Effect of bacterial lipopolysaccharide on the content of lipid peroxidation products in lungs and other organs of mice

The influence of lipopolysaccharide fromEscherichia coli (LPS, 17 mg/kg body weight) on the lipid peroxidation process in organs of mice was studied. The content of conjugated dienes (CD), lipid peroxides (LP), malondialdehyde (MDA) (all three lipid peroxidation by-products), peroxidase (PO) activity and wet-to-dry weight ratio in lungs, heart, spleen, kidneys and liver were determined 1.5 h after intravenous injection of LPS. Animals observed at this time-point had reduced activity and decreased body temperature by about 2°C, however, all analysed organs did not reveal any changes of wet-to-dry weight ratio comparing to organs from mice injected with sterile, pyrogen free 0,9% NaCl. Only extracts from heart and lungs showed significant increase in the tissue level of at least two lipid peroxidation products. The heart content of CD, MDA, and LP was about 1.5-, 1.3-, and 2.4-fold higher than in control group. In lungs CD and MDA increased 3.3- and 1.3-times but in spleen only content of LP was elevated. In these organs the suppression of PO activity was also observed. Liver and kidneys did not reveal any convincing enhancement of lipid peroxidation process and alterations of PO activity. Since free radical reactions are involved in lipid peroxidation process and inactivation of PO these results suggest that heart, lungs and spleen are the organs mostly exposed to oxidative stress during the first 1.5 h after single injection of LPS in mice.Abbreviations CD conjugated dienes - LP lipid peroxides - LPS lipopolysaccharide - MDA malondialdehyde - PMNL polymorphonuclear leukocytes - PO peroxidase - TBA thiobarbituric acid     

Lipid peroxidation in isolated hepatocytes.

Intracellular lipid peroxidation was initiated by the addition of ADP-complexed ferric iron to isolated rat hepatocytes and the reaction monitored by the thiobarbituric acid method or by measurement of the formation of conjugated dienes. Both the production of malondialdehyde (thiobarbituric-acid-reacting substances) and of conjugated dienes was dependent, on the ADP-Fe-3+ concentration in a dose-related fashion. Malondialdehyde formation stopped spontaneously within 20 min after the initiation of the reaction and the plateau reached was also related to the ADP-Fe-3+ concentration. Control experiments revealed that more than 90% of the malondialdehyde accumulating during the incubation period could be ascribed to intracellular production. The cellular NADPH/NADP+ ratio was always high and only slightly decreased upon ADP-Fe-3+-induced lipid peroxidation which, however, was associated with a marked decrease in the cellular glutathione concentration. The rate of accumulation of malondialdehyde as well as the final level reached during ADP-Fe-3+-initiated lipid peroxidation was increased by the addition of chloral hydrate. This apparent stimulatory effect could, however, be ascribed to the inhibition of the mitochondrial oxidation of the malondialdehyde formed during cellular lipid peroxidation, thus allowing more malondialdehyde to accumulate during the process. ADP-Fe-3+-induced cellular lipid peroxidation was associated with a decrease in the concentration of glutathione. Also, lowering of the intracellular glutathione level by the addition of diethyl maleate or by simply preincubating the hepatocytes (up to 50 min) promoted the ADP-Fe-3+ malondialdehyde production and formation of conjugated dienes. Furthermore, when cellular glutathione concentration had been lowered by preincubation of the hepatocytes, significant malondialdehyde production could be observed even at ADP-Fe-3+ concentrations which were too low to induce measurable lipid peroxidation in fresh hepatocytes. It is thus concluded that glutathione has an important role in the cell defence against lipid peroxidation and suggested that the isolated hepatocytes provide a suitable experimental model system for the characterization of this and other possible cellular defence mechanisms and how they are affected by the nutritional status of the donor animal.     

