Chronic depletion of glutathione (GSH) and minimal modification of LDL in vivo: its prevention by glutathione mono ester (GME) therapy

A decline in reduced glutathione (GSH) level is associated with aging and free radical mediated diseases. The objective of this study was to determine whether the chronic depletion of extra cellular GSH causes oxidative damage to the circulating macromolecules such as lipoproteins. Decreased concentrations of plasma glutathione, vitamin E and ascorbic acid were recorded in the rats treated with buthionine sulfoximine (BSO), a selective GSH inhibitor. In LDL isolated from BSO-treated animals, the concentration of malondialdehyde (MDA) and conjugated dienes were significantly increased (P<0.01), whereas the levels of vitamin E were decreased (P<0.01). The analysis of total and LDL cholesterol revealed significant changes between the control and experimental groups. Of interest, altered concentrations of lyso-phosphatidyl choline (Lyso-PC) and phosphatidyl choline (PC) were recorded from the BSO mediated minimally modified LDL. A negative correlation between LDL-BDC/MDA and its antioxidant capacity was noted. Upon in vitro oxidation with CuSO(4), the electrophoretic behavior of purified LDL-apoprotein-B on agarose gel showed an increased mobility in BSO-treated rats, indicative of in vivo modification of LDL to become susceptible for in vitro oxidation. The increased mobility of LDL (after in vitro oxidation) isolated from the BSO-treated animals correlates with a decrease in its amino groups, as determined by the trinitrobenzene sulfonic acid (TNBS) reactants. However, the mobility of LDL molecule was not altered due to BSO treatment in vivo. Interestingly, the minimal modification on LDL does not lead to any vascular damage in the dorsal aorta of the rats injected with BSO. The administration of glutathione monoester (GME), at a dose of 5 mmol/kg body weight, twice a day, for 30 days, to animals treated with l-buthionine-SR-sulfoximine (BSO, 4 mmol/kg body weight, twice a day, for 30 days) normalized the antioxidant status and prevented the minimal modifications on LDL. Thus, increasing the cellular GSH levels may trigger beneficial effects against oxidative stress.     

Cellular glutathione depletion by diethyl maleate or buthionine sulfoximine: no effect of glutathione depletion on the oxygen enhancement ratio

The hypoxic and euoxic radiation response for Chinese hamster lung and A549 human lung carcinoma cells was obtained under conditions where their nonprotein thiols, consisting primarily of glutathione (GSH), were depleted by different mechanisms. The GSH conjugating reagent diethylmaleate (DEM) was compared to DL-buthionine-S,R-sulfoximine (BSO), an inhibitor of glutathionine biosynthesis. Each reagent depleted cellular GSH to less than 5% of control values. A 2-hr exposure to 0.5 mM DEM or a 4- or 24-hr exposure to BSO at 10 or 1 mM, respectively, depleted cellular GSH to less than 5% of control values. Both agents sensitized cells irradiated under air or hypoxic conditions. When GSH levels are lowered to less than 5% by both agents, hypoxic DEM-treated cells exhibited slightly greater X-ray sensitization than hypoxic BSO-treated cells. The D0's for hypoxic survival curves were as follows: control, 4.87 Gy; DEM, 3.22 Gy; and BSO, 4.30 Gy for the V79 cells and 5.00 Gy versus 4.02 Gy for BSO-treated A549 cells. The D0's for aerobic V79 cells were 1.70 Gy versus 1.13 Gy, DEM, and 1.43 Gy for BSO-treated cells. The D0's for the aerobic A549 were 1.70 and 1.20 for BSO-treated cells. The aerobic and anoxic sensitization of the cells results in the OER's of 2.8 and 3.0 for the DEM- and BSO-treated cells compared to 2.9 for the V79 control A549. BSO-treated cells showed an OER of 3.3 versus 3 for the control. Our results suggest that GSH depletion by either BSO or DEM sensitizes aerobic cells to radiation but does not appreciably alter the OER.     

Inhibition of elevated hepatic glutathione abolishes copper deficiency cholesterolemia.

