Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “GLUTATHIONE”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 397 records · Page 22Linked to original sources
PubMed1990

Glutathione S-transferase and glutathione peroxidase expression in normal and tumour human tissues.

Glutathione S-transferases play a central role in drug detoxification and have been implicated in the sensitivity of tumour cells to anticancer drugs. In this study, glutathione S-transferase (GST) isozyme expression in normal and tumour tissue from human lung, colon, stomach, breast, kidney and liver tissue has been quantified using sensitive and subunit specific radioimmunoassays (RIA), together with Western blot analysis and measurement of substrate metabolism. Glutathione S-transferase pi was the predominant GST in the majority of the tumours examined. The concentration of this enzyme was increased significantly in tumour tissue relative to normal lung, colon, and stomach tissue. A strong correlation was observed (r = 0.77, P less than 0.01) between GST activity and GST pi levels in those tumour samples. The concentrations of the alpha class GST, the predominant isoenzymes in normal stomach, kidney and liver, decreased dramatically in tumour tissue from these organs. Western blot analysis revealed the presence of novel polypeptides that cross-reacted with antisera raised against alpha and mu class GST. Our data demonstrates that although GST pi is the predominant GST isoenzyme in many tumours, significant levels of the other GST subunits are also present and collectively can represent a significant proportion of the GST content. Therefore the properties of all the GST isoenzymes need consideration when assessing the role of these proteins in drug resistance. Selenium-dependent glutathione peroxidase, an enzyme activity also implicated in the mode of action of certain antitumour agents, was also studied and shown to be the predominant glutathione-dependent peroxidase in all tumours except the hepatoma.

Blotting, Western↗
PubMed1989

Studies on the active site of rat glutathione S-transferase isoenzyme 4-4. Chemical modification by tetrachloro-1,4-benzoquinone and its glutathione conjugate.

The active site of glutathione S-transferase isoenzyme 4-4, purified from rat liver, was studied by chemical modification. Tetrachloro-1,4-benzoquinone, a compound previously shown to inactivate glutathione S-transferases very efficiently by covalent binding in or close to the active site, completely prevented the alkylation of the enzyme by iodoacetamide, indicating that the reaction had taken place with cysteine residues. Both from radioactive labeling and spectral quantification experiments, evidence was obtained for the covalent binding of three benzoquinone molecules per subunit, i.e. equivalent to the number of cysteine residues present. This threefold binding was achieved with a fourfold molar excess of the benzoquinone, illustrating the high reactivity of this compound. Comparison of the number of amino acid residues modified by tetrachloro-1,4-benzoquinone with the decrease of catalytic activity revealed an almost complete inhibition after modification of one cysteine residue. Chemical modification studies with diethylpyrocarbonate indicated that all four histidine residues of the subunit are ethoxyformylated in an at least partially sequential manner. Modification of the second histidine residue resulted in complete loss of catalytic activity. Preincubation of the transferase with the glutathione conjugate of tetrachloro-1,4-benzoquinone resulted in 78% protection against this modification. However, glutathione itself hardly protected against the reaction with diethylpyrocarbonate. The intrinsic fluorescence properties of the enzyme were affected by covalent binding of tetrachloro-1,4-benzoquinone. The concentration dependency of the fluorescence quenching is strongly correlated with the inactivation of the enzyme, indicating that covalent binding of the benzoquinone occurs in the vicinity of at least one tryptophan residue. Finally, the binding of bilirubin, as measured by means of circular dichroism, was inhibited by preincubation of the enzyme with tetrachloro-1,4-benzoquinone in a manner which strongly correlated with the loss of enzymatic activity, the protection against inactivation by diethylpyrocarbonate, and the fluorescence quenching. All processes showed a 70-80% decrease after incubation of the enzyme with an equimolar amount of the benzoquinone. Thus, evidence is presented for the presence of a cysteine, a histidine and a tryptophan residue in, or in the vicinity of, the active site of the glutathione S-transferase 4 subunit.

Animals↗
PubMed1985

Glutathione reductase is not required for maintenance of reduced glutathione in Escherichia coli K-12.

Seven independently isolated glutathione reductase-deficient (gor) Escherichia coli mutants were found to have an in vivo glutathione redox state that did not significantly differ from that of the parental strain, 98 to 99% reduced. Strains containing both a gor mutation and either a trxA mutation (thioredoxin deficient) or a trxB mutation (thioredoxin reductase deficient) were able to maintain a 94 to 96% reduced glutathione pool, suggesting that glutathione can be reduced independently of glutathione reductase and thioredoxin reductase.

