Effects of angiotensin II type 1 receptor blockade on the oxidative stress in spontaneously hypertensive rat tissues

The aim of this work was to investigate the production of oxidative damage in homogenized kidney, liver and brain of spontaneously hypertensive rats (SHR), as well as the involvement of angiotensin (Ang) II in this process. Groups of 12-week-old SHR and Wistar Kyoto rats (WKY) were given 10 mg/kg/day losartan in the drinking water during 14 days. Other groups of WKY and SHR without treatment were used as controls. The production of thiobarbituric acid reactive substances (TBARS), reduced glutathione (GSH) and the activity of the antioxidant enzymes catalase (CAT), superoxide dismutase (SOD) and glutathione peroxidase (Gpx) were determined. No significant difference in TBARS was observed between untreated SHR or WKY rats; GSH content was lower in the liver but higher in the brain of SHR compared to WKY rats. In tissues from the SHR group, SOD and Gpx activities were reduced, whereas CAT activity was slightly increased in kidney. TBARS levels did not change in WKY rats after losartan administration, but were reduced in SHR liver and brain. Losartan treatment decreased GSH content in WKY kidney, but increased GSH in SHR liver. The activity of the antioxidant enzymes was not modified by losartan in WKY rats; however, their activities increased in tissues from treated SHR. The lower activity of antioxidant enzymes in tissues from hypertensive rats compared to those detected in normotensive controls, indicates oxidative stress production. Ang II seems to play no role in this process in normotensive animals, although AT1 receptor blockade in SHR enhances the enzymatic activity indicating that Ang II is implicated in oxidative stress generation in the hypertensive animals.     

Antioxidant status,lipid peroxidation,mixed function oxidase and UDP-glucuronyl transferase activities in livers from control and DOCA salt-hypertensive male Sprague Dawley rats

The effects of DOCA-salt hypertensive treatment on hepatic glutathione-dependent defense system, antioxidant enzymes, lipid peroxidation, mixed function oxidase and UDP-glucuronyl transferase activities were investigated in male Sprague Dawley rats.Compared with controls, DOCA-salt hypertensive rats had lower body weights (linked to liver hypertrophy). Mixed function oxidase and p-nitrophenol-UGT activities were not affected by the treatment but a significant lower rate of the glucuronoconjugation rate of bilirubin (p < 0.001) was observed in DOCA-salt hypertensive rats. While cytosolic glutathione contents and glutathione reductase activity were not affected, glutathione peroxidase (p < 0.001), glutathione transferase (p < 0.001) and catalase (p < 0.01) activities were decreased and associated with higher malondialdehyde contents (p < 0.001) in treated rats. The imbalance in liver antioxidant status (increasing generation of cellular radical species), associated with increases in lipid peroxidation, suggests that oxidative stress might be directly related to arterial hypertension in DOCA-salt treated male Sprague Dawley rats.     

Antioxidant activity of propionyl-L-carnitine in liver and heart of spontaneously hypertensive rats

Oxidative stress plays an important role in arterial hypertension and propionyl-L-carnitine (PLC) has been found to protect cells from toxic reactive oxygen species. In this work, we have evaluated the antioxidant capacity of chronic PLC treatment in spontaneously hypertensive rats (SHR) by measuring the activity of antioxidant enzymes and the lipid peroxidation in liver and cardiac tissues. The activity of glutathione peroxidase was decreased in liver and cardiac tissues of SHR when compared with their normotensive controls, Wistar- Kyoto (WKY) rats, this alteration being prevented by PLC treatment. Glutathione reductase activity was increased in hypertensive rats and no effect was observed after the treatment. No significant changes in superoxide dismutase activity were observed among all experimental groups. Liver of hypertensive rats showed higher catalase activity than that of normotensive rats, and PLC enhanced this activity in both rat strains. Thiobarbituric acid reactive substances, determined as a measure of lipid peroxidation, were increased in SHR compared with WKY rats, and PLC treatment decreased these values not only in hypertensive rats but also in normotensive ones. The content of carnitine in serum, liver and heart was higher in PLC-treated rats, but PLC did not prevent the hypertension development in young SHR. In addition, triglyceride levels, which were lower in SHR than WKY rats, were reduced by chronic PLC treatment in both rat strains. These results demonstrate: i) the hypotriglyceridemic effect of PLC and ii) the antioxidant capacity of PLC in SHR and its beneficial use protecting tissues from hypertension-accompanying oxidative damage.     

