dose in rats, and the role of different dietary levels of vitamin E. The objective of this investigation was to study the effect of three different dietary levels of vitamin E (deficient, control and supplemented with 20 times higher levels) on plasma and liver lipid peroxidation (assayed by TBARS), vitamin E in plasma and liver, and hepatic glutathione concentration, in rats receiving the different diets. The animals were submitted to an acute dose of ethanol (5 g/kg body weight) administered by gavage at the end of an experimental 4 week period and were sacrificed at 0, 2, 4, 8 and 24 h after ethanol administration. Dietary vitamin E caused a dose-dependent increase in liver and plasma concentration of the vitamin, but ethanol administration decreased hepatic vitamin E in all groups. TBARS concentrations were higher in liver of rats that received the deficient diet, independent of ethanol, however, liver TBARS concentrations were low in control and supplemented groups, but increased with ethanol ingestion. Glutathione levels were lowered by ethanol administration in all groups, in different times, but recovered to this original level in 24 h time. In conclusion, vitamin E deficiency alone induces liver lipid peroxidation in rats, acute administration of ethanol affect vitamin E and GSH level and maintenance of adequate or higher vitamin E levels acts as a protective factor against free radical generation.     

Dietary iron and 2,3,7,8-tetrachlorodibenzo-p-dioxin induced alterations in hepatic lipid peroxidation, glutathione content and body weight

The effects of various levels of dietary iron on hepatic lipid peroxidation (malondialdehyde [MDA] content), reduced glutathione (GSH) and GSH peroxidase (GSH-PX) activity as well as liver and body weights of female rats following TCDD administration were examined. Rats were fed diets containing deficient (6 ppm), normal (35 ppm) and supplemented (120 ppm) iron for 17, 24 and 31 days. 2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD, 40 micrograms/kg/day P.O.) in corn oil or the vehicle was given on days 9, 8 and 7 prior to sacrifice. TCDD treatment produced a 3-fold increase in hepatic MDA content in animals on normal iron diet. TCDD administration failed to increased MDA content in iron deficient animals. In the iron supplemented groups, TCDD resulted in 2.5 fold increases in lipid peroxidation. Dietary iron had no effect on hepatic GSH-PX activity. Animals on the iron deficient diet had 12-21% decreases in hepatic GSH content. TCDD administration resulted in 15-22% decreases in GSH content in animals on the control and iron supplemented diets. TCDD treatment resulted in significant decreases in body weights of animals on all 3 diets. TCDD induced lipid peroxidation appears to be iron dependent. However, the loss in body weight due to TCDD toxicity may not be dependent on lipid peroxidation.     

Vitamin E prevents buthionine sulfoximine-induced biochemical disorders in the rat

Antioxidant therapy can improve the protection and metabolic activity of cells and tissues. In this study, the effect of vitamin E administration on buthionine sulfoximine (BSO)-induced glutathione (GSH) depletion in the rat lung and liver was investigated. Hepatic GSH was depleted by intraperitoneal administration of BSO (4 mmol kg(-1)), twice a day, for 30 days to rats. We also investigated whether the lung and liver mitochondrial GSH contents were influenced by BSO administration and whether an extracellular supply of vitamin E could prevent the changes caused by BSO-mediated GSH depletion. Glutathione levels in lung and liver tissues were depleted by 47% and 60%, respectively. Depletion of hepatic and pulmonary GSH in turn causes decline in the levels of mitochondrial GSH, leading to impaired antioxidant defence function of mitochondria. Both the cytosolic and mitochondrial glutathione disulfides (GSSG) were altered during BSO treatment, and led to drastic increase in GSSG/GSH redox status. One of the experimental groups was given vitamin E (65 mg (kg diet)(-1)) mixed with rat feed. The rats fed with vitamin E were found to have partially restored GSH levels in liver and lung, diminished levels of TBARS and minimized tissue damage. The current findings suggest that the impaired glutathione and glutathione-dependent enzyme status may be correlated with the elevated lipid peroxidation and mitochondrial membrane damage and that vitamin E therapy to the BSO-administered rats prevents the above changes. However, vitamin E did not have any effect on the activity of gamma-glutamyl cysteine synthetase (gamma-GCS).     