Escherichia coli↗
PubMed1975

Analyses in blood of dermatological patients. I. Glutathione and glutathione reductase.

Glutathione was estimated in 98 blood samples from dermatological patients; in only two cases, both of contact eczema, a value considerably below normal was found. Glutathione reductase was assayed in blood samples from 139 different patients and 21 normal controls. The activity was significantly higher in atopic dermatitis (17 patients). A significantly greater variable was found among patients with non methotrexate-treated psoriasis (44), light sensitivity (12) and scleroderma (5). In the methotrexate-treated psoriatic group (24) and mean and variability did not differ significantly from normal. In most hospitalized patients a low glutathione reductase activity rose within a few weeks, but in a case of dermatitis herpetiformis a very low level persisted for 3 months. Blood samples with very low glutathione reductase activity, taken from a case of psoriasis and from a patient on griseofulvin treatment, gave a positive peroxide test and tended to hemolyze; these returned to normal together with the glutathione reductase activity.

Adolescent↗
PubMed1984

Biliary excretion of glutathione and glutathione disulfide in the rat. Regulation and response to oxidative stress.

Regulation of the biliary excretion of reduced glutathione (GSH) and glutathione disulfide (GSSG) and responses to selected model toxins were examined in male Sprague-Dawley rats. In control and phenobarbital-pretreated rats in which the intrahepatic concentration of GSH was modulated by the administration of diethyl maleate or acetaminophen, the biliary concentration of GSH was consistently lower than, but directly proportional to, the intrahepatic concentration of GSH. Furthermore, increments in bile flow produced by the infusion of sulfobromophthalein (BSP)-glutathione were associated with proportional increases in the biliary excretion of GSH, suggesting that GSH passes into bile passively along a concentration gradient. In contrast, GSSG appears to be secreted into bile against a steep concentration gradient. An increased hepatic production and biliary excretion of GSSG resulted from the administration of t-butyl hydroperoxide. Measurement of biliary GSSG and BSP during a constant infusion of the GSH adduct of BSP indicated that GSSG shares a common excretory mechanism with GSH adducts. Diquat, nitrofurantoin, and paraquat also markedly stimulated the biliary excretion of GSSG. On a molar basis, these compounds generated much more GSSG than a direct substrate for glutathione peroxidase such as t-butyl hydroperoxide, indicating that the compounds undergo redox-cycling with concomitant production of hydrogen peroxide. Aminopyrine (0.8 mmol/kg) also significantly increased biliary GSSG. This increase, however, was associated with a proportional increase in bile flow and in the biliary excretion of GSH such that the GSSG/GSH ratio in bile did not change. Acetaminophen and chloroform, two compounds generating electrophilic metabolites that deplete intrahepatic GSH, led to a progressive decrease in the biliary excretion of GSH and GSSG. Furosemide and dimethylnitrosamine, the electrophilic metabolites of which do not deplete hepatic GSH, minimally altered biliary GSH and GSSG. Similarly, carbon tetrachloride and iproniazid, which yield organic radical metabolites that can peroxidize membrane lipids, did not increase the biliary excretion of GSSG. This finding indicates that membrane-bound lipid hydroperoxides may not be good substrates for glutathione peroxidases. The measurement of the biliary excretion of GSSG and of the GSSG/GSH ratio in bile is a sensitive index of oxidative stress in vivo and thus complements other in vivo parameters for the study of reactive intermediates of xenobiotics such as the determination of covalent binding, the formation of lipid hydroxy acids, and the depletion of intracellular GSH.

Acetaminophen↗
PubMedDate not supplied

Biochemical parameters as biomarkers for the early recognition of environmental pollution on Scots pine trees. II. The antioxidative metabolites ascorbic acid, glutathione, alpha-tocopherol and the enzymes superoxide dismutase and glutathione reductase.