Dietary copper deficiency causes hypercholesterolemia and increased hepatic 3-hydroxy-3-methyl-glutaryl coenzyme A (MHG-CoA) reductase activity and increased hepatic glutathione (GSH) in rats. We hypothesized that inhibition of GSH production by L-buthionine sulfoximine (BSO), a specific GSH synthesis inhibitor, would abolish the cholesterolemia and increased HMG-CoA reductase activity of copper deficiency. In two experiments, two groups of 20 weanling male rats were fed diets providing 0.4 and 5.8 micrograms Cu/g, copper-deficient (Cu-D) and copper-adequate (Cu-A), respectively. At 35 days plasma cholesterol was significantly elevated by 30 to 43% in Cu-D and 10 animals in each of the Cu-D and Cu-A groups were randomly assigned to receive 10 mM BSO solution in place of drinking water and continued on the same diets for another 2 wk. At necropsy Cu-D animals had a significant 52 to 58% increase in plasma cholesterol. BSO administration abolished the cholesterolemia in Cu-D rats, but had no influence on plasma cholesterol of Cu-A rats. Hepatic GSH was increased 39 to 82% in Cu-D rats and BSO abolished this increase. BSO was without effect on cardiac hypertrophy, plasma and liver copper, and hematocrit indices of copper status. Liver microsome HMG-CoA reductase activity was significantly increased 85 to 288% in Cu-D rats and BSO administration abolished this increase in activity in Cu-D rats. The results suggest that copper deficiency cholesterolemia and elevated HMG-CoA reductase activity are a consequence of elevated hepatic GSH, and provide evidence for GSH regulation of cholesterol metabolism in intact animals.     

Modulation of rat erythrocyte antioxidant defense system by buthionine sulfoximine and its reversal by glutathione monoester therapy

The protective effects of glutathione monoester (GME) on buthionine sulfoximine (BSO)-induced glutathione (GSH) depletion and its sequel were evaluated in rat erythrocyte/erythrocyte membrane. Animals were divided into three groups (n=6 in each): control, BSO and BSO+GME group. Administration of BSO, at a concentration of 4 mmol/kg bw, to the albino rats resulted in depletion of blood GSH level to about 59%. GSH was elevated several folds in the GME group as compared to the control (P<0.05) and BSO (P<0.001) groups. Decreased concentration of vitamin E was found in the erythrocyte membrane isolated from BSO-administered animals. Antioxidant enzymes, catalase (CAT), superoxide dismutase (SOD) and glutathione peroxidase (GPX) were also found to be altered due to BSO-induced GSH depletion in blood erythrocytes. The SOD and CAT activities in BSO group were significantly lower (P<0.001) than the other groups. Lipid peroxidation index and malondialdehyde (MDA) levels in erythrocytes and their membranes were increased to about 45% and 40%, respectively. The activities of Ca2+ ATPase, Mg2+ ATPase and Na+K+ ATPase were lower than those of control group (P<0.05), whereas the activities of these enzymes were found to be restored to normal followed by GME therapy (P<0.05). Cholesterol, phospholipid and C/P ratio and some of the phospholipid classes like phosphatidylcholine (PC), lysophosphatidylcholine (LPC) and sphingomyelin were significantly (P<0.05) altered in the erythrocyte membranes of BSO-administered rats compared with those of control group. These parameters were restored to control group levels in GME-treated group. Oxidative stress may play a major role in the BSO-mediated gamma glutamyl cysteine synthetase (gamma-GCS) inhibition and hence the depletion of GSH. In conclusion, our findings have shown that antioxidant status decreased and lipid peroxidation increased in BSO-treated rats. GME potentiates the RBC and blood antioxidant defense mechanisms and decreases lipid peroxidation.     