The role of acrolein in allyl alcohol-induced lipid peroxidation and liver cell damage in mice

Male NMRI mice were fed a sucrose diet for 48 hr in order to reduce the hepatic glutathione content and to level off its diurnal variation. After administration of allyl alcohol (AA: 1.1 mmol/kg), hepatic glutathione (24.3 +/- 7.0 nmol GSH/mg protein) was almost totally lost within the first 15 min (less than 0.5 nmol GSH/mg protein). Subsequently, a massive lipid peroxidation was observed, i.e. the animals exhaled 414 +/- 186 nmol ethane/kg/hr compared to 0.9 +/- 0.8 of controls, and the hepatic TBA-reactive compounds had increased from 55 +/- 16 pmol/mg protein in controls to 317 +/- 163 after 1 hr. Concomitantly, a 40-45% loss of the polyunsaturated fatty acids (arachidonic and docosahexaenoic acid) in the liver lipids was observed. About 80% of the cytosolic alcohol dehydrogenase activity and about 50% of the microsomal P450-content were destroyed. In vivo-inhibition of alcohol dehydrogenase by pyrazole or induction of aldehyde dehydrogenase by phenobarbital abolished AA-induced liver damage as well as glutathione depletion and lipid peroxidation, while inhibition of aldehyde dehydrogenase by cyanamide made a subtoxic dose of AA (0.60 mmol/kg) highly toxic. These results strongly favour the importance of acrylic acid formation as an additional detoxification pathway. Enhanced hepatic levels of glutathione protected in vivo against the damaging effects of AA. Depletion of the liver glutathione content by phorone or diethylmaleate alone caused marginally enhanced lipid peroxidation (phorone) but not liver cell damage. Monooxygenase inhibitors (metyrapone, diethyldithiocarbamate, alpha-naphthoflavone) or an inducer (benz(a)pyrene) did not affect AA-induced toxicity. The ferric iron chelator desferoxaminemethanesulfonate prevented AA-induced lipid peroxidation and liver cell damage in vivo. In vitro, acrolein alone failed to initiate lipid peroxidation in soy bean phospholipid liposomes or in mouse liver microsomes. Thus, acrolein not only impairs the glutathione defense system but also directly destroys cellular proteins and evokes lipid peroxidation by an indirect iron-depending mechanism.     

Lipid peroxidation, protein thiols and calcium homeostasis in bromobenzene-induced liver damage

The mechanisms of bromobenzene hepatotoxicity in vivo were studied in mice. The relationships among glutathione (GSH) depletion, lipid peroxidation, loss of protein thiols, disturbed calcium homeostasis and liver necrosis were investigated. Liver necrosis (as estimated by the serum glutamate-pyruvate transaminase (SGPT) level) appeared between 9 and 12 hr and increased at 18 hr. Lipid peroxidation which was already detectable at 6 hr in some animals, increased thereafter showing a good correlation with the severity of liver necrosis. Despite a quite fast depletion of hepatic GSH, a significant decrease in protein thiols could be observed at 12-18 hr only. Loss of protein thiols in both whole liver and subcellular fractions (microsomes and mitochondria) was correlated with lipid peroxidation. Also a good inverse correlation was seen between lipid peroxidation and the calcium sequestration activity of liver microsomes and mitochondria. The treatment of mice with desferrioxamine (DFO) after bromobenzene-intoxication completely prevented lipid peroxidation, loss of protein thiols and liver necrosis in the animals sacrificed 15 hr after poisoning. When, however, the animals were examined at 24 hr, although the general correlation between lipid peroxidation and liver necrosis was held, in some animals (about 30% of the survivors) elevation of SGPT was observed in the virtual absence of lipid peroxidation. It seems likely therefore that the liver damage seen during the first phase of bromobenzene-intoxication is strictly related to lipid peroxidation. It is, however, possible that in some animals in which for some reason lipid peroxidation does not develop, another mechanism of liver necrosis unrelated to lipid peroxidation occurs at later times.     

Trialkyllead metabolism and lipid peroxidation in vivo in vitamin E- and selenium-deficient rats,as measured by ethane production

The ability of trialkyllead compounds to induce lipid peroxidation (measured by ethane production in vivo) was tested in rats fed a diet deficient in vitamin E and selenium or supplemented with 200 IU of dl-α-tocopherol or 0.6 ppm selenium supplied as sodium selenite. Trimethyllead induced lipid peroxidation in vivo to the greatest extent in vitamin E and selenium-deficient animals. Vitamin E and, to a lesser extent selenium, offered protection against this effect of trimethyllead. In the case of triethyllead, metabolism of the chemical caused the release of large amounts of ethane and ethylene, thereby preventing the use of ethane production as an index of lipid peroxidation. Such decomposition of triethyllead was lower in vitamin E and selenium-deficient animals compared to supplemented animals, and selenium in the diet promoted increased release of ethane and ethylene from triethyllead.     

