Selenium Glutathione Peroxidase Research Articles

Diet Supplementation with Pomegranate Peel Improves Embryonic Survival in a Mouse Model of Early Pregnancy Loss

The peel of pomegranate fruit is a rich source of polyphenolic compounds with powerful antioxidant properties. We evaluated the therapeutic potential of pomegranate peel (PP) in the prevention of early pregnancy loss in a mouse model of embryonic mortality and abortion (female CBA/J x male DBA/2). CBA/J mice were divided into 3 groups: mice in control group (CONT group) were fed a standard diet, whereas mice in groups 2 and 3 were fed a standard diet supplemented with 1% PP (PP1% group) and 5% PP (PP5% group), respectively. All the mice were fed their diets for 10 days before mating and continued with the same diets for a further 14 days after mating. At day 14 of pregnancy the female mice were sacrificed and the placentas and maternal livers were harvested for measurement of the content of thiols and thiobarbituric acid reactive substances (TBARS), as biomarkers of oxidative stress, and the enzymatic activities of total superoxide dismutase (TSOD), copper/zinc SOD (SOD1), manganese SOD (SOD2), selenium glutathione peroxidase (GPX) and glutathione reductase (GR). Diet supplemented with 5% PP improved embryonic survival and reduced embryonic mortality from 28.2% (CONT) to 8.5% (PP5%). This was accompanied by increased activities of placental TSOD, SOD1 and SOD2, and thiol content. Diet supplemented with 5% PP also reduced placental oxidative stress as demonstrated by a decrease of placental TBARS content. This study highlights the potential of interventions with PP-supplemented diet before and during early pregnancy, in order to ameliorate embryonic survival and prevent early pregnancy loss.

Selenium Nutritional Status and Glutathione Peroxidase Activity and Its Relationship with Hemodialysis Time in Individuals Living in a Brazilian Region with Selenium-Rich Soil.

Suboptimal selenium status may impair the antioxidant defense system in patients undergoing hemodialysis, compromising the selenoenzyme glutathione peroxidase activity. To evaluate the association between the duration of hemodialysis, nutritional selenium status, glutathione peroxidase activity (GPx), and thiobarbituric acid reactive substance (TBARS) levels in patients with chronic renal failure undergoing hemodialysis in a region of selenium-rich soils (Ceará, Northeast Brazil). The case-control study of 75 individuals aged 18 to 88 years was allocated between two groups: hemodialysis (n = 41) and control (n = 34). Plasma and erythrocytes selenium levels were determined by inductively coupled plasma optical emission spectrometry. The GPx activity and TBARS levels were also evaluated. In addition, the hemodialysis group was stratified according to the duration of treatment (≤ 59 months and ≥ 60 months). The Mann-Whitney test, Student's t test, and Pearson's or Spearman's correlation were applied according to the data distribution. Moreover, a quantile regression was performed. The significance level (p) was < 0.05. The hemodialysis group had lower selenium levels in their plasma and erythrocytes than the control group (p < 0.001). However, there was no difference in the GPx activity between the groups. Furthermore, an association between the hemodialysis group and selenium levels in plasma (coefficient - 16,343, p < 0.001) and erythrocytes (coefficient - 7839, p = 0.003) was observed by quantile regression, independent of age, sex, and body-mass index. In individuals who had undergone treatment for 60 months or more, GPx activity was lower (p = 0.026) and TBARS levels higher (p = 0.011) than in those who had undergone treatment for less than 60 months. The status of selenium was reduced in the hemodialysis group compared to the control group. The lower GPx activity and higher levels of TBARS in individuals who had undergone treatment for 60 months or more correlated with greater oxidative stress.

The Latest View on the Mechanism of Ferroptosis and Its Research Progress in Spinal Cord Injury.

Ferroptosis is a recently identified nonapoptotic form of cell death whose major markers are iron dependence and accumulation of lipid reactive oxygen species, accompanied by morphological changes such as shrunken mitochondria and increased membrane density. It appears to contribute to the death of tumors, ischemia-reperfusion, acute renal failure, and nervous system diseases, among others. The generative mechanism of ferroptosis includes iron overloading, lipid peroxidation, and downstream execution, while the regulatory mechanism involves the glutathione/glutathione peroxidase 4 pathway, as well as the mevalonate pathway and the transsulfuration pathway. In-depth research has continuously developed and enriched knowledge on the mechanism by which ferroptosis occurs. In recent years, reports of the noninterchangeable role played by selenium in glutathione peroxidase 4 and its function in suppressing ferroptosis and the discovery of ferroptosis suppressor protein 1, identified as a ferroptosis resistance factor parallel to the glutathione peroxidase 4 pathway, have expanded and deepened our understanding of the mechanism by which ferroptosis works. Ferroptosis has been reported in spinal cord injury animal model experiments, and the inhibition of ferroptosis could promote the recovery of neurological function. Here, we review the latest studies on mechanism by which ferroptosis occurs, focusing on the ferroptosis execution and the contents related to selenium and ferroptosis suppressor protein 1. In addition, we summarize the current research status of ferroptosis in spinal cord injury. The aim of this review is to better understand the mechanisms by which ferroptosis occurs and its role in the pathophysiological process of spinal cord injury, so as to provide a new idea and frame of reference for further exploration.