Aging reduces responsiveness to BSO- and heat stress-induced perturbations of glutathione and antioxidant enzymes

Aging alters cellular responses to both heat and oxidative stress. Thiol-mediated metabolism of reactive oxygen species (ROS) is believed to be important in aging. To begin to determine the role of thiols in aging and heat stress, we depleted liver glutathione (GSH) by administering l-buthionine sulfoximine (BSO) in young (6 mo) and old (24 mo) Fisher 344 rats before heat stress. Animals were given BSO (4 mmol/kg ip) or saline (1 ml ip) 2 h before heat stress and subsequently heated to a core temperature of 41 degrees C over a 90-min period. Liver tissue was collected before and 0, 30, and 60 min after heat stress. BSO inhibited glutamate cysteine ligase (GCL, the rate-limiting enzyme in GSH synthesis) catalytic activity and resulted in a decline in liver GSH and GSSG that was more pronounced in young compared with old animals. Catalase activity did not change between groups until 60 min after heat stress in young BSO-treated rats. Young animals experienced a substantial and persistent reduction in Cu,Zn-SOD activity with BSO treatment. Mn-SOD activity increased with BSO but declined after heat stress. The differences in thiol depletion observed between young and old animals with BSO treatment may be indicative of age-related differences in GSH compartmentalization that could have an impact on maintenance of redox homeostasis and antioxidant balance immediately after a physiologically relevant stress. The significant changes in antioxidant enzyme activity after GSH depletion suggest that thiol status can influence the regulation of other antioxidant enzymes.     

Plasma glutathione turnover in the rat: effect of fasting and buthionine sulfoximine

Hepatic glutathione (GSH) plays an important role in the detoxification of reactive molecular intermediates. Because of evidence that the intrahepatic turnover of glutathione in the rat may be largely accounted for by efflux from hepatocytes into the general circulation, the quantitation of plasma GSH turnover in vivo could provide a noninvasive index of hepatic glutathione metabolism. We developed a method to estimate plasma glutathione turnover and clearance in the intact, anesthetized rat using a 30-min unprimed, continuous infusion of 35S-labelled GSH. A steady state of free plasma glutathione specific radioactivity was achieved within 10 min, as determined by high-pressure liquid chromatography with fluorometric detection after precolumn derivatization of the plasma samples with monobromobimane. The method was tested after two treatments known to alter hepatic GSH metabolism: 90 min after intraperitoneal injection of 4 mmol/kg buthionine sulfoximine (BSO), an inhibitor of glutathione synthesis, and after a 48-h fast. Liver glutathione concentration (mean +/- SEM) was 5.00 +/- 0.53 mumol/g wet weight in control rats. It decreased to 3.10 +/- 0.35 mumol/g wet weight after BSO injection and to 3.36 +/- 0.14 mumol/g wet weight after fasting (both p less than 0.05). Plasma glutathione turnover was 63.0 +/- 7.46 nmol.min-1.100 g-1 body weight in control rats, 35.0 +/- 2.92 nmol.min-1.g-1 body weight in BSO-treated rats, and 41.7 +/- 2.28 nmol.min-1.g-1 body weight after fasting (both p less than 0.05), thus reflecting the hepatic alterations. This approach might prove useful in the noninvasive assessment of liver glutathione status.     

Improved development of microspore-derived embryo cultures of Brassica napus cv Topaz following changes in glutathione metabolism

Glutathione has been shown to play an important role during embryo development in both plant and animal systems. The effects of altered glutathione metabolism during microspore-derived embryos (MDEs) of Brassica napus were investigated following exogenous application of reduced glutathione (GSH), its oxidized form (GSSG) and buthionine sulfoximine (BSO), an inhibitor of glutathione de novo synthesis. Applications of BSO which lowered the cellular glutathione redox status, i.e. GSH/(GSH + GSSG), enhanced significantly the quality of the embryos and their ability to convert into viable plants. Histological analyses revealed that inclusions of BSO in the culture medium altered the pattern of storage product accumulation in the embryos and improved the architecture of the shoot apical meristems (SAMs). Compared with their control counterparts which showed severe signs of SAM deterioration, such as the formation of intercellular spaces and differentiation of the meristematic cells, BSO-treated embryos had well-organized SAMs. The improved SAM organization observed in the presence of BSO also correlated with the proper localization pattern of WUSCHEL , a SAM molecular marker gene which was miss-expressed in control embryos. The beneficial effects of BSO on embryo development and conversion were ascribed to the increasing levels of ABA. The concentration of this growth regulator in BSO-treated embryos was always higher than that of control embryos during the second half of the maturation period. Furthermore, many structural alterations induced by BSO could be reproduced in embryos cultured in the presence of ABA. Taken together, these results suggest that a lowering of the glutathione redox status during embryo development may represent a metabolic switch needed for increasing the endogenous levels of ABA, which is required for successful completion of the developmental program.     