Role of lipid peroxidation as a mechanism of liver injury after acetaminophen overdose in mice.

Mitochondrial oxidant stress and peroxynitrite formation have been implicated in the pathophysiology of acetaminophen-induced (AAP-induced) liver injury. Therefore, we tested the hypothesis that lipid peroxidation (LPO) might be involved in the injury mechanism. Male C3Heb/FeJ mice fed a diet high in vitamin E (1 g d-alpha-tocopheryl acetate/kg diet) for 1 week had 6.7-fold higher hepatic tocopherol levels than animals on the control diet (8.2 +/- 0.1 nmol/g liver). Treatment of fasted mice with 300 mg/kg AAP caused centrilobular necrosis with high plasma alanine aminotransferase (ALT) activities at 6 h (3280 +/- 570 U/l) but no evidence of LPO (hepatic malondialdehyde, 4-hydroxynonenal). Animals on the vitamin E diet had similar injury and LPO as mice on the control diet. To verify a potential effect of the vitamin E diet on drug-induced liver injury, animals were pretreated with a combination of phorone, FeSO4, and allyl alcohol. We observed, 2 h after allyl alcohol, massive LPO and liver cell injury in the livers of animals on the control diet, as indicated by a 32-fold increase in malondialdehyde levels, extensive staining for 4-hydroxynonenal, and ALT activities of 2310 +/- 340 U/l. Animals on the vitamin E diet had 40% lower hepatic malondialdehyde levels and 85% lower ALT values. Similar results were obtained when animals were treated for 3 days with alpha- or gamma-tocopherol (0.19 mmol/kg, ip). Both treatments reduced LPO and injury after allyl alcohol but had no effect on AAP hepatotoxicity. Thus, despite the previously shown mitochondrial oxidant stress and peroxynitrite formation, LPO does not appear to be a critical event in AAP-induced hepatotoxicity.     

Dermal intoxication of mice with bis(2-chloroethyl)sulphide and the protective effect of flavonoids

The influence of dermal application of sulphur mustard (SM) on hepatic lipid peroxidation and the protective effect of flavonoids in SM toxicity was investigated. SM applied on the skin of mice (0.25 or 0.5 LD50) depleted glutathione (GSH) in blood and liver. Malondialdehyde (MDA) levels in the liver showed an increase indicating lipid peroxidation. Administration of vitamin E or two flavonoids, gossypin (GN) and hydroxyethyl rutosides (HR) after dermal application of SM did not alter depletion of GSH but did reduce the MDA level significantly. Survival time of mice with 1 LD50 SM applied dermally was increased by GN and HR to a greater extent than by vitamin E or sodium thiosulphate probably due to one or more of the analgesic, anti-inflammatory, antihepatotoxic, antihistaminic, mast cell stabilization, lipid peroxidation inhibitory and free radical scavenging actions of the flavonoids. The present study indicates that dermally applied SM can induce lipid peroxidation and GSH depletion, and flavonoids may be beneficial in reducing the toxicity.     

Nitrofurantoin-Induced Hepatic and Pulmonary Biochemical Changes in Mice Fed Different Vitamin E Doses

Abstract: The hepatic and pulmonary effects of nitrofurantoin (40 mg/kg, intraperitoneally) were determined at 4 and 24 hr following its administration in mice fed for 10 weeks with a vitamin E sufficient, deficient or enriched diet. Liver glutathione (GSH) was reduced by nitrofurantoin at 4 hr but was unchanged 20 hr later. Nitrofurantoin did not affect liver glutathione peroxidase, glutathione reductase or superoxide dismutase activities. Liver catalase activities were decreased by nitrofurantoin at 4 hr. Lung GSH levels were increased whilst glutathione peroxidase activity was decreased at 4 and 24 hr. Lung glutathione reductase activity was reduced in certain groups. Nitrofurantoin did not affect lung superoxide dismutase, but catalase was decreased at 24 hr. Liver malondialdehyde levels were increased by nitrofurantoin in the vitamin E deficient group whilst lung malondialdehyde levels remained unchanged. Both liver and lung malondialdehyde levels were unaffected by vitamin E supplementation when compared to the vitamin E-sufficient group. These results suggest that nitrofurantoin (40 mg/kg) was deleterious to the liver and lung. Nitrofurantoin-induced lipid peroxidation was seen in vitamin E deficiency but an increase in dietary vitamin E content did not provide additional protection compared to the recommended daily allowance. The antioxidant acitivities of α-tocopherol and γ-enriched tocotrienol were similar.     

