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PubMed1992

Reversed-phase chromatographic method for specific determination of glutathione in cultured malignant cells.

A chromatographic method for the specific determination of glutathione in malignant cell lines is described. The method is based on the ability of glutathione-S-transferase to specifically and quantitatively conjugate glutathione to 1-chloro-2,4-dinitrobenzene and chromatographic quantitation of the resultant conjugate, dinitrophenyl-S-glutathione, by reversed-phase liquid chromatography. The assay can be performed on 20,000 g supernatants of cell homogenates without acid extraction. 2-Mercaptoethanol, a sulfhydryl compound often used as a thiol-protective agent to preserve enzymatic activities of a number of enzymes, did not interfere with glutathione determination by this method. The dinitrophenyl-S-glutathione isolated from either standard glutathione samples or from cell homogenates was shown to be identical to authentic dinitrophenyl-S-glutathione using mass spectrometry. Recovery of glutathione in standard samples by the current method was identical to that determined using 5,5'-dithiobis(2-nitrobenzoic acid). Exogenous glutathione added to supernatants of cell homogenate in the presence or absence of 2-mercaptoethanol was also completely recovered.

Chromatography, High Pressure Liquid↗

PubMed2005

Depressed glutathione synthesis precedes oxidative stress and atherogenesis in Apo-E(-/-) mice.

Glutathione is a vital intracellular antioxidant. The enzymes involved in its synthesis and utilisation are tightly regulated, but the importance of glutathione regulation in atherogenesis is poorly understood. Here, we establish that glutathione is severely (approximately 80%) depleted very early (10 weeks) in the atheroma-prone aortic arch of male apoprotein E-deficient (Apo-E(-/-)) mice compared to age-matched wild-type controls. Importantly, this event pre-empts lipid peroxidation and detectable atheroma by several months. Depletion of glutathione was associated with excessive oxidant burden and reduced transcription and activity of the rate-limiting enzyme for glutathione synthesis, gamma-glutamylcysteine ligase, together with the glutathione-dependent antioxidant enzyme, glutathione peroxidase. Depletion via reduced synthesis of glutathione precedes lipid peroxidation and atherogenesis in Apo-E(-/-) mice. We suggest that glutathione deficiency is central to the failure of the intracellular antioxidant defences and is causally implicated in the pathogenesis of atherosclerosis. Modification of the glutathione pathway may present a novel and important therapeutic target in the prevention and treatment of atherosclerosis.

Animals↗

PubMed2003

Effects of aging and cyclosporin treatment on the hepatobiliary efflux of glutathione.

The aim of this study was to investigate the effects of cyclosporin (CyA) treatment on biliary glutathione efflux in rats of different ages (1, 2, 4, and 24 months). CyA treatment reduced the liver content of total glutathione in 1-, 2- and 24 month old rats (-30%, -43% and -30%, respectively). By contrast, oxidized glutathione (GSSG) concentration in liver tended to increase, although non significantly, in the rats aged 4 and 24 month (+36% and +28%, respectively). The oxidized-to-reduced glutathione ratio was significantly increased in 2-, 4- and 24 month old animals (+23%, +36% and >100%, respectively). Regarding biliary glutathione, our data indicate that efflux rates of total glutathione in control (untreated) rats increased to a maximum at 4 months, and decreased (-56%) in 24 month old rats, although values were still higher than those from young animals. CyA treatment significantly reduced biliary glutathione secretion except in 24 month old rats (-98%, -66% and -32%, at 1, 2 and 4 month, respectively). In addition, following inhibition of the intrabiliary catabolism of the tripeptide by acivicin, glutathione efflux rates into bile were significantly reduced by the drug only in 1- and 2 month old rats (-29% and -55%, respectively) and even tended to increase, although non significantly, in oldest animals. Our data indicate that inhibition of biliary glutathione efflux by CyA was greater in younger rats and support the view that increased intrabiliary catabolism of the tripeptide and inhibition of its canalicular transport could contribute to the decline in biliary glutathione secretion induced by the drug.