Selenium status and glutathione peroxidase activity in patients with increased susceptibility to cardiometabolic risk: Study of a schizophrenia cohort

Selenium status and glutathione peroxidase activity in patients with increased susceptibility to cardiometabolic risk: Study of a schizophrenia cohort

The possible protective effects of vitamin E and selenium administration in oxidative stress caused by high doses of glucocorticoid administration in the brain of rats

Acute exposure to high doses of glucocorticoids (GCs) may potentially increase the basal levels of reactive oxygen species (ROS) by altering the defence capacity against oxidative damage. Also, antioxidants may affect the oxidative breakdown of tissues. Therefore, the aim of this work was to determine the effects of dietary intake vitamin E and selenium (Se) on lipid peroxidation (LPO) as thiobarbituric acid reactive substances (TBARS) and on the antioxidative defence mechanisms in the brain of rats treated with high doses of prednisolone. Two hundred and fifty adult male Wistar rats were randomly divided into five groups. The rats were fed a normal diet, but groups 3, 4, and 5 received a daily supplement in their drinking water of 20mg vitamin E, 0.3mg Se, and a combination of vitamin E and Se, respectively, for 30days. For 3days subsequently, the control (group 1) was treated with a placebo, and the remaining 4 groups were injected intramuscularly with 100mg/kg body weight (bw) prednisolone. After the last administration of prednisolone, 10 rats from each group were killed at 4, 8, 12, 24, and 48h and the activities of enzymes selenium-glutathione peroxidase (Se-GSH-Px) and catalase (CAT), and the levels of reduced glutathione (reduced GSH) and TBARS in their brains were measured. Se-GSH-Px and CAT enzyme activities, and reduced GSH levels in the prednisolone treatment group (group 2) began to decrease gradually at 4h (p<0.01, p<0.05, respectively), falling respectively to 60, 50, and 40% of the control levels by 24h (p<0.001, p<0.01), and recovering to the control levels at 48h. In contrast, prednisolone administration caused an increase in the brain TBARS, reaching up to six times the level of the control at 24h (p<0.001). However, supplementation with vitamin E and Se had a preventive effect on the elevation of the brain TBARS and improved the diminished activities of antioxidative enzymes and the levels of reduced GSH. Therefore, the present study attempts to determine the sequence of cellular membrane damage in the brain of the rats after high doses GC administration and the possible roles in vivo of vitamin E and Se, and their combination.

Comparative study of the effects of organic selenium on hen performance and productivity of broiler breeders

1. A 10-week experiment was conducted with Ross 308 broiler breeder chickens in cages to evaluate the influence of organic and inorganic sources of selenium (Se) supplementation. A total of 600 birds at 29 weeks of age were divided at random into 4 groups and fed on a maize–soya basal diet supplemented with different forms of Se.2. The first (control) group was given the basal diet without Se supplementation, whereas the second, third and fourth groups were given, respectively, the basal diet with 0.3 mg/kg of inorganic Se in the form of sodium selenite or 0.3 and 0.5 mg/kg of organic Se in the form of Se enriched yeast (Se-yeast).3. The experiment was carried out for 10 weeks to compare and evaluate the influence of Se supplementation on breeder performance, egg production, hatchability and the quality of eggs. Samples were collected for analysis at weeks 0, 5 and 10 of the experimental period.4. At the end of the experiment (39 weeks), there was a reduction in mortality in breeders given diets supplemented with 0.5 mg/kg of Se-yeast. Supplementation of feed with 0.5 mg/kg organic Se increased egg production, percentage of settable eggs and hatchability.5. Selenium supplementation increased egg weight and specific gravity compared to the control diet. However, no significant variation was found in albumen or yolk protein content at the end of week 10.6. Selenium accumulation and glutathione peroxidase (GSHPx) activity were lower in the egg albumen and yolk of control compared with Se-supplemented treatments. Se accumulation and GSHPx activity were higher in the group given 0.3 mg/kg organic compared to 0.3 mg/kg of inorganic Se.7. The results favour the use of Se-yeast at the dose of 0.5 mg/kg in broiler breeder diets for better productivity of eggs, settable eggs, hatchability and higher Se accumulation and antioxidant status in eggs.