Effect of polyethylene glycol on lipid peroxidation in cold-stored rat hepatocytes

A mechanism suggested to cause injury to preserved organs is the generation of oxygen free radicals either during the cold-storage period or after transplantation (reperfusion). Oxygen free radicals can cause peroxidation of lipids and alter the structural and functional properties of the cell membranes. Methods to suppress generation of oxygen free radicals of suppression of lipid peroxidation may lead to improved methods of organ preservation. In this study we determined how cold storage of rat hepatocytes affected lipid peroxidation by measuring thiobarbituric acid reactive products (malondialdehyde, MDA). Hepatocytes were stored in the UW solution +/- glutathione (GSH) or +/- polyethylene glycol (PEG) for up to 96 h and rewarmed (resuspended in a physiologically balanced saline solution and incubated at 37 degrees C under an atmosphere of oxygen) after each day of storage. Hepatocytes rewarmed after storage in the UW solution not containing PEG or GSH showed a nearly linear increase in MDA production with time of storage and contained 1.618 +/- 0.731 nmol MDA/mg protein after 96 h. When the storage solution contained PEG and GSH there was no significant increase in MDA production after up to 72 h of storage and at 96 h MDA was 0.827 +/- 0.564 nmol/mg protein. When freshly isolated hepatocytes were incubated (37 degrees C) in the presence of iron (160 microM) MDA formation was maximally stimulated (3.314 +/- 0.941 nmol/mg protein). When hepatocytes were stored in the presence of PEG there was a decrease in the capability of iron to maximally stimulate lipid peroxidation. The decrease in iron-stimulated MDA production was dependent upon the time of storage in PEG (1.773 nmol/mg protein at 24 h and 0.752 nmol/mg protein at 48 h).(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of melatonin on oxidative status of rat brain, liver and kidney tissues under constant light exposure

An enormous amount of data has been published in recent years demonstrating melatonin's defensive role against toxic free radicals. In the present study, we examined the role of melatonin as an antioxidant against the effect of continuous light exposure. Rats were divided into three groups. Control rats (group A) were kept under natural conditions whereas other group of rats (group B and C) were exposed to constant light for inhibition of melatonin secretion by the pineal gland. Group C rats also received melatonin via s.c. injection (1 mg x kg(- 1) body weight x day(- 1)). At the end of experiment, all animals were sacrificied by decapitation, serum and tissue samples were removed for determination of malondialdehyde (MDA), a product of lipid peroxidation, conjugated dienes levels and glutathione peroxidase (GSH-Px) activity levels. It was found that lipid peroxidation was increased in the rats which were exposed to constant light. Melatonin injection caused a decrease in lipid peroxidation, especially in the brain. In addition, melatonin application resulted in increased GSH-Px activity, which has an antioxidant effect. Thus, melatonin is not only a direct scavenger of toxic radicals, but also stimulates the antioxidative enzyme GSH-Px activity to detoxify hydroxyl radical produced by constant light exposure.     

The effect of Ca2+ on the thermal stability of trypsin in phosphate-buffered saline solution used for harvesting of human embryonic lung fibroblast cultures

The stabilizing effect of Ca2+ (264.9 mg CaCl2 X 2H2O ml-1) on a 0.5% solution of twice-crystallized bovine trypsin in phosphate-buffered saline (used for harvesting human embryonic lung fibroblasts) was studied at 7-37 degrees C and at -20 and -70 degrees C. It can be concluded that storage of the enzyme in the buffer (with or without Ca2+) is not advisable at temperatures greater than or equal to 20 degrees C. At 7 degrees C, on the other hand, trypsin can be stored for some weeks in the calcium-containing phosphate-buffered saline if a moderate loss of activity is acceptable. At -20 degrees C and -70 degrees C the stability of the enzyme was good. In the presence of Ca2+ about 90% of the activity remained after 18 weeks. Without Ca2+ the activity was approximately 10% lower.     