Effects of quercetin on antioxidant defense in streptozotocin-induced diabetic rats.

In light of evidence that some complications of diabetes mellitus may be caused or exacerbated by oxidative damage, we investigated the effects of subacute treatment with the antioxidant quercetin on tissue antioxidant defense systems in streptozotocin-induced diabetic Sprague-Dawley rats (30 days after streptozotocin induction). Quercetin, 2-(3,4-dihydroxyphenyl)-3,5,7-trihydroxy-4H-1-benzopyran-4-one, was administered at a dose of 10mg/kg/day, ip for 14 days, after which liver, kidney, brain, and heart were assayed for degree of lipid peroxidation, reduced and oxidized glutathione content, and activities of the free-radical detoxifying enzymes catalase, superoxide dismutase, glutathione peroxidase, and glutathione reductase. Treatment of normal rats with quercetin increased serum AST and increased hepatic concentration of oxidized glutathione. All tissues from diabetic animals exhibited disturbances in antioxidant defense when compared with normal controls. Quercetin treatment of diabetic rats reversed only the diabetic effects on brain oxidized glutathione concentration and on hepatic glutathione peroxidase activity. By contrast, a 20% increase in hepatic lipid peroxidation, a 40% decline in hepatic glutathione concentration, an increase in renal (23%) and cardiac (40%) glutathione peroxidase activities, and a 65% increase in cardiac catalase activity reflect intensified diabetic effects after treatment with quercetin. These results call into question the ability of therapy with the antioxidant quercetin to reverse diabetic oxidative stress in an overall sense.     

Characterization of Oxidative Stress in Various Tissues of Diabetic and Galactose-fed Rats

Rats fed a galactose-rich diet have been used for several years as a model for diabetes to study, particularly in the eye, the effects of excess blood hexoses. This study sought to determine the utility of galactosemia as a model for oxidative stress in extraocular tissues by examining biomarkers of oxidative stress in galactose-fed rats and experimentally-induced diabetic rats. Sprague-Dawley rats were divided into four groups: experimental control; streptozotocin-induced diabetic; insulin-treated diabetic; and galactose-fed. The rats were maintained on these regimens for 30 days, at which point the activities of catalase, glutathione peroxidase, glutathione reductase, and superoxide dismutase, as well as levels of lipid peroxidation and reduced and oxidized glutathione were determined in heart, liver, and kidney. This study indicates that while there are some similarities between galactosemic and diabetic rats in these measured indices of oxidative stress (hepatic catalase activity levels and hepatic and renal levels of oxidized glutathione in both diabetic and galactosemic rats were significantly decreased when compared to normal), overall the galactosemic rat model is not closely parallel to the diabetic rat model in extra-ocular tissues. In addition, several effects of diabetes (increased hepatic glutathione peroxidase activity, increased superoxide dismutase activity in kidney and heart, decreased renal and increased cardiac catalase activity) were not mimicked in galactosemic rats, and glutathione concentration in both liver and heart was affected in opposite ways in diabetic rats and galactose- fed rats. Insulin treatment reversed/prevented the activity changes in renal and cardiac superoxide dismutase, renal and cardiac catalase, and hepatic glutathione peroxidase as well as the hepatic changes in lipid peroxidation and reduced and oxidized glutathione, and the increase in cardiac glutathione. Thus, prudence should be exercised in the use of experimentally galactosemic rats as a model for diabetes until the correspondence of the models has been more fully characterized.     