Effect of fasting on lipid metabolism and oxidative stability in fattening chicken fed a diet supplemented with organic selenium

Abstract. The aim of the study was to assess the effect of organic selenium dietary supplementation on serum and tissue lipid composition after fattening period and after 48 h fasting in fattening chicken. The study was performed in the Ross hybrid line chicken divided into two groups: control group fed standard diet and Sel Plex group fed standard diet supplemented with 0.3 ppm organic selenium. Blood, liver, intestine and adipose tissue samples were taken upon fattening completion and after 48 h fasting. Total cholesterol, high-density lipoprotein (HDL) cholesterol, low-density lipoprotein (LDL) cholesterol, triacylglycerol and lipoprotein concentrations were determined in serum, whereas total and free cholesterol, triacylglycerol, lipid peroxide and selenium concentrations and glutathione peroxidase activity (GSH-Px) were determined in tissue samples. During fattening period, the correlation of organic selenium with lipid metabolism manifested as decreased concentrations of serum triacylglycerols and very-low-density lipoprotein (VLDL) (P&lt;0.05), liver triacylglycerols (P&lt;0.05), adipose tissue cholesterol (P&lt;0.05) and small intestine cholesterol (P&lt;0.05), and reduced lipid peroxidation (P&lt;0.05). Upon chicken exposure to 48 h fasting, organic selenium supplementation resulted in increased free cholesterol concentration in adipose tissue (P&lt;0.05), GSH-Px activity in the liver (P&lt;0.05), and selenium (P&lt;0.05) accumulation in the liver.

Study of Serum Selenium Level And Its Effect on Male Infertility

Some of the biomedical research has shown interest in the anti-oxidant activity of selenium which could be due to evidences reported that oxidative damage to cells and cell membranes is one of the causative agents in the pathogenesis of many disease states including male infertility. The present study was undertaken with the objective to measure role of Selenium levels in male infertility and assess the effect on different parameters like sperm count, sperm morphology & sperm motility. Our study included 58 infertile and 52 normal fertile males in age group of 22-50 years. The apparent difference in serum Selenium between the normal fertile controls and infertile cases turned out to be statistically significant ( p <0.01) and there seems to be a positive correlation between low serum Selenium levels and semen quality parameters like count, motility and morphology. It is proposed that Selenium acts as free radical scavenger and improves semen quality by virtue of antioxidant component of selenoprotein and classical glutathione peroxidase (GPx) Key words : Infertility Selenium Glutathione peroxidase

Cipura paludosa attenuates long-term behavioral deficits in rats exposed to methylmercury during early development

In the present study, we evaluated the effects of the ethanolic extract (EE) of Cipura paludosa on locomotor, and anxiety- and depression-like behaviors of adult rats exposed to MeHg during early development. Additionally, the antioxidant enzymes catalase (CAT) and selenium-glutathione peroxidase (Se-GPx) were measured in cortical, hippocampal, and cerebellar tissues. Pregnant Wistar rats were treated by gavage with a single dose of MeHg (8mg/kg) on gestational day 15, the developmental stage critical for cortical neuron proliferation. Moreover, prenatal MeHg exposure inhibited CAT and Se-GPx in the cortex and cerebellum. Chronic treatment with the EE of C. paludosa attenuated these emotional and antioxidant deficits induced by prenatal MeHg toxic exposure. This study provides novel evidence that developmental exposure to MeHg can affect not only cognitive functions but also locomotor, and anxiety- and depression-like behaviors .

Filarial selenium glutathione peroxidase: a probable immunodiagnostic marker for lymphatic filariasis

Lymphatic filariasis (LF) caused by Wuchereria bancrofti is widely prevalent in tropical and subtropical countries. Night blood film examination is most commonly used for diagnosis of filariasis but is cumbersome and labour intensive. In order to develop an indirect ELISA-based immunodiagnostic test, the importance of antifilarial IgG subclasses was evaluated in bancroftian filariasis patients. Blood samples from healthy individuals and different categories of LF patients were used to estimate the diagnostic potential of selenium glutathione peroxidase antigen purified from the bovine filarial parasite Setaria cervi. This antigen reacted with both IgG(1) and IgG(4); however, the IgG1 response was greater in microfilaraemic patients and the IgG(4) response was higher in chronic filarial patients. The diagnostic sensitivity of IgG(1) and IgG(4) was 97% and 96% whereas specificity was determined to be 95% and 98% respectively. Our observations suggest that SeGSHPx could be an alternative diagnostic marker for the detection of bancroftian filariasis in an endemic area.