Reduced vulnerability of the hypertrophied rat heart to oxygen-radical injury

Effects of xanthine--xanthine oxidase produced oxygen radicals were studied in hypertrophied rat hearts in a Langendorff preparation. Heart hypertrophy was produced by banding of the abdominal aorta for 6 weeks. This resulted in a 22% increase in ventricle/body weight ratio compared with that of sham-operated controls. Perfusion with xanthine--xanthine oxidase caused contractile failure and a significant rise in the resting tension. Complete contractile failure in hypertrophied hearts was seen at 25.5 +/- 3.2 min, whereas in control hearts it happened at 14.4 +/- 5.6 min. Contractile failure due to oxygen radicals in both groups was associated with a decline in high energy phosphates, increased lipid peroxidation, and extensive structural damage. Sarcolemma in both groups became permeable to the extracellular tracer lanthanum. As compared with control, in hypertrophied hearts the malondialdehyde content, indicative of lipid peroxidation, was less by 40%; whereas superoxide dismutase, a free radical scavenger, was higher by a similar amount. These data show a greater capacity of the 6-week hypertrophied heart to withstand a free radical induced contractile failure. This delay in oxygen radical effect can be partially explained by the reduced lipid peroxide content and increased superoxide dismutase activity in the hypertrophied hearts.     

Potentiation of lipid peroxides by ischemia in rat brain

Post-ischemic changes in energy metabolites and natural antioxidant compounds have been measured in rat brain in vitro concurrent with two different assays for peroxidized lipids. No exogenous free radical initiators were employed. In vitro oxygenation of minced brain preparations for periods of 10 minutes to 4 hours, following 5 minutes of preparatory ischemia, yielded increased levels of lipid conjugated dienes and TBA-reactive material, in contrast to anaerobically incubated preparations. However, either aerobic or anaerobic incubation of brain minces facilitated increased ratios of lactate: pyruvate and glutathione (oxidized): glutathione (reduced), as well as increased total ubiquinone content and loss of -tocopherol. Observation of lipid radical formation in vivo was then attempted using rats given embolic stroke in one hemisphere and left in the post-ischemic condition for times up to 24 hours. Conjugated dienes were found in lipids extracted from the ipsilateral hemisphere but not from the contralateral hemisphere. These observations of conjugated dienes in vivo (formed presumably during post-ischemic reperfusion) and in vitro (facilitated by oxygenation of brain minces), indicate that lipid radical intermediates and associated chain peroxidation processes are potentiated by ischemia and occur during tissue reoxygenation.     

Effect of thyroidectomy and adrenalectomy on changes in liver glutathione and malonaldehyde levels after acute ethanol injection

At low concentrations ethanol is metabolized largely by alcohol dehydrogenase to acetaldehyde, while at higher concentrations a microsomal ethanol oxidising system (MEOS) is involved, namely cytochrome P450 IIE1, which also probably generates free radical species. In hyperthyroidism hepatic glutathione stores are depleted and net superoxide anion production occurs. In contrast, in hypothyroidism hepatic glutathione may be increased and thus renders the liver less sensitive to alcohol generated free radical production. Steroid hormones inhibit lipid peroxidation. Sixty male Wistar rats either underwent thyroidectomy, adrenalectomy, or sham procedures. Twenty control animals were pair fed with thyroidectomized animals, whilst another twenty fed ad libitum. An intraperitoneal injection of alcohol (75 mmol/kg) was given 2.5 h prior to sacrifice to half the animals in each group, the remainder receiving saline. The total hepatic glutathione contents of the pair fed and the ad libitum groups were not different, but were significantly increased by thyroidectomy (p = <0.001). This effect was significantly reduced by alcohol (p < 0.01). The sham procedures and dietary restrictions had no effect. The ethanol alone reduced total hepatic glutathione, but this only reached statistical significance in the thyroidectomized and sham-adrenalectomized groups. Hepatic malonaldehyde (MDA) levels were significantly reduced in the thyroidectomy group but alcohol had no effect on them. We conclude that hypothyroidism increased hepatic glutathione status, presumably by reducing radical production by enzyme systems, which would otherwise consume this important scavenger. Long term exposure to ethanol with induction of MEOS is probably required for it to generate toxic levels of free radical species.     