Aging↗

PubMed1998

Glutathione transferase zeta-catalyzed biotransformation of dichloroacetic acid and other alpha-haloacids.

Dichloroacetic acid (DCA) is a common drinking-water contaminant, is hepatocarcinogenic in rats and mice, and is a therapeutic agent used clinically in the management of lactic acidosis. Recent studies show that glutathione transferase Zeta (GSTZ) catalyzes the oxygenation of DCA to glyoxylic acid [Tong et al. (1998) Biochem. J. 331, 371-374]. In the present studies, the substrate selectivity of GSTZ, the kinetics of DCA metabolism, and the fate of DCA and glutathione were investigated. The results showed that GSTZ catalyzed the oxygenation of bromochloro-, bromofluoro-, chlorofluoro-, dibromo-, and dichloroacetic acid, but not difluoroacetic acid, to glyoxylic acid. GSTZ also catalyzed the biotransformation of fluoroacetic acid to S-(carboxymethyl)glutathione, and of (R,S)-2-bromopropionic acid, (R)-, (S)-, and (R,S)-2-chloropropionic acid, and (R, S)-2-iodopropionic acid, but not (R,S)-2-fluoropropionic acid, to S-(alpha-methylcarboxymethyl)glutathione; and of 2, 2-dichloropropionic acid to pyruvate. No biotransformation of 3, 3-dichloropropionic acid was detected, and no GSTZ-catalyzed fluoride release from ethyl fluoroacetate and fluoroacetamide was observed. The relative rates of DCA biotransformation by hepatic cytosol were mouse > rat > human. Immunoblotting showed the presence of GSTZ in mouse, rat, and human liver cytosol. 13C NMR spectroscopic studies showed that [2-13C]glyoxylic acid was the only observable, stable metabolite of [2-13C]DCA. Also, glutathione was required, but was neither consumed nor oxidized to glutathione disulfide, during the oxygenation of DCA to glyoxylic acid. These results are consistent with a reaction mechanism that involves displacement of chloride from DCA by glutathione to afford S-(alpha-chlorocarboxymethyl)glutathione, which may undergo hydrolysis to give the hemithioacetal S-(alpha-hydroxycarboxymethyl)glutathione. Elimination of glutathione from the hemithioacetal would give glyoxylic acid.

Animals↗

PubMed1993

Glutathione S-transferases in esophageal cancer.

Glutathione content and glutathione S-transferase enzyme activity as well as isoenzyme composition were studied in normal gastric cardia, normal squamous esophageal epithelium and corresponding malignant tumor of 10 patients with esophageal cancer. Mean values of glutathione (38 +/- 6 versus 36 +/- 12 nmol/mg protein) and glutathione S-transferase activity (532 +/- 44 versus 532 +/- 108 nmol/min mg protein) did not differ significantly between normal esophageal and tumor tissue. However, great individual differences exist. In two patients, glutathione S-transferase activity was much higher in the tumor (1081 and 1381 nmol/min mg protein) due to overexpression of class alpha, mu and pig glutathione S-transferases in one case, and of class mu and pi in the other case. In the other patients, glutathione S-transferase activity was equal (one case) or lower (seven cases) in the tumor. In normal gastric cardia glutathione content as well as glutathione S-transferase activity was significantly lower as compared to normal esophageal epithelium. In conclusion, in contrast to other gastrointestinal tumors, glutathione S-transferases are overexpressed in esophageal tumors in only a limited number of patients.

Adult↗

PubMed1998

Enterococcus faecalis glutathione reductase: purification, characterization and expression under normal and hyperbaric O2 conditions.