Protection from hyperbaric oxidant stress by administration of buthionine sulfoximine.

To explore the role of glutathione in protecting rats from hyperbaric hyperoxia, we administered buthionine sulfoximine (BSO) to block gamma-glutamyl cysteine synthase activity and decrease tissue glutathione synthesis. We then exposed these animals and their vehicle-treated matched controls to 100% oxygen at 4 ATA or room air at 1 ATA. After BSO treatment, glutathione concentrations in air-exposed controls decreased 62% in lung, 76% in liver, 28% in brain, and 62% in plasma. Paradoxically, BSO-treated rats were protected from hyperbaric hyperoxia. The BSO-treated animals seized significantly later and had a markedly prolonged time of survival compared with the vehicle-treated controls. We conclude that BSO treatment protects rats from hyperbaric hyperoxia, despite its effects of lowering plasma and tissue glutathione concentrations. This protection may be related to a direct effect of the compound in decreasing free radical-mediated tissue injury, increasing tissue antioxidant defenses, or increasing seizure threshold.     

Inhibition of glutathione synthesis reduces chilling tolerance in maize

 The role of glutathione (GSH) in protecting plants from chilling injury was analyzed in seedlings of a chilling-tolerant maize (Zea mays L.) genotype using buthionine sulfoximine (BSO), a specific inhibitor of γ-glutamylcysteine (γEC) synthetase, the first enzyme of GSH synthesis. At 25 °C, 1 mM BSO significantly increased cysteine and reduced GSH content and GSH reductase (GR: EC 1.6.4.2) activity, but interestingly affected neither fresh weight nor dry weight nor relative injury. Application of BSO up to 1 mM during chilling at 5 °C reduced the fresh and dry weights of shoots and roots and increased relative injury from 10 to almost 40%. Buthionine sulfoximine also induced a decrease in GR activity of 90 and 40% in roots and shoots, respectively. Addition of GSH or γEC together with BSO to the nutrient solution protected the seedlings from the BSO effect by increasing the levels of GSH and GR activity in roots and shoots. During chilling, the level of abscisic acid increased both in controls and BSO-treated seedlings and decreased after chilling in roots and shoots of the controls and in the roots of BSO-treated seedlings, but increased in their shoots. Taken together, our results show that BSO did not reduce chilling tolerance of the maize genotype analyzed by inhibiting abscisic acid accumulation but by establishing a low level of GSH, which also induced a decrease in GR activity. Received: 9 November 1999 / Accepted: 17 February 2000     

Hepatic glutathione and nitric oxide are critical for hepatic insulin-sensitizing substance action

We tested the hypothesis that hepatic nitric oxide (NO) and glutathione (GSH) are involved in the synthesis of a putative hormone referred to as hepatic insulin-sensitizing substance HISS. Insulin action was assessed in Wistar rats using the rapid insulin sensitivity test (RIST). Blockade of hepatic NO synthesis with N(G)-nitro-l-arginine methyl ester (l-NAME, 1.0 mg/kg intraportal) decreased insulin sensitivity by 45.1 +/- 2.1% compared with control (from 287.3 +/- 18.1 to 155.3 +/- 10.1 mg glucose/kg, P < 0.05). Insulin sensitivity was restored to 321.7 +/- 44.7 mg glucose/kg after administration of an NO donor, intraportal SIN-1 (5 mg/kg), which promotes GSH nitrosation, but not after intraportal sodium nitroprusside (20 nmol x kg(-1) x min(-1)), which does not nitrosate GSH. We depleted hepatic GSH using the GSH synthesis inhibitor l-buthionine-[S,R]-sulfoximine (BSO, 2 mmol/kg body wt ip for 20 days), which reduced insulin sensitivity by 39.1%. Insulin sensitivity after l-NAME was not significantly different between BSO- and sham-treated animals. SIN-1 did not reverse the insulin resistance induced by l-NAME in the BSO-treated group. These results support our hypothesis that NO and GSH are essential for insulin action.     