Free radical scavenging as affected by accelerated ageing and subsequent priming in sunflower seeds

Lipid peroxidation resulting from loss of free radical scavenging is thought to be involved in deterioration of sunflower (Helianthus annuus L.) seeds during accelerated ageing. In other respects, presoaking of seeds in a solution of low water potential (osmopriming) has been demonstrated to reinvigorate aged seeds. The aim of the present work was to study the effect of osmopriming on the germination of aged sunflower seeds and to investigate whether this effect was associated with the restoration of antioxidant defence systems. Seeds were aged for 5 days at 45°C and 100% relative humidity and then primed for various durations up to 7 days at 15°C in a solution of polyethylene glycol 6000 at ?2 MPa. Lipid peroxidation was estimated by measuring malondialdehyde (MDA) and conjugated diene contents, and the activities of superoxide dismutase (SOD), catalase (CAT), glutathione reductase (GR), ascorbate peroxidase (APX) and dehydroascorbate reductase (DHAR) were measured throughout the treatments. Accelerated ageing resulted in a marked decrease in the germination rate, and was associated with an increase in the levels of MDA and conjugated dienes, thus indicating lipid peroxidation. Ageing was also characterized by a decrease in the activities of CAT and GR. The activities of SOD and DHAR were much less altered. No APX activity was detected whatever the seed treatment. Priming of aged seeds progressively restored the initial germinative ability and resulted in a marked decrease in the levels of MDA and conjugated dienes, indicating a fall in lipid peroxidation processes. These effects of priming were also well correlated to the recovery of SOD, CAT and GR activities. Priming treatment for 7 days led to full restoration of the cell detoxifying mechanisms which were strongly altered during ageing. Glutathione content showed the same changes as GR activity. There existed a clear-cut relationship between seed germinative energy, expressed as the germination rate, and the efficiency of free radical scavenging systems, in particular CAT and GR activities and glutathione content. The results suggest that the antioxidant defence systems might play a key role in seed vigour.     

Physical exercise, oxidative stress and muscle damage in racehorses

Since it has been suggested that lipid peroxidation following free radical overproduction may be one of the causes of physical exercise-induced myopathies and hemolysis in horses, we looked for the possible relationships between these phenomena and muscle fiber damage. We use a homogeneous group of Maremmana stallions which, after a 3-month training period, underwent a series of physical exercises of increasing intensity. We determined the contents of malondialdehyde (MDA), one of the main lipid peroxidation end-products, and glutathione the substrate of one of the most important free radical scavenger enzymes. We also measured creatine phosphokinase and serum lactate dehydrogenase isoenzyme activities whose modification may be indicative of muscle fiber damage. The results obtained indicated that the physical exercise we adopted was able to modify both MDA and glutathione contents in blood. However, its effect on some LDH isoenzyme activities suggested possible damage to tissues other than muscle.     

Zinc suppression of free radicals induced in cultures of rat hepatocytes by iron, t-butyl hydroperoxide, and 3-methylindole