Antioxidant capacity responsible for a hypocholesterolemia is independent of dietary cholesterol in adult rats fed rice protein

Dietary cholesterol and aging are major risk factors to accelerate oxidation process for developing hypercholesterolemia. The major aim of this study is to elucidate the effects of rice protein on cholesterol level and oxidative stress in adult rats fed with and without cholesterol. After 2 weeks of feeding, hepatic and plasma contents of cholesterol, reduced glutathione (GSH), oxidized glutathione (GSSG), malondialdehyde (MDA) and protein carbonyl (PCO) were measured. In liver, total antioxidative capacity (T-AOC), activities of antioxidant enzymes (total superoxide dismutase, T-SOD; catalase, CAT), glutathione metabolizing enzyme activities and gene expression levels (γ-glutamylcysteine synthetase, γ-GCS; glutathione reductase, GR; glutathione peroxidase, GPx) were determined. Under cholesterol-free/enriched dietary condition, T-AOC, activities of T-SOD and CAT, glutathione metabolism related enzymes' activities and mRNA levels (γ-GCS, GR and GPx) were effectively stimulated by rice proteins as compared to caseins. Compared with caseins, rice proteins significantly increased hepatic and plasma GSH contents, whereas hepatic and plasma accumulations of MDA, PCO and GSSG were significantly reduced by rice protein-feedings. As a result, the marked reductions of cholesterol in the plasma and in the liver were observed in adult rats fed rice proteins with and without cholesterol. The present study demonstrates that the hypocholesterolemic effect of rice protein is attributable to inducing antioxidative response and depressing oxidative damage in adult rats fed cholesterol-free/enriched diets. Results suggest that the antioxidant capability involved in the hypocholesterolemic action exerted by rice protein is independent of dietary cholesterol during adult period.     

Strain difference (WKY,SPRD) in the hepatic antioxidant status in rat and effect of hypertension (SHR,DOCA). Ex vivo and in vitro data

We assessed the hepatic antioxidant status of spontaneously (SHR) and desoxicorticosterone acetate (DOCA)-induced hypertensive rats and that of respective normotensive Wistar Kyoto (WKY) and Sprague-Dawley (SPRD) rats. For this we evaluated, ex vivo in liver cytosols, reduced glutathione (GSH) content, glutathione-related enzyme (peroxidase, reductase and transferase) activities as well as the rate of lipid peroxidation in 9–11 week-old rats. The antioxidant status and the cytotoxicity of acetaminophen, a radical- and hydrogen peroxide-mediated hepatotoxic compound, were also assessed in vitro in cultured hepatocytes isolated from hypertensive (SHR, DOCA) and normotensive control (WKY, SPRD) rats. Our results suggest that a difference exists in the hepatic antioxidant status between rat strains, with GSH levels being lower (–15%) and lipid peroxidation rate higher (+30%) in WKY compared to SPRD rats. In hepatocyte cultures from WKY rats, both GSH content and catalase activity were lower (–30 and –70% respectively) compared to hepatocyte cultures from SPRD rats. This was associated with a 35% higher cytotoxicity of acetaminophen in cultured hepatocytes from WKY rats compared to that in hepatocytes from SPRD rats. Hypertension in DOCA rats (mmHg: 221 ± 9 vs. 138 ± 5 in control SPRD rats) was associated with decreases (about 30%) in both glutathione peroxidase (GSH-Px) and catalase activities, ex vivo in livers and in vitro in hepatocyte cultures. Hypertension in SHR (mmHg: 189 ± 7 vs. 130 ± 5 in control WKY rats) was also associated with decreases (about 50%) in GSH-Px activity, ex vivo in livers and in vitro in hepatocyte cultures but catalase activity was not modified. The IC₅₀ of acetaminophen was also lower in hepatocytes from hypertensive rats compared to respective controls, which could be related to the weakened antioxidant status in hepatocytes from hypertensive rats. Our data thus suggest that hepatocyte cultures are appropriated tools in which to assess hepatotoxicity and hepatoprotection in hypertension.     