Field investigations with Scots pine trees (Pinus sylvestris L.) were performed in eastern Germany, where ambient SO2, NOx and O3 concentrations differed significantly in 1992-99 at three sites, namely Neuglobsow (yearly mean SO2 in 1992: 9 microg m(-3)), Taura (yearly mean SO2 in 1992: 54 microg m(-3)) and Rösa (yearly mean SO2 in 1992: 73 microg m(-3)). To investigate the effects of SO2, NOx and O3 on antioxidants (superoxide dismutase, ascorbic acid, glutathione, glutathione reductase, alpha-tocopherol) and pigments including chlorophyll fluorescence as well as visible damage symptoms in the form of needle yellowing and tip necroses, needles of the 1st and 2nd age class from young and mature trees were collected at the sites every October. Eight years after the start of the field study in 1992, the ambient SO2 concentrations had decreased significantly at Neuglobsow (yearly mean SO2 in 1999: 4 microg m(-3)), Taura (yearly mean SO2 in 1999: 5 microg m(-3)) and Rösa (yearly mean SO2 in 1999: 5 microg m(-3)). NOx and O3 differed less at the three sites and showed no temporal variations. Whole needle glutathione continuously decreased, although concentrations were higher in needles of the 1st and 2nd age class from the polluted sites Taura and Rösa than the unpolluted site Neuglobsow. The activities of glutathione reductase exhibited the same site-related differences and temporal variations and were correlated with concentrations of oxidized glutathione (GSSG). In contrast, the activities of the enzyme superoxide dismutase and the concentrations of whole needle ascorbic acid remained unchanged over the period. Only at the end of the investigation period did the concentrations of oxidized ascorbic acid (dehydroascorbate) increase in six-month-old needles at the polluted sites Taura and Rösa. Despite the clear decreases in SO2, the visible symptoms of needle tip necroses remained unchanged, especially at the polluted sites Taura and Rösa, although the needles contained higher pigment concentrations than needles from the unpolluted sites. The results of measurements with antioxidants as biomarkers for SO2-mediated stress in pine needles show that the adult Scots pine trees at the polluted sites suffered from greater oxidative stress than the needles from the less polluted site.

Ascorbic Acid↗
PubMed1991

Thermal inactivation study of glutathione peroxidase and glutathione reductase activities in lenses of primates and non-primates.

Heat lability studies of glutathione peroxidase and glutathione reductase activities were conducted on rabbit, sheep, rat, human, galago, cat and rhesus monkey lens supernatants. These species represent five mammalian orders. Incubation periods were 10.0 minutes in duration, with temperatures ranging from 25-100 degrees C (depending on which enzyme was being investigated). Results obtained for glutathione peroxidase activity demonstrated nearly identical heat lability profiles for human and rhesus monkey lenses. Both species were extremely labile to heat, losing activity at 30 degrees C and becoming totally inactive at temperatures of 50 degrees C (rhesus monkey) and 55 degrees C (human). Their profiles were very dissimilar to those of the other five species investigated, providing evidence for the existence of an evolutionary break. Glutathione reductase activity was extremely stable under conditions of highly elevated temperature for all seven species investigated. The human lens enzyme, the most stable of the species, maintained nearly 100% of its original activity up to 65 degrees C. Lenticular glutathione reductase activity did not reach zero levels in any of the seven species until a temperature of at least 80 degrees C was attained.

Animals↗
PubMed1994

The effects of age on glutathione peroxidase and glutathione reductase activities in lenses of Old World simians and prosimians.

The effects of age on the activities of the two enzymes of the glutathione redox cycle, glutathione peroxidase and glutathione reductase, were studied in lenses of primates. Three species were Old World simians (orangutan, olive baboon and pigtail monkey) and two were prosimians (galago and mouse lemur). Glutathione peroxidase activity of the olive baboon lens increased steadily with age while that of the pigtail monkey increased during the first 6-8 years and then plateaued. Enzyme activity in the orangutan increased steadily from 9 months to 28 years. This enzyme activity decreased steadily in the galago but increased only slightly in the mouse lemur lens. The lenticular glutathione reductase activity profiles showed decreases with age for all three simian species. Enzyme activity in the galago decreased gradually from birth to the age of 16.5 years. The enzyme activity values of the mouse lemur lens did not yield a comprehensible pattern. Lens weight increased with age in all five primate species, particularly in the infant and juvenile years and leveled off in adulthood. The current investigation demonstrated that the responses of these enzyme activities to aging were very different in Old World simians as compared to prosimians. These studies are consistent with earlier enzyme activity and thermolability data and are indicative of probable critical differences in the primary structures of the enzymes between the two primate groups.

Aging↗
PubMedDate not supplied

[Activity of glutathione reductase and glutathione-S-transferase in rabbit brain tissue in the long-term post-traumatic period].