The effect of zinc on lipid peroxidation initiated by either ferric-nitrilotriacetate, t-butyl hydroperoxide, or 3-methylindole was studied using primary monolayer cultures of rat liver parenchymal cells. The malondialdehyde content of the cells and culture medium was used to estimate the extent of lipid peroxidation. As the zinc concentration of the culture medium was increased from 1 to 48 microM, peroxidation was diminished. Cellular zinc and metallothionein levels were proportionally increased by supplemental zinc. Zinc supplementation of the medium inhibited NADPH-cytochrome c reductase activity and stimulated glutathione peroxidase activity. The uptake of iron into the hepatocytes was significantly reduced as the level of zinc was raised, suggesting that zinc antagonizes uptake of chelated iron into isolated hepatocytes and in this way blocks iron-induced peroxidation. Furthermore, induction of metallothionein synthesis by zinc may contribute to the reduction in free radicals. Spectra from electron spin resonance studies, using phenylbutylnitrone as a spin-trapping reagent, demonstrated that free radical production was inversely related to the zinc concentration of the culture medium. Spin trap data suggest that metallothionein added to lysed cells in vitro decreases free radical production. Studies using the spin trap, 3,3,5,5-tetramethylpyrroline-N-oxide indicated that cumulatively the predominant radical present in the cultures was a phenyl radical with hydroperoxide or methylindole. Collectively, our data demonstrate that zinc inhibits free radical production and lipid peroxidation in cultured hepatocytes. The mode of action of zinc could occur via free radical scavenging by zinc-induced metallothionein and/or by processes related to cytochrome P-450 and glutathione peroxidase, since these were also found to be sensitive to zinc supplementation levels of the culture medium.     

Biochemical and immunological changes on oral glutamate feeding in male albino rats

 High altitude stress leads to lipid peroxidation and free radical formation which results in cell membrane damage in organs and tissues, and associated mountain diseases. This paper discusses the changes in biochemical parameters and antibody response on feeding glutamate to male albino Sprague Dawley rats under hypoxic stress. Exposure of rats to simulated hypoxia at 7576 m, for 6 h daily for 5 consecutive days, in an animal decompression chamber at 32±2° C resulted in an increase in plasma malondialdehyde level with a concomitant decrease in blood glutathione (reduced) level. Supplementation of glutamate orally at an optimal dose (27 mg/kg body weight) in male albino rats under hypoxia enhanced glutathione level and decreased malondialdehyde concentration significantly. Glutamate feeding improved total plasma protein and glucose levels under hypoxia. The activities of serum glutamate oxaloacetate transaminase (SGOT) and serum glutamate pyruvate transaminase (SGPT) and the urea level remained elevated on glutamate supplementation under hypoxia. Glutamate supplementation increased the humoral response against sheep red blood cells (antibody titre). These results indicate a possible utility of glutamate in the amelioration of hypoxia-induced oxidative stress. Received: 23 March 1998 / Accepted: 19 October 1998     

The effect of silibinin (Legalon) on the the free radical scavenger mechanisms of human erythrocytes in vitro.

The effect of Legalon was investigated parallel with that of Adriblastina (doxorubicin) and paracetamol on some parameters characterizing the free radical scavenger mechanisms of human erythrocytes in vitro and on the time of acid hemolysis performed in aggregometer. Observations suggest that Adriblastina enhances the lipid peroxidation of the membrane of red blood cells, while paracetamol causes significant depletion of intracellular glutathione level, thus decreasing the free radical eliminating capacity of the glutathione peroxidase system. Legalon on the other hand, is able to increase the activity of both superoxide dismutase and glutathione peroxidase, which may explain the protective effect of the drug against free radicals and also the stabilizing effect on the red blood cell membrane, shown by the increase of the time of full haemolysis.     

Lead-catalyzed peroxidation of essential unsaturated fatty acid

In the present study, the reaction mixtures (lead compounds with essential unsaturated fatty acids) were preincubated at 37°C for 24 h prior to the measurement of malondialdehyde (MDA) by HPLC. The metal-catalyzed reactions were also compared in the presence of butylated hydroxytoluene (BHT), a free radical scavenger. Our results showed that according to the difference in the number of double bonds of essential unsaturated fatty acids, the kinds of lead compounds, and the concentrations of lead compounds, the extent of lipid peroxidation was different. The addition of BHT to the reaction mixtures significantly reduced the production of MDA (P<0.01). These in vitro studies support prior in vivo reports that the important mechanism of the acute toxic effects of the lead compounds is owing at least in part, to metal-catalyzed peroxidation of polyun-saturated fatty acids.     