Targeted activation of transcription in vivo through hairpin-triplex forming oligonucleotide in Saccharomyces cerevisiae

The aims of the present study were to analyse the effects of an oral daily dose (10 mg/kg) of the dietary flavonoid quercetin for five weeks in two-kidney, one-clip (2K1C) Goldblatt (GB) hypertensive rats. The evolution of systolic blood pressure was followed by weekly measurements, and morphological variables, proteinuria, plasma nitrates plus nitrites (NO_x) and thiobarbituric acid reactive substances (TBARS), liver oxidative stress markers and endothelial function were determined at the end of the experimental period. Quercetin treatment reduced systolic blood pressure of GB rats, producing no effect in control animals. It also reduced cardiac hypertrophy and proteinuria developed in GB hypertensive rats. Decreased endothelium-dependent relaxation to acetylcholine of aortic rings from GB rats was improved by chronic quercetin treatment, as well as increased endothelium-dependent vasoconstrictor response to acetylcholine and overproduction of TXB₂ by aortic vessels of GB rats, being without effect in normotensive animals. Increased plasma NO_x and TBARS, and decreased liver total glutathione (GSH) levels and glutathione peroxidase (GPX) activity were observed in GB hypertensive rats compared to the control animals. Normalisation of plasma NO_x and TBARS concentrations and improvement of the antioxidant defences system in liver accompanied the antihypertensive effect of quercetin. We conclude that chronic oral treatment with quercetin shows both antihypertensive and antioxidant effects in this model of renovascular hypertension. (Mol Cell Biochem 270: 147–155, 2005)M.F. García-Saura and M. Galisteo are equal contributors to this work     

Effect of angiotensin II on energetics,glucose metabolism and cytosolic NADH/NAD and NADPH/NADP redox in vascular smooth muscle

We investigated the potential of chronic administration of an oral daily dose (10 mg/kg) of the dietary flavonoid quercetin to prevent hypertension and oxidative stress induced by deoxycorticosterone acetate (DOCA)-salt in rats. We have compared its effects to those produced by the well-known anti-hypertensive drug verapamil, administered orally (20 mg/kg/day). Quercetin and verapamil treatments reduced systolic blood pressure of DOCA-salt rats in approximately 67.6 and 63.3% respectively, producing no effect in control animals. Both drugs reduced significantly hepatic and renal hypertrophy induced by DOCA-salt administration, while only quercetin prevented cardiac hypertrophy. Decreased endothelium-dependent relaxation to acetylcholine of aortic rings from DOCA-salt-treated rats was improved by quercetin, but verapamil only enhanced it in the presence of superoxide dismutase (SOD) plus catalase. Increased plasma and heart thiobarbituric acid reactive substances (TBARS) and total glutathione (GSH) levels in liver and heart, decreased liver glutathione peroxidase (GPX) and liver and kidney glutathione transferase (GST) activities were observed in DOCA-salt-treated rats compared to the control animals. The antihypertensive effect of quercetin was accompanied by normalisation of plasma TBARS values, improvement of the antioxidant defences system in heart and liver, restoring total GSH levels in both organs and altered liver GST and GPX activities, and improving kidney GST activity. Verapamil treatment only restored GSH levels in heart, having no effect on other alterations induced by DOCA-salt chronic administration in the antioxidant defences analysed. In conclusion, quercetin shows both antihypertensive and antioxidant properties in this model of mineralocorticoid hypertension, while verapamil exhibits only antihypertensive effects.     

Effects of combined quercetin and coenzyme Q(10) treatment on oxidative stress in normal and diabetic rats

Reactive oxygen species may be actively involved in the genesis of various pathological states such as ischemia-reperfusion injury, cancer, and diabetes. Our objective was to determine if subacute treatment with combined antioxidants quercetin and coenzyme Q(10) (10 mg/kg/day ip for 14 days) affects the activities of antioxidant enzymes in normal and 30-day streptozotocin-induced diabetic Sprague-Dawley rats. Quercetin treatment raised blood glucose concentrations in normal and diabetic rats, whereas treatment with coenzyme Q(10) did not. Liver, kidney, heart, and brain tissues were excised and the activities of catalase, glutathione reductase, glutathione peroxidase, superoxide dismutase, and concentrations of oxidized and reduced glutathione were determined. In the liver of diabetic rats, superoxide dismutase, glutathione peroxidase, and levels of both oxidized and reduced glutathione were significantly decreased from the nondiabetic control, and these effects were not reversed when antioxidants were administered. In kidney, glutathione peroxidase activity was significantly elevated in the diabetic rats as compared to nondiabetic rats, and antioxidant treatment did not return the enzyme activity to nondiabetic levels. In heart, catalase activity was increased in diabetic animals and restored to normal levels after combined treatment with quercetin and coenzyme Q(10). Cardiac superoxide dismutase was lower than normal in quercetin- and quercetin + coenzyme Q(10)-treated diabetic rats. There were no adverse effects on oxidative stress markers after treatment with quercetin or coenzyme Q(10) singly or in combination. In spite of the elevation of glucose, quercetin may be effective in reversing some effects of diabetes, but the combination of quercetin + coenzyme Q(10) did not increase effectiveness in reversing effects of diabetes.     