Glutathione reductase is found ubiquitously in eukaryotes and Gram-negative bacteria, and plays a significant role in bacterial defense against oxidative stress. Glutathione reductase from the Gram-positive bacterium Enterococcus faecalis was purified to homogeneity using anion exchange, hydrophobic interaction, and affinity chromatography. The homogeneous 49-kDa enzyme contained 1 mol bound FAD per subunit. The determined N-terminal amino acid sequence of the E. faecalis enzyme displays significant identity with glutathione reductases from other Gram-negative and Gram-positive bacteria, as well as yeast and human erythrocyte reductases. The kinetic mechanism is ping-pong, and the determined kinetic parameters exhibited by the E. faecalis glutathione reductase are similar to those found for glutathione reductases from yeast, Escherichia coli, and human erythrocyte. A two-fold increased expression of glutathione reductase activity and a three-fold induction of glutathione peroxidase activity were observed under hyperbaric O2 growth conditions without a corresponding change in the total glutathione and soluble thiol content. The difference in the expression of the enzyme, and its cognate substrate's intracellular concentration, under these conditions suggest that the gene encoding glutathione reductase is responsive to oxygen concentration, but that the genes encoding the glutathione synthesizing enzymes are not linked to an oxygen-sensitive promoter.

Amino Acid Sequence↗

PubMed2003

Biliary secretion of glutathione in estradiol 17beta-D-glucuronide-induced cholestasis.

Estradiol-17beta-D-glucuronide (E2-17G) induces an acute but reversible inhibition of bile flow after its intravenous administration to rats, due in part to the endocytic retrieval of the canalicular multidrug resistance-associated transporter protein 2 and the bile salt export pump, transporters that contribute to bile flow. Decreased bile salt-independent bile flow (BSIF) is also involved and persists during the phase of recovery from cholestasis. Because glutathione and HCO3- are major contributors to BSIF, we evaluated changes in their biliary excretion and the hepatic content of total glutathione during E2-17G-induced cholestasis. E2-17G acutely decreased bile flow and biliary excretion of total glutathione by about 80%; glutathione excretion was still inhibited at 80 min and 120 min, even though bile flow was partially and totally restored, respectively. Neither liver glutathione content nor the proportions of oxidized glutathione in bile and liver were affected by E2-17G at any time. HCO3- concentrations in bile were unchanged, so that secretion paralleled variations in bile flow. In the isolated perfused liver, addition of E2-17G decreased both bile flow and the biliary concentration of glutathione, whereas addition of its noncholestatic isomer estradiol-3-D-glucuronide (E2-3G) did not inhibit bile flow, but significantly reduced the concentration of glutathione in bile. The bile:liver concentration ratios of glutathione were significantly decreased in vivo by E2-17G and in the perfused liver by E2-17G and E2-3G. These data indicate that E2-17G cis-inhibits the canalicular transport of glutathione and thus contributes to the cholestatic effect by inhibiting BSIF.

Animals↗

PubMed2001

Glutathione in induced sputum of healthy individuals and patients with asthma.

BACKGROUND: Glutathione is central to the antioxidant defences of the lung. The aim of this study was to determine whether sputum induction can be used for the measurement of glutathione in the respiratory tract. METHODS: Saliva and induced sputum (3% NaCl, 20 minutes) samples were collected from 10 healthy individuals and 10 patients with stable asthma receiving treatment with inhaled corticosteroids. Samples were chilled on ice and dispersed by dilution with ice cold phosphate buffered saline and pipetting. Cell-free supernatants were obtained by centrifugation of samples and filtration of supernatants and analysed for total glutathione, glutathione disulfide, and albumin content. The cells were treated with dithiothreitol and cell numbers, cell viability, and differential cell patterns were determined. RESULTS: As judged by cell viability and percentage of non-squamous cells, adequate sputum samples were obtained from nine healthy and nine asthmatic subjects. The salivary total glutathione content was low (median concentration 1.2 microM (range 0.8-1.5) in healthy subjects and 0.9 microM (0.7-1. 2) in asthmatic subjects). The sputum total glutathione content of both healthy and asthmatic subjects was within the same range (3.9 (1.0-12.3) microM and 6.4 (1.3-19.2) microM, respectively; p=0.35). Surprisingly, and in marked contrast to results obtained with bronchoalveolar lavage, sputum levels of glutathione disulfide represented more than 50% of the total glutathione in both groups (50.9% (range 24.6-83.1) and 72.3% (range 36.5-97.4), respectively; p=0.2). CONCLUSIONS: The results of this study indicate that sputum induction can be used to measure the glutathione content of bronchial secretions. Sputum glutathione levels of stable asthmatic patients did not differ significantly from healthy controls.