Reduced susceptibility to lipid peroxidation in cold ischemic rabbit kidneys after addition of desferrioxamine, mannitol, or uric acid to the flush solution

Rabbit kidneys were stored for 24 hr at 0 degree C after single passage arterial flush with 30 ml of cold isotonic 0.9% sodium chloride (saline) solution alone or saline to which was added 12, 30, or 60 mM desferrioxamine, 1 or 3 mM uric acid, or 100 mM mannitol. They were then subjected to in vitro biochemical assay for evidence of free radical damage immediately after storage. Results were compared to those obtained with fresh, unstored kidneys. Levels of Schiff base fluorescence, diene conjugates, and thiobarbituric acid-reactive material were each significantly elevated in kidneys stored for 24 hr after flush with saline alone. These levels were in turn each significantly reduced by the addition of 60 mM desferrioxamine, 3 mM uric acid, and 100 mM mannitol to the flush solution. Likewise, glutathione redox activity fell in those flushed with saline alone, presumably in line with increased lipid peroxidation, but was restored to control levels by inclusion of the three scavenging agents.     

Free radical activity, antioxidant enzyme, and glutathione changes with muscle stretch injury in rabbits.

The present study investigated changes in rate of free radical production, antioxidant enzyme activity, and glutathione status immediately after and 24 h after acute muscle stretch injury in 18 male New Zealand White rabbits. There was no change in free radical production in injured muscles, compared with noninjured controls, immediately after injury (time 0; P = 0.782). However, at 24 h postinjury, there was a 25% increase in free radical production in the injured muscles. Overall, there was an interaction (time and treatment) effect (P = 0.005) for free radical production. Antioxidant enzyme activity demonstrated a treatment (injured vs. control) and interaction effect for both glutathione peroxidase (P = 0.015) and glutathione reductase (P = 0.041). There was no evidence of lipid peroxidation damage, as measured by muscle malondialdehyde content. An interaction effect occurred for both reduced glutathione (P = 0.008) and total glutathione (P = 0.015). Morphological analysis (hematoxylin and eosin staining) showed significant polymorphonuclear cell infiltration of the damaged region at 24 h postinjury. We conclude that acute mechanical muscle stretch injury results in increased free radical production within 24 h after injury. Antioxidant enzyme and glutathione systems also appear to be affected during this early postinjury period.     

Effect of Chronic N-Acetyl Cysteine Administration on Oxidative Status in the Presence and Absence of Induced Oxidative Stress in Rat Striatum

Antioxidants have possible therapeutic value in neurodegenerative disorders, although they may have pro-oxidant effects under certain conditions. Glutathione (GSH) is a key free radical scavenger. N-acetylcysteine (NAC) bolsters GSH and intracellular cysteine and also has effective free radical scavenger properties. The effects of chronic NAC administration (50 mg/kg/day, 500 mg/kg/day, 1500 mg/kg/day × 21 days) on cellular markers of oxidative status was studied in striatum of healthy male Sprague-Dawley rats as well as in animals with apparent striatal oxidative stress following chronic haloperidol treatment (1.5 mg/kg/day × 3 weeks). In non-haloperidol treated animals, NAC 50 and 500 mg/kg did not affect oxidative status, although NAC 1,500 mg/kg significantly increased striatal superoxide levels, decreased lipid peroxidation and increased consumption of reduced glutathione (GSH). Haloperidol alone evoked a significant increase in superoxide and lipid peroxidation. All NAC doses blocked haloperidol induced increases in superoxide levels, while NAC 500 mg/kg and 1,500 mg/kg prevented haloperidol-associated lipid peroxidation levels and also increased the GSSG/GSH ratio. NAC may protect against conditions of striatal oxidative stress, although possible pro-oxidative actions at high doses in otherwise healthy individuals, e.g. to offset worsening of neurodegenerative illness, should be viewed with caution.     