L-carnitine attenuates oxidative stress in hypertensive rats

The present study aimed to investigate whether l-carnitine (LC) protects the vascular endothelium and tissues against oxidative damage in hypertension. Antioxidant enzyme activities, glutathione and lipid peroxidation were measured in the liver and heart of spontaneously hypertensive rats (SHR) and Wistar-Kyoto (WKY) rats. Nitrite and nitrate levels and total antioxidant status (TAS) were evaluated in plasma, and the expression of endothelial nitric oxide synthase (eNOS) and p22phox subunit of NAD(P)H oxidase was determined in aorta. Glutathione peroxidase activity was lower in SHR than in WKY rats, and LC increased this activity in SHR up to values close to those observed in normotensive animals. Glutathione reductase and catalase activities, which were higher in SHR, tended to increase after LC treatment. No differences were found in the activity of superoxide dismutase among any animal group. The ratio between reduced and oxidized glutathione and the levels of lipid peroxidation were respectively decreased and increased in hypertensive rats, and both parameters were normalized after the treatment. Similarly, LC was able to reverse the reduced plasma nitrite and nitrate levels and TAS observed in SHR. We found no alterations in the expression of aortic eNOS among any group; however, p22phox mRNA levels showed an increase in SHR that was reversed by LC. In conclusion, chronic administration of LC leads to an increase in hepatic and cardiac antioxidant defense and a reduction in the systemic oxidative process in SHR. Therefore, LC might increase NO availability in SHR aorta by a reduction in superoxide anion production.     

Increased Oxidative Parameters and Decreased Cytokine Levels in an Animal Model of Attention-Deficit/Hyperactivity Disorder

Attention-deficit/hyperactivity disorder (ADHD) is a highly heterogeneous disorder characterized by impairing levels of hyperactivity, impulsivity and inattention. Oxidative and inflammatory parameters have been recognized among its multiple predisposing pathways, and clinical studies indicate that ADHD patients have increased oxidative stress. In this study, we aimed to evaluate oxidative (DCFH oxidation, glutathione levels, glutathione peroxidase, catalase and superoxide dismutase activities) and inflammatory (TNF-α, IL-1β and IL-10) parameters in the most widely accepted animal model of ADHD, the spontaneously hypertensive rats (SHR). Prefrontal cortex, cortex (remaining regions), striatum and hippocampus of adult male SHR and Wistar Kyoto rats were studied. SHR presented increased reactive oxygen species (ROS) production in the cortex, striatum and hippocampus. In SHR, glutathione peroxidase activity was decreased in the prefrontal cortex and hippocampus. TNF-α levels were reduced in the prefrontal cortex, cortex (remaining regions), hippocampus and striatum of SHR. Besides, IL-1β and IL-10 levels were decreased in the cortex of the ADHD model. Results indicate that SHR presented an oxidative profile that is characterized by an increase in ROS production without an effective antioxidant counterbalance. In addition, this strain showed a decrease in cytokine levels, mainly TNF-α, indicating a basal deficit. These results may present a new approach to the cognitive disturbances seen in the SHR.     

Effect of chromium supplementation on the diabetes induced-oxidative stress in liver and brain of adult rats