Buthionine sulfoximine causes endothelium dependent hyper-relaxation and hypoadiponectinemia

A close relationship between oxidative stress, endothelial dysfunction, and hypoadiponectinemia has been observed. The present study was performed to investigate how glutathione depletion via buthionine sulfoximine (BSO) administration affects endothelial function and adiponectin levels in rats. Acetylcholine (Ach)-induced vasodilation was significantly enhanced in BSO-treated rats, compared with control rats. This was completely abolished by L-NAME, and Ach-induced vasodilation was not observed in the aorta without endothelium. These results suggest that Ach-induced hyper-relaxation of the aorta in BSO-treated rats is completely dependent on the presence of endothelium and mediated by changes in eNOS activity. Catalase significantly inhibited this relaxation to Ach and no effect of catalase on sodium nitroprusside-induced relaxation of the aorta without endothelium was observed in BSO-treated rats. Thus, hyper-relaxation of the aorta in BSO-treated rats is likely caused by H₂O₂ in addition to NO produced by the endothelium via an eNOS-dependent mechanism. Hypoadiponectinemia and decreased levels of adiponectin mRNA in adipose tissue were observed in BSO-treated rats. Protein expression of eNOS and SODs (SOD-1 and SOD-2) in the aorta was increased and plasma NOx levels were decreased in BSO-treated rats. Our results suggest that oxidative stress induced by BSO causes eNOS uncoupling and hyper-relaxation by producing H₂O₂, and that BSO-induced oxidative stress causes hypoadiponectinemia, probably by increasing H₂O₂ production in adipose tissue.     

Oral glutathione increases tissue glutathione in vivo

Mice were given an oral dose of glutathione (GSH) (100 mg/kg) and concentrations of GSH were measured at 30, 45 and 60 min in blood plasma and after 1 h in liver, kidney, heart, lung, brain, small intestine and skin. In control mice, GSH concentrations in plasma increased from 30 microM to 75 microM within 30 min of oral GSH administration, consistent with a rapid flux of GSH from the intestinal lumen to plasma. Under these GSH-sufficient conditions, no increases over control values were obtained in GSH concentrations in most tissues except lung over the same time course. Mice pretreated for 5 days with the GSH synthesis inhibitor, L-buthionine-S,R-sulfoximine (BSO, 80 mumol/day) had substantially decreased tissue concentrations of GSH. Oral administration of GSH to these GSH-deficient animals gave statistically significant increases in GSH concentrations in kidney, heart, lung, brain, small intestine and skin but not in the liver. Administration of the equivalent amount of the constituent amino acids, glutamate, cysteine, and glycine, resulted in little change in GSH concentrations in all tissues in GSH-deficient animals. Thus, the results show that oral GSH can increase GSH concentrations in several tissues following GSH depletion, such as can occur in toxicological and pathological conditions in which GSH homeostasis is compromised.     

Metabolic cooperation of ascorbic acid and glutathione in normal and vitamin C-deficient ODS rats.

Although the coordination of various antioxidants is important for the protection of organisms from oxidative stress, dynamic aspects of the interaction of endogenous antioxidants in vivo remain to be elucidated. We studied the metabolic coordination of two naturally occurring water-soluble antioxidants, ascorbic acid (AA) and reduced glutathione (GSH), in liver, kidney and plasma of control and scurvy-prone osteogenic disorder Shionogi (ODS) rats that hereditarily lack the ability to synthesize AA. When supplemented with AA, its levels in liver and kidney of ODS rats increased to similar levels of those in control rats. Hepato-renal levels of glutathione were similar with the two animal groups except for the slight increase in its hepatic levels in AA-supplemented ODS rats. Administration of L-buthionine sulfoximine (BSO), a specific inhibitor of GSH synthesis, rapidly decreased the hepato-renal levels of glutathione in a biphasic manner, a rapid phase followed by a slower phase. Kinetic analysis revealed that glutathione turnover was enhanced significantly in liver mitochondria and renal cytosol of ODS rats. Administration of BSO significantly increased AA levels in the liver and kidney of control rats but decreased them in AA-supplemented ODS rats. Kinetic analysis revealed that AA is synthesized by control rat liver by some BSO-enhanced mechanism and the de novo synthesized AA is transferred to the kidney. Such a coordination of the metabolism of GSH and AA in liver and kidney is suppressed in AA-deficient ODS rats. These and other results suggest that the metabolism of AA and GSH forms a compensatory network by which oxidative stress can be decreased.     