The glutathione-reductase and glutathione-S-transferase activities in the cortex and brain stem tissues of rabbits with post-traumatic epileptic reality (1 year after the light brain injury) was defined. An increase of glutathione-reductase activity in the cortex microsomal and stem mitochondrial fractions, and increase of glutathione-S-transferase activity in cortex and stem mitochondrial fractions was obtained. The conclusion is made that the activation of the anti-oxidant glutathione fermentative system is a long-term metabolic CNS adaptation in the case while mitochondrial oxidation and oxidative phosphorilation are disturbed.

Adaptation, Physiological↗
PubMed2003

Selenium, glutathione and glutathione peroxidases in blood of patients with chronic liver diseases.

Disturbances in the antioxidant system could play a role in pathogenesis of chronic liver disease. The aim of our study was to evaluate the levels/activities of antioxidants in blood of patients with chronic liver disease. We estimated selenium and glutathione concentrations and glutathione peroxidase activities in blood of 59 patients with chronic hepatitis B or C virus infection (group 1) and 64 patients with alcoholic, autoimmune or cryptogenic chronic liver disease (group 2). The results were compared with 50 healthy controls. Whole blood and plasma selenium and red cell glutathione concentrations were significantly lower in the patients compared with the controls. Red cell glutathione peroxidase activity was slightly reduced in both subgroups of group 1 and in group 2 with normal alanine aminotransferase values. Plasma glutathione peroxidase activity was slightly but significantly higher in patients with elevated aminotransferase values. The findings suggest that disturbances in antioxidant parameters in blood of patients with chronic liver disease may be the cause of the peroxidative damage of cells.

Adolescent↗
PubMed1999

Influence of cadmium intoxication on hepatic lipid peroxidation, glutathione level, and glutathione S-transferase and gamma-glutamyl transpeptidase activities: correlation with chromosome aberrations in bone marrow cells.

We examined whether there was any correlation between chromosome aberrations (CAs) in bone marrow cells with hepatic lipid peroxidation (LPO), reduced glutathione (GSH) level, glutathione S-transferase (GST), and gamma-glutamyl transpeptidase (GGT) activity after cadmium (Cd) intoxication in both a dose- and a time-dependent manner. Cadmium chloride was administered subcutaneously in doses of 0.5, 1.5, 2.5, and 5.0 mg/kg body weight to Swiss albino Balb/c male mice. The animals were exposed for 8, 16, and 24 days, i.e., 4, 8, and 12 doses, respectively. Biochemical parameters were measured in hepatic tissue for a correlation with chromosome aberrations in bone marrow. With the increment of dose and advancement of time points, the biochemical, as well as the cytogenetic, parameters altered significantly. Hepatic lipid peroxidation and GGT activity increased significantly along with an increased percentage of chromosome aberrations in the bone marrow, but the hepatic reduced glutathione level and GST activity were found to decrease following Cd administration. Up to 5.0 mg Cd/kg body weight, lipid peroxidation did not exhibit threshold levels of toxicity as shown by the two-way (fixed effect) analysis of variance test. In contrast, the observed values of reduced glutathione levels, GST and GGT activity, and chromosome aberrations in bone marrow showed threshold activity levels. Therefore, there might be a relationship between an increase in the frequency of chromosome aberrations, elevated lipid peroxidation, and depleted glutathione levels and GST and GGT activity. The clastogenic efficacy of Cd may be mediated through the biochemical pathways.

Animals↗
PubMed1986

Differences in stereoselectivity and catalytic efficiency of three human glutathione transferases in the conjugation of glutathione with 7 beta,8 alpha-dihydroxy-9 alpha,10 alpha-oxy-7,8,9,10-tetrahydrobenzo(a)pyrene.