Effect of vitamin E on the balance between pro- and antioxidant activity of ascorbic acid in microsomes from rat heart, kidney and liver

The effect of the vitamin E status of membranes on the balance between pro- and antioxidant activity of ascorbic acid was studied in microsomes from rat heart, kidney and liver. Lipid peroxidation was initiated by 5 microM ferrous ions, in combination with amounts of ascorbic acid ranging from 0-4 mM. Lipid peroxidation was assessed after 1 h of incubation as production of thiobarbituric acid reactive material. It was found that the vitamin E status of the microsomal membranes had little effect on the balance between pro- and antioxidant activity of vitamin C. The sensitivity of the membranes to ferrous ions/ascorbic acid-induced lipid peroxidation, however, was highly dependent on the vitamin E content of the membranes. Vitamin E depletion, in combination with different ascorbic acid concentrations, showed that vitamin E deficiency is not an incontestable model system for enhanced sensitivity to lipid peroxidation in all organs.     

Allyl alcohol-induced hemolysis and its relation to iron release and lipid peroxidation

Allyl alcohol administration to starved mice produced, along with liver necrosis, a high incidence (about 50%) of hemolysis. A marked decrease in erythrocyte glutathione (GSH) was seen in all the intoxicated animals. Such a decrease was significantly higher in the animals showing hemolysis. In these animals a substantial amount of malonic dialdehyde (MDA) was detected in plasma and a marked decrease in arachidonic and docosahexaenoic acids was found in erythrocyte phospholipids. These data suggest that the allyl alcohol-induced hemolysis is mediated by lipid peroxidation. In vitro studies have shown that the addition of acrolein to mouse erythrocytes produces a dramatic GSH depletion, which is followed by the appearance of lipid peroxidation and, after an additional 30 min of incubation, by the development of hemolysis. Prevention of lipid peroxidation by an antioxidant (Trolox C) or an iron chelator (desferrioxamine, DFO), prevented hemolysis even if the erythrocyte GSH level was dramatically decreased. In vitro, allyl alcohol and acrylic acid were ineffective in inducing GSH depletion, lipid peroxidation and hemolysis. Studies of possible induction of lipid peroxidation in erythrocytes showed that a progressive increase in "free" (desferal chelatable) iron occurs in the erythrocytes during the incubation with acrolein. It seems, therefore, that a release of iron from iron-containing complexes occurs in acrolein-treated erythrocytes and that such "free" iron promotes lipid peroxidation.     

Potentiation of cisplatin-induced lipid peroxidation in kidney cortical slices by glutathione depletion

Effects of cis-diamminedichloroplatinum II (cisplatin), an antitumor agent with a dose-limiting effect of nephrotoxicity, on lipid peroxides and glutathione (GSH) were examined in rat kidney cortical slices treated with or without diethylmaleate (DEM), a GSH depletor, in vitro. DEM (3 mM) decreased the GSH level to about 16% of the control with a concomitant increase in lipid peroxides after 90 min of incubation. The same effects were obtained with 1 mM cisplatin 90 min later. Cisplatin (1 mM) with DEM (2 mM) stimulated both the decrease in GSH and the increase in lipid peroxides 90 min after incubation. However, cisplatin with DEM markedly stimulated lipid peroxidation with a small effect on the GSH decrease by cisplatin alone 30 min after incubation, while each drug by itself did not affect lipid peroxidation. The antioxidants N,N'-diphenyl-p-phenylene-diamine (DPPD), promethazine, and ascorbic acid abolished cisplatin-induced lipid peroxidation in the presence of DEM. DPPD had no effect on the depletion of GSH caused by cisplatin and DEM. Ascorbic acid and promethazine caused only a slight return towards the control level. The results suggested that cisplatin-induced lipid peroxidation is due to another mechanism in addition to the GSH depletion caused by the antitumor drug.     