Effect of selenium deficiency on the disposition of plasma glutathione

Selenium deficiency causes increased hepatic synthesis and release of GSH into the blood. The purpose of this study was to examine the effect of selenium deficiency on the disposition of plasma glutathione. Plasma glutathione concentration was 40 +/- 3.4 nmol GSH equivalents/ml in selenium-deficient rats and 17 +/- 5.4 nmol GSH equivalents/ml in control rats. The half-life and systemic clearance of plasma glutathione were found to be the same in selenium-deficient and control rats (t1/2 = 3.4 +/- 0.7 min). Because selenium-deficient plasma glutathione concentration was twice that of control, the determination that selenium deficiency did not affect glutathione plasma systemic clearance indicated that the flux of glutathione through the plasma was doubled by selenium deficiency. It has been proposed that the kidney is responsible for the removal of a major fraction of plasma glutathione. In these studies, renal clearance accounted for 24% of plasma systemic glutathione clearance in controls and 44% in selenium-deficient rats. This indicates that a significant amount of glutathione is metabolized at extrarenal sites, especially in control animals. More than half of the increased plasma glutathione produced in selenium deficiency was removed by the kidney. Thus, selenium deficiency results in a doubling of cysteine transport in the form of glutathione from the liver to the periphery as well as a doubling of plasma glutathione concentration.     

Association of glutathione with flowering in Arabidopsis thaliana

In order to study the relationship between GSH and flowering, wild-type and late-flowering mutant, fca-1, of Arabidopsis thaliana were treated with L-buthionine sulfoximine (BSO), a specific inhibitor of GSH biosynthesis, under long-day conditions. BSO treatment of the fca-1 mutant starting at 17 d after imbibition promoted flowering. However, when the treatment was started at 12 d after imbibition, BSO treatment at 10(-4) M resulted in an inhibition of flowering. This inhibitory effect of BSO on flowering was abolished by GSH treatment at 10(-4) M, although GSH treatment at an increased concentration of 10(-3) M clearly delayed flowering. In contrast, BSO treatment of wild-type plants starting at 12 d after imbibition promoted flowering, whose effect was abolished by GSH application. In the fca-1 mutant, whose endogenous GSH levels were high, chilling treatment lowered the GSH levels and promoted flowering, as was the case in the BSO treatment. An A. thaliana mutant, cad2-1, which has a defect in GSH biosynthesis also exhibited late flowering. The late-flowering phenotype of this mutant tended to be strengthened by BSO and abolished by GSH treatment. These results suggest that flowering is associated with the rate of GSH biosynthesis and/or the levels of GSH in A. thaliana.     

Free radical scavenger depletion in post-ischemic reperfusion brain damage

In the present study the influence of pretreatment with various GSH depletors such as buthionine sulfoximine (BSO) and diethylmaleate (DEM) was investigated in rats following cerebral postischemic reperfusion. Moreover, the effect of diethyldithiocarbamic acid (DDC), inhibitor of endogenous Cu,Zn-SOD, was evaluated. A significant depletion (40% of control value) of GSH levels was observed 24 h after DEM administration; after 48 h the value reached control levels. BSO showed maximal GSH depletion (59%) 24 h after administration and it was constant for almost 48 h. DDC administration caused a marked decrease (60%) of Cu,Zn-SOD activity 4 h after the injection and induced a marked decrease in percentage of survival with respect to control (untreated, ischemic) rats, when administered 4 h before ischemia. BSO and DEM prolonged the survival time of animals when administered 24 h before ischemia. This last paradoxical effect is unclear at present, but it might be due to an influence on glutamate cascade.     