Adolescent↗

PubMed1989

Determinants of glutathione efflux and biliary GSH/GSSG ratio in perfused rat liver.

Utilizing the isolated perfused rat liver, we examined several factors influencing efflux of glutathione [reduced glutathione (GSH) and glutathione disulfide (GSSG)] into perfusate and bile, including the effects of perfusate composition, oxygen delivery to the liver, and acivicin (AT-125), an inhibitor of gamma-glutamyl transferase activity. When livers were perfused with a recirculating Krebs-Ringer bicarbonate buffer only 7-26% of released glutathione was excreted into bile, mainly in its oxidized form (71-90% as GSSG). In contrast, when 20% bovine red blood cells or 20% fluorocarbon emulsion were utilized as perfusates, biliary glutathione accounted for a larger fraction of total hepatic efflux (16-41%), and only 39-65% was excreted as GSSG. To determine whether O2 delivery to the liver could explain some of these differences, biliary and sinusoidal efflux of glutathione were measured as O2 delivery was varied by 1) increasing the perfusion flow rate, 2) altering the concentration of fluorocarbon emulsion (5, 10, and 20%), and 3) changing the PO2 (95% O2-5% CO2 vs. 50% O2-5% CO2-45% N2). Under all experimental conditions, an increase in O2 delivery was accompanied by an increase in bile flow and in the concentration and rate of glutathione efflux into bile but no significant change in sinusoidal efflux of glutathione. Hepatic tissue GSH and GSSG levels were not affected by the various treatments. When gamma-glutamyl transferase activity was inhibited with AT-125, biliary glutathione increased to levels of approximately 50% of total hepatic efflux in fluorocarbon-perfused livers, and only 24-29% of the glutathione was excreted as GSSG.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed2001

Effects of citicoline on phospholipid and glutathione levels in transient cerebral ischemia.

BACKGROUND AND PURPOSE: Cytidine-5'-diphosphocholine (citicoline or CDP-choline) is an essential intermediate in the biosynthesis of phosphatidylcholine, an important component of the neural cell membrane. Citicoline provided significant neuroprotection after transient forebrain ischemia in gerbils. This study was undertaken to examine changes and effects of citicoline on phospholipids and glutathione synthesis after transient cerebral ischemia and reperfusion. METHODS: Ten-minute transient forebrain ischemia was induced by bilateral carotid artery occlusion in male Mongolian gerbils with reperfusion up to 6 days. Citicoline (500 mg/kg IP in saline) was given to gerbils just after the end of ischemia, at 3-hour reperfusion, and daily thereafter until 1 day before euthanasia. Hippocampal lipids were extracted and analyzed by thin-layer and gas chromatography. Glutathione was measured by using an enzymatic recycling assay. Glutathione reductase activity was determined by measuring NADPH oxidation. RESULTS: Significant decreases in phospholipids occurred at 1-day reperfusion. Citicoline significantly restored the phosphatidylcholine, sphingomyelin, and cardiolipin levels but did not affect phosphatidylinositol and phosphatidylserine at 1 day. The phospholipids returned to sham levels over days 2 to 6 and were unaffected by citicoline. Ceramide levels significantly increased by 3 and 6 days of reperfusion and were unaltered by citicoline. Ischemia resulted in significant decreases in glutathione and glutathione reductase activity over 3 days of reperfusion. Citicoline significantly increased total glutathione and glutathione reductase activity and decreased the glutathione oxidation ratio, an indicator of glutathione redox status. CONCLUSIONS: Our data indicated that the effects of citicoline on phospholipids occurred primarily during the first day of reperfusion, with effects on glutathione being important over the 3-day reperfusion period.

Animals↗

PubMed1999

Blood glutathione homeostasis as a determinant of resting and exercise-induced oxidative stress in young men.