The kinetics of the enzyme-catalyzed conjugation of glutathione with (+/-)-7 beta, 8 alpha-dihydroxy-9 alpha, 10 alpha -oxy-7,8,9,10 -tetrahydrobenzo(a)pyrene [(+/-)-anti-BPDE] have been studied with the following human cytosolic glutathione transferases: the basic (alpha-epsilon) and near-neutral (mu) isoenzymes from liver, and the acidic (pi) isoenzyme from placenta. When the BPDE concentration was varied (using 5 mM glutathione) the apparent Vmax values for transferases alpha-epsilon, mu, and pi were 38, 570, and 825 nmol X mg-1 X min-1, respectively, with corresponding apparent Km values of 88, 27, and 54 microM. The apparent Km values for glutathione [using 80 microM (+/-)-anti-BPDE] were 0.4, 0.7, and 0.1 mM for transferase alpha-epsilon, mu, and pi, respectively. The glutathione conjugates formed with the two enantiomers of (+/-)-anti-BPDE were resolved by high performance liquid chromatography. The percentages of conjugates derived from the highly carcinogenic (+)-enantiomer were 59, 60, and greater than or equal to 90% for transferases alpha-epsilon, mu, and pi, respectively. The separate enantiomers of anti-BPDE were assayed in experiments with transferases mu and pi. Both enantiomers were substrates for transferase mu, but only the (+)-enantiomer gave measurable activity with transferase pi. A 3-fold increase in Vmax and Km values for transferase pi was obtained with (+)-anti-BPDE as compared with the racemic substrate and could be quantitatively accounted for by the finding that (-)-anti-BPDE serves as a competitive inhibitor for transferase pi.

7,8-Dihydro-7,8-dihydroxybenzo(a)pyrene 9,10-oxide↗
PubMed1977

[Effect of sarcolysine on glutathione peroxidase and glutathione reductase activity in sarcoma C-45].

A drop of glutathione peroxidase and glutathione reductase activity was revealed in sarcoma C-45 at the period of its most intensive growth. Repeated sarcolysine injections (1.2 mg/kg, intraperitoneally) caused a sharp fall in the activity of both enzymes with a simultaneous reduction of the ratio of glutathione reductase and glutathione peroxidase activities. The important role of the glutathione enzyme redox system in the realization of antitumour action of the chemotherapeutic drugs is supposed.

Animals↗
PubMed1994

Effects of oxidized glutathione and reduced glutathione on the barrier function of the corneal endothelium.

The protective effects of oxidized glutathione (GSSG) and reduced glutathione (GSH) in the irrigating solution based on BSS plus composition (Santen, Osaka, Japan), which is without GSSG (glutathione-free control solution) were compared on rabbit corneal endothelial barrier function. Corneal barrier function was evaluated by determining the effects of GSSG and GSH on carboxyfluorescein permeability (P(ac)). In a solution containing 0.3 mM GSSG (BSS plus), the P(ac) was significantly inferior to that of its paired glutathione-free control solution. With 0.6 mM GSH, the P(ac) was not different from that of its paired glutathione-free control solution. The P(ac) of the endothelium with 0.3 mM GSSG was significantly inferior to that of paired corneas exposed isolated to 0.6 mM GSH. These results show that the barrier function of the rabbit corneal endothelium is better maintained by supplementing the perfusion solution with 0.3 mM GSSG rather than 0.6 mM GSH.

Animals↗
PubMed1994

Involvement of human glutathione S-transferase isoenzymes in the conjugation of cyclophosphamide metabolites with glutathione.

Alkylating agents can be detoxified by conjugation with glutathione (GSH). One of the physiological significances of this lies in the observation that cancer cells resistant to the cytotoxic effects of alkylating agents have higher levels of GSH and high glutathione S-transferase (GST) activity. However, little is known about the GSH-/GST-dependent biotransformation of alkylating agents, including cyclophosphamide. Cyclophosphamide becomes cytostatic after the enzymatic formation of 4-hydroxycyclophosphamide. The ultimate alkylating species formed from cyclophosphamide is phosphoramide mustard. In this paper we describe the involvement of purified human glutathione S-transferases isoenzymes GST A1-1, A2-2, M1a-1a, and P1-1 in the formation of two types of glutathionyl conjugates of cyclophosphamide, i.e., 4-glutathionylcyclophosphamide (4-GSCP) and monochloromonoglutathionylphosphoramide mustard. When 0.1 mM 4-hydroxycyclophosphamide and 1 mM GSH was incubated in the presence of 10 microM GST A1-1, A2-2, M1a-1a, and P1-1 the formation of 4-GSCP was 2-4-fold increased above the spontaneous level. Enzyme kinetic analysis demonstrated the lowest Km (0.35 mM) for GST A1-1. Km values for the other GST enzymes ranged from 1.0 to 1.9 mM. Glutathione S-transferase A1-1 (40 microM) also increased the conjugation of phosphoramide mustard and GSH (both 1 mM) 2-fold, while the other major human isoenzymes, A2-2, M1a-1a, and P1-1, did not influence the formation of monochloromonoglutathionylphosphoramide mustard. These results indicate that only one enzyme within the class of human GST alpha enzymes was able to catalyze the reaction of the aziridinium ion of phosphoramide mustard with glutathione. Thus increased levels of GST A1-1 in tumor cells can contribute to an enhanced detoxification of phosphoramide mustard and hence to the development of drug resistance. Since all of the human GSTs tested did catalyze the formation of 4-GSCP, the role of 4-GSCP either as a transport form of activated cyclophosphamide or as a detoxification product is discussed.