Rat kidney function related to tissue glutathione levels. Effects of different glutathione depletors

1. Rat renal function was evaluated during acute depletion of glutathione (GSH) produced by different doses of diethyl-maleate (DEM) or buthionine-sulfoximine (BSO). 2. Similar alterations in renal function were observed when similar GSH levels were obtained independently of the GSH depletor employed. 3. These results confirm the relationship between GSH levels and renal function.     

Physical exercise intensity can be related to plasma glutathione levels

The aim of the present study was to examine the effect of different kinds of physical exercise on plasma glutathione levels. Male Wistar rats were randomly divided into four groups: In walking group (W; n=6), rats were trained to walk 0.8 m/min for 45 min; slow running group (SR; n=6) were trained to run 4 m/min for 45 min; fast running group (FR; n=6) ran 8m/min for 60 min and control rats (C; n=6) remained in their home cages. All animals were sacrificed after exercise and the levels of reduced glutathione (GSH) in plasma samples determined by high performance liquid chromatography (HPLC) with a fluorescent detector. Compared to controls, exercise did not change GSH plasma levels of the W group. A tendency to decrease blood GSH was observed in plasma samples of the SR group and in the FR group, physical exercise resulted in a dramatic decrease in GSH plasma levels. These data suggest that during light physical exercise there is a low production of reactive oxygen species (ROS) with a low request for antioxidant defence such as oxidation of GSH. The dramatic decrease observed in GSH levels in FR rats would indicate the presence of oxidative stress able to modify blood antioxidant profiles. Our results suggest that GSH plays a central antioxidant role in blood during intensive physical exercise and that its modifications are closely related to exercise intensity.     

Elevation of renal glutathione enhances ischemic injury.

In a previous study, we tested the hypothesis that an elevated level of renal glutathione (GSH) would protect the kidney from ischemic injury. However, prior elevation of GSH with GSH monoethylester enhanced then injury induced by 35 min of ischemia and blood reflow [Scaduto RC Jr, Gattone VH, Grotyohann LW, et al; Effect of an altered glutathione content on renal ischemic injury. Am J Physiol 1988;255:F911-F921]. Additionally, GSH monoethylester produced morphologic alterations in the absence of ischemia. Thus the greater ischemic injury observed after GSH ester pretreatment could have been due to a synergistic effect between the events caused by ischemia and the pretreatment. The present study was conducted to evaluate the utility of elevating renal GSH levels by administration of GSH. Administration of GSH (1 mmol/kg body weight) caused a 3-fold elevation of renal GSH levels and a 6-fold elevation of renal cysteine levels after 60 min without causing changes in renal morphology or GFR. After 35 min of renal artery occlusion and 90 min of blood reflow, animals pretreated with GSH had a much greater decline in GFR than untreated control animals. This enhancement of renal ischemic injury in GSH-treated animals was similar to that observed following administration of GSH monoethylester. We conclude that administration of GSH is the method of choice for elevation of renal GSH and that elevation of renal GSH leads to an enhanced ischemia-induced injury which is independent of the method employed to elevate renal GSH.     

Physical exercise intensity can be related to plasma glutathione levels

The aim of the present study was to examine the effect of different kinds of physical exercise on plasma glutathione levels. Male Wistar rats were randomly divided into four groups: In walking group (W; n=6), rats were trained to walk 0.8 m/min for 45 min; slow running group (SR; n=6) were trained to run 4 m/min for 45 min; fast running group (FR; n=6) ran 8m/min for 60 min and control rats (C; n=6) remained in their home cages. All animals were sacrificed after exercise and the levels of reduced glutathione (GSH) in plasma samples determined by high performance liquid chromatography (HPLC) with a fluorescent detector. Compared to controls, exercise did not change GSH plasma levels of the W group. A tendency to decrease blood GSH was observed in plasma samples of the SR group and in the FR group, physical exercise resulted in a dramatic decrease in GSH plasma levels. These data suggest that during light physical exercise there is a low production of reactive oxygen species (ROS) with a low request for antioxidant defence such as oxidation of GSH. The dramatic decrease observed in GSH levels in FR rats would indicate the presence of oxidative stress able to modify blood antioxidant profiles. Our results suggest that GSH plays a central antioxidant role in blood during intensive physical exercise and that its modifications are closely related to exercise intensity.