Although the importance of glutathione in protection against oxidative stress is well recognized, the role of physiological levels of glutathione and other endogenous antioxidants in protecting against exercise-induced oxidative stress is less clear. We evaluated the role of glutathione and selected antioxidant enzymes as determinants of lipid peroxidation at rest and in response to exercise in men (n = 13-14) aged 20-30 years, who cycled for 40 min at 60% of their maximal oxygen consumption (VO2max). Levels of plasma thiobarbituric acid reactive substances (plasma TBARS) and blood oxidised glutathione (GSSG) increased by about 50% in response to exercise. Mean blood reduced glutathione (GSH) decreased by 13% with exercise. Of the measured red blood cell (RBC) antioxidant enzyme activities, only selenium-dependent glutathione peroxidase (Se-GPX) activity rose following exercise. In univariate regression analysis, plasma TBARS levels at rest predicted postexercise plasma TBARS and the exercise-induced change in total glutathione (TGSH). Blood GSSG levels at rest were strongly determinant of postexercise levels. Multiple regression analysis showed blood GSH to be a determinant of plasma TBARS at rest. The relative changes in TGSH were determinant of postexercise plasma TBARS. In summary, higher blood GSH and lower plasma TBARS at rest were associated with lower resting, and exercise-induced, lipid peroxidation. Subjects with a favourable blood glutathione redox status at rest maintained a more favourable redox status in response to exercise-induced oxidative stress. Changes in blood GSH and TGSH in response to exercise were closely associated with both resting and exercise-induced plasma lipid peroxidation. These results underscore the critical role of glutathione homeostasis in modulating exercise-induced oxidative stress and, conversely, the effect of oxidative stress at rest on exercise-induced changes in glutathione redox status.

Adult↗

PubMed1994

Responses of glutathione-related enzymes in isolated rat small intestine to Fe(2+)-EDTA-mediated oxidative stress.

The activities of glutathione-related enzymes in isolated rat small intestine were investigated under oxidative stress mediated by Fe(2+)-EDTA. The isoelectric points and approximate molecular weights of the enzymes investigated were first determined. The reduced and oxidized glutathione contents, and low molecular weight thiols in isolated rat small intestine were also studied under oxidative stress. Significant reducing activities of glutathione S-transferase and lactate dehydrogenase were observed accompanied by increases in oxidized glutathione content, whereas thioltransferase, glutathione reductase, glutathione peroxidase and thioredoxin reductase retained the same levels of activity as controls. First-order inactivation of purified rat small intestine glutathione S-transferase including class-alpha, mu and pi was observed and the isozyme class-pi was inactivated at several pH's under Fe(2+)-EDTA-mediated oxidative stress. Leakage of protein and both reduced and oxidized forms of glutathione was significantly increased during incubation with Fe(2+)-EDTA. In conclusion, enzymes which were not inactivated under Fe(2+)-EDTA-mediated oxidative stress may play an important role in cellular antioxidant defenses in the small intestine. Furthermore, enzymes such as glutathione S-transferase, mainly a class-pi isozyme, and lactate dehydrogenase which were inactivated may form part of the barrier against oxidative stress similar to reduced glutathione.

Animals↗

PubMedDate not supplied

In vitro effects of hyperoxia on alveolar type II pneumocytes: inhibition of glutathione synthesis increases hyperoxic cell injury.