This study was designed to investigate the susceptibility of liver and brain tissues, as insulin-independent tissues, of normal adult male rats to the oxidative challenge of subchronic supplementation with chromium picolinate (CrPic) at low (human equivalent) and high doses (2.90 and 13.20 μg Cr kg⁻¹ day⁻¹, respectively). Also, the modulative effect of CrPic administration on the enhanced oxidative stress in the liver and brain tissues of alloxan-diabetic rats was studied. Fasting serum glucose level was not modified in normal rats but significantly reduced in diabetic rats that had received CrPic supplement. A mild oxidative stress was observed in the liver and brain of CrPic-supplemented normal rats confirmed by the dose-dependent reductions in the levels of hepatic and cerebral free fatty acids, superoxide dismutase and glutathione peroxidase activities, and in contrast increased tissue malondialdehyde concentration. On the other hand, hepatic and cerebral catalase activity was reduced in the high dose group only. CrPic supplementation did not act as a peroxisome proliferator confirmed by the significant reductions in liver and brain peroxisomal palmitoyl CoA oxidase activity. The non significant alterations in liver protein/DNA and RNA/DNA ratios indicate that CrPic did not affect protein synthesis per cell, and that mild elevations in hepatic total protein and RNA concentrations might be due to block or decrease in the export rate of synthesized proteins from the liver to the plasma. In diabetic rats, elevated levels of hepatic and cerebral free fatty acids and malondialdehyde, and in contrast the overwhelmed antioxidant enzymes, were significantly modulated in the low dose group and near-normalized in the high dose group. The significant increases observed in liver total protein and RNA concentrations, as well as protein/DNA and RNA/DNA ratios in diabetic rats supplemented with the high dose of Cr, compared to untreated diabetics, may be related to the improvement in the glycemic status of the diabetic animals rather than the direct effect of CrPic on protein anabolism.     

Plasma catecholamines and dopamine-beta-hydroxylase activity in spontaneously hypertensive rats.

Levels of plasma norepinephrine and total catecholamines in spontaneously hypertensive rats bred from a normotensive Kyoto strain of Wistar rats increase between their 8th to 12th week post utero concomitant with the development of hypertension, but levels of plasma norepinephrine are not significantly different between the spontaneously hypertensive strain, a normotensive Kyoto strain and a N.I.H. strain of Wistar rats at either 8 or 12 weeks of age. Plasma total catecholamine levels in the spontaneously hypertensive strain are significantly higher at 12 weeks of age than those in either control strain, while plasma levels of dopamine-β-hydroxylase show no consistant relationship between the three strains. It, therefore, appears unlikely that increased sympathetic neuronal activity is an etiological factor in this form of hypertension.     

Moderate red wine consumption protects the rat against oxidation in vivo.

The effect of the moderate consumption of red wine on the antioxidant system in rat liver, kidney and plasma has been evaluated. Wistar rats were treated in separate groups as follows: control; red wine for 45 days or 6 months; and 13.5% ethanol for 45 days or 6 months. The consumption of alcoholic beverages was free because the rat could always choose between the alcoholic beverage and the water. In liver, red wine ingestion resulted in higher hepatic superoxide dismutase and glutathione peroxidase activities after 45 days of treatment. The data indicate that wine and ethanol ingestion resulted in lower hepatic malondialdehyde and enhanced hepatic catalase activity in both of the periods studied. In kidney, the reduced glutathione/oxidized glutathione ratio was higher after 45 days of wine consumption, and the malondialdehyde was lower after 6 months of wine consumption. In plasma, malondialdehyde was lower after 6 months of both treatments, but plasmatic vitamin E was higher after red wine consumption while it was lower after ethanol consumption for this period of time. The present study shows that the moderate and prolonged consumption of red wine is consistent with higher protection against oxidation in vivo.     

Serum IGF-1 levels correlate negatively to liver damage in diabetic rats

Abstract

Diabetes and insulin resistance frequently cause liver damage. Diabetes also causes reduction in liver and blood IGF-1 levels. We investigated the relation between liver damage and IGF-1 levels in diabetic rats. Fourteen Wistar albino rats were divided into control and diabetic groups. Diabetes was induced by streptozotocin. Rats were sacrificed for biochemical and histologic examinations 2 weeks after streptozotocin injection. Serum and liver IGF-1 levels were decreased, liver malondialdehyde (MDA) levels were increased, glutathione peroxidase (GPx) enzymes activities were decreased and serum alanine aminotransferase (ALT) levels were increased in diabetic group. Microscopic examination of liver revealed that normal tissue organization was disrupted in streptozotocin-induced diabetic rats. There was a strongly positive correlation between blood glucose levels and liver injury, and blood and liver IGF-1 levels. There was a strongly negative correlation between blood IGF-1 levels and hepatic injury. Our results suggest that reduction of blood IGF-1 levels correlates with hepatic injury and circulating IGF-1 levels may have predictive value for determining hepatic damage that results from diabetes. In addition, circulating IGF-1 levels are correlated with glutathione levels and the oxidative stress status of diabetic rat liver.     