Biotransformation↗
PubMed1997

Product of the Schistosoma mansoni glutathione peroxidase gene is a selenium containing phospholipid hydroperoxide glutathione peroxidase (PHGPx) sharing molecular weight and substrate specificity with its mammalian counterpart.

In the blood fluke Schistosoma mansoni a functionally active, monomeric, phospholipid hydroperoxide glutathione peroxidase (PHGPx) has been purified and characterized. This enzyme contains a catalytically active selenocysteine. The protein has been shown to be the product of a cloned gene, previously referred to as a glutathione peroxidase gene. S. mansoni PHGPx has been found 5 times more abundant in female than in male worm extract. As in vertebrate PHGPx, homology alignment indicates that the residues involved in the glutathione binding by the tetrametric cellular glutathione peroxidase are mutated in the S. mansoni enzyme. Thus, this aspect appears a landmark of the PHGPx-type of glutathione peroxidases, which might be of functional relevance.

Amino Acid Sequence↗
PubMed1997

Spatial distribution of glutathione, glutathione-related and antioxidant enzymes in cultured mouse embryos.

The present study was undertaken to evaluate the detoxifying capacity of organogenesis-stage murine concepti cultured in vitro. Investigative attention was particularly focused on the embryonic tissue distribution of cytoprotective pathways. Glutathione (GSH) status, GSH-related and antioxidant enzymes were assayed in the embryo proper (EP), visceral yolk sac (VYS) and ectoplacental cone (EC) of 29.44 +/- 1.56 (mean +/- SD) somite pairs concepti. All the tissues displayed significant and comparable concentrations of GSH, further supporting this tripeptide as critical in protection against embryotoxicants. The totality of enzymatic activities was detectable in the selected embryonic compartments. In terms of spatial distribution analysis, maximal activities were found in EC (glutathione peroxidase, glutathione reductase, superoxide dismutase and glyoxalase I and II), and VYS (glutathione transferase and catalase). These results indicate: (1) the organogenesis-stage conceptus, in addition to significant amounts of GSH, expresses constitutive activities of GSH-related and antioxidant enzymes; (2) maximal activity levels are detectable in the embryonic sites which, at the developmental stage selected for assay, serve (VYS) or are evolving to serve (EC) embryo/maternal exchange, and thus represent the primary sites of interaction with foreign compounds.

Animals↗
PubMed1983

Species difference in glutathione level and glutathione related enzyme activities in rats, mice, guinea pigs and hamsters.

Total glutathione (GSH and GSSG) level, and the activities of gamma-glutamylcysteine synthetase, gamma-glutamyltranspeptidase (gamma-GTP), glutathione S-transferase (GST), glutathione peroxidase (GSH-Px) and glutathione reductase (GR) in the liver were investigated in rats, mice, guinea pigs and hamsters. Hepatic GSH level in rats, mice, guinea pigs and hamsters were 7.1, 7.8, 3.5 and 5.4 mM, respectively. The lower level of GSH in guinea pigs seems to be in part attributed to the higher activity of hepatic gamma-GTP, an enzyme which catalyzes GSH breakdown. Moreover, a marked species difference in the activities of GST, GSH-Px and GR was also observed. A 48 h-fasting resulted in a decrease of GSH and GSSG levels in rats, mice and guinea pigs, but not in hamsters. In addition, both nicotineamide adenine dinucleotide phosphate- and ascorbate-dependent lipid peroxidation produced by 9000 X g supernatant fraction in fasted animal species occurred most highly in the rat followed by hamster and guinea pig, and almost undetectable in mice. Thus, it suggests that the occurrence of lipid peroxidation in fasted animals may not be related to the hepatic GSH level, and rather, a lack of occurrence of lipid peroxidation in fasted mice may be due to the increased activity of GSH-Px activity.

Animals↗