An in vitro model of alveolar epithelial oxidant injury was developed based on exposure to hyperoxia of cultured guinea pig type II pneumocytes using a biphasic cell culture system in aerobiosis. The present study investigates the roles of intracellular antioxidant enzymes and of glutathione in providing protection against hyperoxia. A 2-day type II cell culture in normoxia was associated with a significant decrease in protein, catalase, and Cu-Zn SOD cell content, whereas ATP cell content, Mn-SOD, and glutathione peroxidase (GPx) activities did not change and glutathione cell content significantly increased. Exposure of type II cells to hyperoxia did not induce significant changes in cell content in protein, SOD, catalase, GPx, or glutathione cell content when compared to control cells (exposed to normoxia). With ATP cell content expressed as a cell injury index (CII), type II cell injury was found to increase with increasing O2 concentrations. Indeed, a 2-day 50% O2 and 95% O2 exposure resulted in a CII of -7.5 +/- 6.2% and 17.9 +/- 5.9%, respectively, LDH release by type II cells was not significantly increased after hypoxic exposure. Cell injury effects of hyperoxia did not correlate with the endogenous antioxidant enzyme activities (SOD, Mn-SOD, catalase). In marked contrast, there was a significant correlation between the CII and total glutathione content of type II cells (p < .01). This correlation was largely due to the close relationship between CII and reduced glutathione. Hyperoxic induced cell injury (as demonstrated by CII > 0) was clearly associated with significantly lower intracellular glutathione level when compared to experiments without hyperoxia induced cell injury (CII < 0). In addition, in the presence of buthionine sulfoximine (BSO), the ability of type II cells to synthetize new glutathione was severely impaired, whereas ATP cell content and cell antioxidant enzyme activities did not change. As a consequence, the reduction of intracellular glutathione significantly increased the susceptibility of cells to hyperoxia injury (p < .05). The results strongly support the hypothesis that the regulation of glutathione levels is an important mechanism in protecting hyperoxia-induced type II cell injury.

Aerobiosis↗

PubMed1999

Glutathione level and its relation to radiation therapy in patients with cancer of uterine cervix.

Glutathione functions as an important antioxidant in the destruction of hydrogen peroxide and lipid peroxides by providing substrate for the glutathione peroxidase and also promotes the ascorbic acid. Glutathione plays a vital role in detoxification of xenobiotics, carcinogens, free radicals and maintenance of immune functions. The study was aimed to determine plasma glutathione as well as erythrocyte glutathione and glutathione peroxidase in patients with invasive cervical carcinoma (n = 30) before initiation and after completion of radiotherapy and subsequently, at the time of first three monthly follow-up visit. The levels of plasma glutathione, erythrocyte glutathione and glutathione peroxidase activity were found to be lower in all cervical cancer patients as compared to age matched normal control women. The study indicates a change in antioxidant status in relation with the glutathione system among patients with invasive carcinoma of the uterine cervix. This study also demonstrates the effect of radiation therapy on this antioxidant system.

Adult↗

PubMed1982

Effect of selenium deficiency and vitamin E deficiency on glutathione metabolism in isolated rat hepatocytes.

Selenium deficiency and vitamin E deficiency both affect xenobiotic metabolism and toxicity. In addition, selenium deficiency causes changes in the activity of some glutathione-requiring enzymes. We have studied glutathione metabolism in isolated hepatocytes from selenium-deficient, vitamin E-deficient, and control rats. Cell viability, as measured by trypan blue exclusion, was comparable for all groups during the 5-h incubation. Freshly isolated hepatocytes had the same glutathione concentration regardless of diet group. During the incubation, however, the glutathione concentration in selenium-deficient hepatocytes rose to 1.4 times that in control hepatocytes. The selenium-deficient cells also released twice as much glutathione into the incubation medium as did the control cells. Total glutathione (intracellular plus extracellular) in the incubation flask increased from 47.7 +/- 8.9 to 152 +/- 16.5 nmol/10(6) selenium-deficient cells over 5 h compared with an increase from 46.7 +/- 7.1 to 92.0 +/- 17.4 nmol/10(6) control cells and from 47.7 +/- 11.7 to 79.5 +/- 24.9 nmol/10(6) vitamin E-deficient cells. This overall increase in glutathione concentration suggested that glutathione synthesis was accelerated by selenium deficiency. The activity of gamma-glutamylcysteine synthetase was twice as great in selenium-deficient liver supernatant (105,000 X g) as in vitamin E-deficient or control liver supernatant (105,000 X g). Hemoglobin-free perfused livers were used to determine the form of glutathione released and its route. Selenium-deficient livers released 4 times as much GSH into the caval perfusate as did control livers. Plasma glutathione concentration in selenium-deficient rats was found to be 2-fold that in control rats, suggesting that increased GSH synthesis and release is an in vivo phenomenon associated with selenium deficiency.