Action of E. coli endotoxin,IL-1β and TNF-α on antioxidant status of cultured hepatocytes

We have previously reported that endotoxin induces in vivo oxidative stress in liver and a significant increase in hepatic and plasma glutathione concentrations during the acute phase of reversible endotoxic shock in rats. In the present study we examined the in vitro effects of E. coli 0111:B4 endotoxin (lipopolysaccharide, LPS), IL-1 and TNF- on antioxidant status of cultured hepatocytes in order to differentiate between the direct and mediated endotoxin action. LPS increased total glutathione (tGSH) levels after 2 h treatment but decreased oxidized glutathione (GSSG) content which lead to a marked decrease in GSSG/tGSH index. At shorter treatment times a biphasic and dose-dependent behaviour was observed. Cytokines (IL-1 and TNF-) produced significant decreases in tGSH and GSSG after 30 min treatment. Despite its prooxidant effect, TNF- significantly reduced GSSG/tGSH index. Although no significant effects were observed on glutathione reductase activity, both LPS and cytokines induced an important inhibition of glutathione peroxidase which can justify the lipid peroxidation previously observed both in liver during reversible endotoxic shock and in cultured hepatocytes after treatment with endotoxin. The inhibition of hepatic glutathione peroxidase, besides the stimulation of GSH synthesis by LPS and GSH efflux by cytokines, guarantees the export of hepatic glutathione in its reduced form for other organs, contributing to the interorgan homeostasis. On the other hand, the results presented here support a new role for GSSG/tGSH index different from a mere indicator of oxidative stress.     

The effect of age and selenium on some biochemical parameters in rat liver

Two age groups, 3 and 15 mo, were used to investigate whether age-associated changes in some parameters related to lipid peroxidation occur in the liver of male Wistar rats and to observe possible effects of dietary selenium supplementation (0.25 and 0.50 ppm) for 12 mo on the same parameters. At these experimental conditions, the most important observation was that peroxidation did not change by aging, at least until 15 mo of age. In addition, the activity of Sedependent glutathione peroxidase (GSH-Px, EC 1.11.1.9) was higher in the liver of the older animals. It is suggested that the enzyme could have a role in the unchanged hepatic peroxidation observed in aged male rats. On the other hand, an effect of dietary selenium supplementation on those parameters was not observed, probably because the selenium levels were still at an adequate plateau.     

Low-carbohydrate diet and oxidative stress in diabetic and nondiabetic rats

Hyperglycemia of diabetes has been implicated in increased tissue oxidative stress, with consequent development of secondary complications. Thus, stabilizing glucose levels near normal levels is of utmost importance. Because diet influences glycemic control, this study investigated whether a low-carbohydrate (5.5%) diet confers beneficial effects on the oxidative status of the heart, kidney, and liver in diabetes. Male and female normal and diabetic rats were fed standard chow (63% carbohydrates) or low-carbohydrate diet for 30 days. Elevated glucose, HbA(1c), and alanine and aspartate aminotransferases in diabetic animals were reduced or normalized by the low-carbohydrate diet. While diabetes increased cardiac activities of glutathione peroxidase and catalase, low-carbohydrate diet normalized cardiac glutathione peroxidase activity in diabetic animals, and reduced catalase activity in females. Diabetic rats fed low-carbohydrate diet had altered activities of renal glutathione reductase and superoxide dismutase, but increased renal glutathione peroxidase activity in diabetic animals was not corrected by the test diet. In the liver, diabetes was associated with a decrease in catalase activity and glutathione levels and an increase in glutathione peroxidase and gamma-glutamyltranspeptidase activities. Decreased hepatic glutathione peroxidase activity and lipid peroxidation were noted in diet-treated diabetic rats. Overall, the low-carbohydrate diet helped stabilize hyperglycemia and did not produce overtly negative effects in tissues of normal or diabetic rats.