Activation of the microsomal glutathione-S-transferase and reduction of the glutathione dependent protection against lipid peroxidation by acrolein

Allyl alcohol is hepatotoxic. It is generally believed that acrolein, generated out of allyl alcohol by cytosolic alcohol dehydrogenase, is responsible for this toxicity. The effect of acrolein in vitro and in vivo on the glutathione (GSH) dependent protection of liver microsomes against lipid peroxidation, and on the microsomal GSH-S-transferase (GSH-tr) in the rat was determined. In vitro incubation of liver microsomes with 5 mM acrolein for 30 sec resulted in a 2-fold activation of the GSH-tr. This activation probably proceeds via alkylation of the thiol group of the GSH-tr. In vivo administration of 1.1 mmol allyl alcohol/kg to rats did also result in a 2-fold stimulation of the GSH-tr activity. Administration of 375 mg pyrazole/kg, an inhibitor of the alcohol dehydrogenase, thus reducing the acrolein formation, prevented the in vivo stimulation of GSH-tr by allyl alcohol. This indicates that the activation of GSH-tr in vivo by allyl alcohol probably also proceeds via alkylation of the thiol group of the GSH-tr by acrolein. GSH protects liver microsomes against lipid peroxidation, probably via a free radical reductase that reduces vitamin E radicals at the expense of GSH. Incubating liver microsomes for 30 min with 0.1 mM acrolein reduced the GSH dependent protection against lipid peroxidation, probably because an essential thiol group(s) on the free radical reductase is alkylated. In vivo administration of allyl alcohol did not reduce the GSH dependent protection of the microsomes. Probably the thiol group(s) located on the free radical reductase is less accessible or less reactive than the thiol group on the GSH-tr. After administration of allyl alcohol we found no evidence for in vivo lipid peroxidation. Therefore we could not evaluate the importance of the GSH dependent protection against lipid peroxidation in vivo.     

Drug-induced lipid peroxidation in mice—I Modulation by monooxegenase activity,glutathione and selenium status

Feeding male mice for 2 days with sucrose leads to a decrease of total liver glutathione by more than 50 per cent when compared to controls. Such animals were intoxicated with 300 mg/kg paracetamol and upon administration of inducers of the drug-metabolizing system, in vivo and vitro lipid peroxidation in these animals was largely increased as well as the susceptibility to the drug. Pretreatment of the mice with methylcholanthrene led to a 28-fold, with benzo(α)pyrene to a 22-fold, and with phenobarbital to a tenfold increase in ethane exhalation. In vivo administration of various monooxygenase inhibitors showed that all agents effectively inhibit paracetamol-induced lipid peroxidation. It is concluded that phase I metabolism of paracetamol is a prerequisite for the manifestation of drug-induced lipid peroxidation.Selenium deficiency in mice neither affected hepatic levels of glutathione nor its decrease following sucrose feeding, nor glutathione transferase, superoxide dismutase, catalase and glutathione reductase activity. Selenium-dependent glutathione peroxidase activity of selenium-deficient mice, reactive with H₂O₂ as well as with t-butylhydroperoxide, decreased to 5 per cent of the supplemented controls. A glutathione peroxidase activity, which utilized cumenehydroperoxide as a substrate but insensitive to selenium deficiency, was found. Selenium-deficient diethylmaleate-pretreated animals were much more susceptible to paracetamol-induced lipid peroxidation than controls. Supplemented diethylmaleate-pretreated animals showed no signs of lipid peroxidation if treated with 100 mg/kg aminopyrine or ethylmorphine. However, deficient animals exhibited high ethane exhalation rates, drastically increased serum transaminases, loss of hepatic glutathione and mortality upon administration of these drugs. Qualitatively similar results with lower ethane exhalation rates were observed when 125 mg/kg furosemide was administered to diethylmaleate-pretreated selenium-deficient or -adequate mice. Even administration of 200 mg/kg ethoxycoumarin in combination with diethylmaleate lead to significant lipid peroxidation in phenobarbital-induced mice.The results demonstrate that in vivo selenium-dependent glutathione peroxidase plays a predominant role within the glutathione redox couple system. The enzyme protects the liver from peroxidative damage evoked by phase I metabolism of various drug types, as long as sufficient glutathione is available. It is suggested that activated oxygen released from the microsomal monooxygenase is the species responsible for the observed lipid peroxidation accompanied by severe acute liver lesions.     