Animals↗

PubMed2001

The glutathione-related detoxification system is increased in human breast cancer in correlation with clinical and histopathological features.

PURPOSE: The glutathione detoxification pathway includes glutathione S-transferase (GST) and peroxidase (GPX) isoenzymes as well as glutathione reductase (GSSR). Though well established from cultured cancer cell lines, its involvement in resistance is still unclear in the tumours. This study aimed to describe the parameters that influence the glutathione contents and associated activities in breast cancer. METHODS: The components of the glutathione pathway were measured in the tumours from 41 women with primary breast cancer in comparison with those in the matched tumour-free samples. Appropriate statistical studies (regression analysis, Wilcoxon signed rank test) explored the influence of clinical and prognostic factors. RESULTS: Reduced and total glutathione contents were largely increased (P < 0.0001) and all related activities were significantly enhanced in the tumours. Interindividual variations were described, probably due to various parameters (age, menopause, axillary lymph node status, S and G2 + M cell fractions, ER, cathepsin-D and c-ErbB-2 expressions) that influence particular components of the glutathione pathway, especially the glutathione levels. CONCLUSIONS: The breast tumours improved their redox status and detoxification capacities depending on various parameters of significance for cell proliferation and aggressiveness, which supports the involvement of the glutathione pathway in malignant cell resistance to oxidative stress and apoptosis.

Adult↗

PubMed1992

Glutathione metabolic enzyme activities in diabetic platelets as a function of glycemic control.

Type 1 diabetic subjects categorized on the basis of the glycated haemoglobin content of their blood (low less than 7%; medium, greater than 7% and less than 11%; high, greater than 11%) were analyzed for total intraplatelet GSH as well as for the steady-state kinetic parameters (apparent KM and apparent Vmax) of some glutathione metabolic enzymes including glutathione reductase, glutathione peroxidase, gamma-glutamyltrans-peptidase and glutathione-S-transferase. This study indicates that intraplatelet GSH content of subjects with low glycated-haemoglobin is approximately 2-fold higher than those with medium glycated-haemoglobin. There was no further decrease in intraplatelet-GSH in subjects with high glycated-haemoglobin. The kinetic parameters of the platelet-enzymes studied (glutathione reductase, gamma-glutamyltranspeptidase and glutathione-S-transferase) were essentially independent of the glycation state of the subject. However, the apparent KM of glutathione peroxidase was approximately 4-fold higher in the subjects with high glycated-haemoglobin, in comparison to low subjects. This decrease in affinity could possibly result from the susceptibility of this enzyme to non-enzymatic glucosylation as purified samples of glutathione peroxidase incubated in vitro with glucose showed similar increases in apparent KM. These results are discussed in terms of the potential contribution of glutathione peroxidase impairment, to the hyperaggregability of the diabetic platelet.

Blood Platelets↗

PubMedDate not supplied

[The effect of phenobarbital, ionol and cAMP on the activity of glutathione metabolism enzymes in rodents].

The phenobarbital and ionol administration to rats and mice increases considerably the glutathione transferase, glutathione reductase and gamma-glutamyl transferase activities in the liver. The induction of these enzymes has been observed in a number of experiments in the heart and kidney but it was less pronounced. A correlation was established between the induction of glutathione transferase, glutathione reductase and gamma-glutamyl transferase, their changes in mice and rats, phenobarbital and ionol effects. The stimulatory effect of cAMP on glutathione transferase in the liver (and in a number of experiments in the heart) increased against a background of the both agents. The cAMP-dependent activation of glutathione peroxidase was retained in the heart but in some series experiments it disappeared in the liver and kidney. Mechanisms of the long-term (induction) and short-term (cAMP) elevation of the glutathione transferase and glutathione peroxidase activities functioned independently and often in concord. It is suggested that induction of glutathione metabolism enzymes may play an important role in biological effects of ionol.

Animals↗