Oxidation of linoleyl alcohol by potato tuber lipoxygenase: kinetics and positional, stereo, and geometrical (cis, trans) specificity of the reaction

The dioxygenation of linoleyl alcohol (LAL) by potato tuber lipoxygenase leads to formation of two positional isomeric products--9- and 13-hydroperoxyoctadecadien-1-ols (Butovich, I. A., Luk'yanova, S. M., and Reddy, C. C. (1998) Biochem. Biophys. Res. Commun. 249, 344-349). In the present study, we examined the stereospecificity and double-bond conformation of primary dioxygenation products of LAL catalyzed by potato lipoxygenase. In contrast to the product profiles of linoleic acid oxidation by potato lipoxygenase, oxidation of LAL led to all possible positional (9- and 13-), stereo, and geometrical (cis,trans and all-trans) isomers in equimolar mixtures at 25 degrees C. The reaction appears to proceed through an enzyme-catalyzed formation of a pentadiene carbon-centered radical followed by resonance stabilization of the radical and molecular oxygen insertion in an enzyme-dependent as well as an enzyme-independent pathway. A strict positional, stereo, and geometrical specificity of the dioxygenation products of LAL oxidation appears to be maintained when the reaction occurs at the active site of the enzyme. However, when the pentadiene carbon-centered radical of LAL is dissociated from the active site of the enzyme, it appears to be nonenzymatically transformed into a mixture of all possible positional and geometrical stereoisomers of primary dioxygenation products. The latter pathway was effectively blocked by the free radical scavenger 4-hydroxy-TEMPO, which substantially reduced the production of all-trans hydroperoxyoctadecadienols. In the presence of the scavenger, 9(S)-hydroperoxy-10E,12Z-octadecadien-1-ol was the predominant LAL oxidation product, representing approximately 80% of the total conjugated dienes, with 13(S)-hydroxy-9Z,11E-octadecadien-1-ol the expected product of reverse orientation of the substrate at the active site, accounting for approximately 10%. A similar pattern in oxidation of LAL was observed when the reactions were carried out at 0 degrees C.     

Inhibitory effect of the flavonoid silymarin on the erythrocyte hemolysis induced by phenylhydrazine

The flavonoid silymarin, which is used as a therapeutical agent in the treatment of liver diseases, can inhibit the hemolysis and lipid peroxidation induced by phenylhydrazine on erythrocytes obtained from rats treated with the flavonoid. This effect is ascribed to the antioxidant properties as a free radical scavenger exhibited by the flavonoid. Silymarin failed to inhibit the glutathione depletion induced by phenylhydrazine on erythrocytes. It is proposed that the flavonoid acts at the membrane level of the cell avoiding the lipid peroxidative and fluidizing effect of phenylhydrazine.     

Increased Oxidant Stress and Decreased Antioxidant Status in Erythrocytes of Rats Fed with Zinc-deficient Diet

The aim of this study was to evaluate the lipid peroxidation, nitric oxide (NO), and free radical scavenging enzyme activities in erythrocytes of zinc (Zn)-deficient rats and to investigate the relationship among these parameters in either group. Sixteen male rats with a weight of 40-50 g were used for the experiment. The rats were divided into control (n = 8) and Zn-deficient groups. At the end of the experiment, the animals were anesthetized with ketamine-HCl (Ketalar, 20 mg/kg(-1), i.p.), and the blood was collected by cardiac puncture after thoracotomy. Blood samples were collected in vacutainer tubes without and with K(3)-EDTA as anticoagulant. Erythrocyte catalase (CAT), glutathione peroxidase (GSH-Px), glutathione reductase (GRD), glutathione-S-transferase (GST), superoxide dismutase (SOD) activities, total (enzymatic plus nonenzymatic) superoxide scavenger activity (TSSA), nonenzymatic superoxide scavenger activity (NSSA), antioxidant potential (AOP), and serum zinc (Zn) values in the Zn-deficient group were significantly lower than those of the control group, whereas NO and malondialdehyde (MDA) levels were significantly higher than those of the control group. The results show that Zn deficiency causes a decrease in antioxidant defense system and an increase in oxidative stress in erythrocyte of rats.