Intestinal absorption of oxalate in scorbutic and ascorbic acid supplemented guinea pigs

Radiolabelled U-14C oxalic acid uptake was measured in the intestine of scorbutic and ascorbic acid (AA) supplemented guinea pigs. The feeding of vitamin C deficient diet to the animals for 26 days resulted in a significant fall in the ascorbic acid levels in the various tissues studied. Supplementation of vitamin C (10, 25 or 50 mg per 200 g body weight) increased ascorbic acid levels of spleen, adrenals, liver and leucocytes. The intestinal uptake of oxalate follows a passive diffusion mechanism in normally fed guinea pigs. The oxalate uptake rate was significantly increased (p less than 0.001) in the vitamin C administered group. Vitamin C depletion significantly decreased the oxalate uptake rate as compared to control animals. The changes observed in the uptake rate appear to be related with the chemical aberrations produced in the brush border membranes.     

Role of lipid peroxidation on renal dysfunction associated with glutathione depletion. Effects of vitamin E.

This study was designed to investigate the role of lipid peroxidation in the pathogenesis of renal dysfunction in glutathione (GSH)-depleted rats. Renal function parameters and acid-base status were analyzed in diethylmaleate (DEM)-treated rats previously injected with vitamin E (Vit.E). Vit.E was effective in inhibiting the elevation in renal lipid peroxidation found in GSH-depleted rats. Vit.E also ameliorated the renal response to the metabolic acidosis without modification in lactate production induced by DEM administration. The increase in sodium and water urine excretion and the diminution of the urine to plasma osmolalities ratio were not reversed in these animals. These results lead us to conclude that lipid peroxidation is associated with distal acidification impairment observed with GSH-depletion, but it is not related to the sodium reabsorption alteration in the ascending loop of Henle.     

Vitamin E and glutathione are required for preservation of microsomal glutathione S-transferase from oxidative stress in microsomes

Glutathione (GSH) inhibited lipid peroxidation induced by NADPH-BrCCl3 in vitamin E sufficient microsomes, but did not in phenobarbital (PB)-treated microsomes (containing about 60% of normal vitamin E) or in vitamin E-deficient microsomes (containing about 30% of normal vitamin E). There was a good correlation between the increased formation of CHCl3 from BrCCl3 in the presence of GSH under anaerobic conditions and the vitamin E level in the microsomes. A normal level of vitamin E in microsomes was thus very important for GSH-dependent inhibition of lipid peroxidation and for the efficient formation of CHCl3 from BrCCl3. Bromosulfophthalein (BSP) eliminated the effects of GSH on lipid peroxidation and CHCl3 formation. The apparent Km and Vmax of substrates for GSH S-transferase were changed by in vivo depletion of vitamin E in microsomes, and the Vmax/Km values were significantly reduced. The enzyme activity in microsomes was inactivated following the loss of vitamin E during in vitro lipid peroxidation, and GSH prevented the loss of vitamin E and protected the enzyme from attack by free radicals. GSH inhibited lipid peroxidation induced by NADPH-Fe2+ and the loss of GSH S-transferase activity during the peroxidation in PB-treated microsomes, but did not in the case of induction by NADPH-BrCCl3. A possible relation between the microsomal GSH S-transferase activity and defense by GSH against lipid peroxidation in microsomes is discussed.     

Lipid peroxidation: A possible mechanism of cephaloridine-induced nephrotoxicity

Cephloridine produces renal cortical injury, but the precise mechanism responsible for this nephrotoxicity remains unclear. Recently cephaloridine has been shown to deplete reduced glutathione (GSH) concentration selectively in renal cortex. Cephaloridine nephrotoxicity can be potentiated by diethyl maleate (a GSH depletor), but no glutathione conjugate can be detected. Thus, it was of interest to investigate further the mechanism of depletion of renal cortical GSH by cephaloridine. In the present study, cephaloridine markedly decreased GSH in rat and rabbit renal cortex while concomitantly increasing oxidized glutathione (GSSG). Furthermore, cephaloridine increased lipid peroxidation specifically in renal cortical cells. Conjugated diene formation (an index of lipid peroxidation) was increased in renal cortex but not in the liver shortly following administration of cephaloridine. Removal of selenium and/or vitamin E from the diet, which should enhance lipid peroxidation, potentiated cephaloridine nephrotoxicity and enhanced cephaloridine-induced morphological damage in the kidney. These findings are consistent with a major role of lipid peroxidation in the etiology of cephaloridine nephrotoxicity.