Speciation analysis of selenoproteins in human serum by microbore affinity-HPLC hyphenated to ICP-Sector field-MS using a high efficiency sample introduction system

Microbore affinity-HPLC (AF-HPLC) hyphenated to inductively coupled plasma-sector field mass spectrometry (ICP-SFMS) was applied to the simultaneous speciation analysis of glutathione peroxidase (GPx), selenoprotein P (SelP) and seleno-albumin (SeAlb) in 5 μL of (human) serum. ICP-SFMS (high resolution mode, HR, M/ΔM = 10,000) was used for the quantification of selenium in GPx, SelP and SeAlb after their separation by AF-HPLC, without prior sample preparation or mathematical correction of the spectral interferences. In order to compensate for the loss in sensitivity due to the detection in HR mode and the very low amount of sample taken for analysis, a high-efficiency sample introduction system was used as an interface between AF-HPLC and ICP-SFMS. This led to a signal-to-noise ratio enhancement of about one order of magnitude compared to the conventional experimental ICP-SFMS set-up. Apart from the very low sample consumption, another major advantage of the method described here is the significant reduction of the analysis time (≤7 min). Quantification of GPx, SelP and SeAlb was carried out using on-line (post column) isotope dilution; comparison with on-line external calibration by using Se-L-cystine standard is also addressed. The method accuracy for the determination of total protein bound Se was assessed by the analysis of a human serum reference material (BCR-637) certified for total Se content.

Association between nematode larvae and “low worm egg count diarrhoea” in sheep in Western Australia

Nine flocks of sheep with a high prevalence (>30%) of diarrhoea and severe breech faecal soiling were investigated over a three-year period to examine the causes of diarrhoea in sheep with low mean faecal worm egg counts (WEC). All nine flocks were located in the southwest of Western Australia in areas with a winter rainfall pattern (Mediterranean climate). There was no difference ( p = 0.304) in WEC of diarrhoeic sheep (loose faeces and severe breech faecal soiling) and “normal sheep” (pelleted faeces and mild or no breech faecal soiling). Teladorsagia ( Ostertagia) circumcincta and Trichostrongylus spp. were the nematodes most commonly identified by total worm counts and differentiation of larvae recovered from faeces and pasture. Larval stages of strongyle worms accounted for the largest proportion of total worm counts in both diarrhoeic and normal sheep. Adult worm burdens were small in most sheep. Diarrhoeic sheep had higher numbers of fourth stage larvae than normal sheep ( p = 0.046). There was no histopathological evidence of bacterial or viral causes of diarrhoea in any of the flocks or bacteriological evidence of bacterial infections associated with diarrhoea. Two flocks had marginal selenium glutathione peroxidase (selenium) levels. One flock was diagnosed with helminthosis based on rising WEC and high total worm counts. Larval hypersensitivity diarrhoea, nutritional factors or a combination of these two factors were the most likely causes of diarrhoea in the other eight flocks based on exclusion of other known causes of diarrhoea. Treatment with moxidectin and an ivermectin controlled-release capsule did not change faecal moisture content of treated sheep compared to untreated sheep three to five weeks after treatment. The findings suggest that the immune response to strongyle larvae may explain some cases of low WEC diarrhoea observed during winter–spring in immunocompetent mature sheep grazing in Mediterranean environments.

Dietary incorporation of feedstuffs naturally high in organic selenium for racing pigeons (Columba livia): effects on plasma antioxidant markers after a standardised simulation of a flying effort

Selenium is a trace element of importance for animal health. It is essential for adequate functioning of many enzymes such as, the antioxidant enzyme, glutathione peroxidase, which protects the cell against free radicals. A muscular effort induces a rise in reactive oxygen species production which, in turn, can generate an oxidative stress. Two groups of eight racing pigeons were fed respectively with a diet containing 30.3 (control group) and 195.3 (selenium group) microg selenium/kg diet. The pigeons were submitted to a standardised simulation of a flying effort during 2 h. Blood was taken before and after the effort to measure antioxidant markers and blood parameters related to muscle metabolism. Plasma selenium concentration and glutathione peroxidase activity were significantly higher in the selenium group. There were no significant differences for the other measured parameters. As a consequence of the effort, the pigeons of the selenium group showed a higher increase of glutathione peroxidase activity and a smaller increase of plasma lactate concentration. Variations because of the effort in the other markers were not significantly different between the two groups. It is concluded that the selenium status was improved with the feeding of feedstuffs high in Selenium.

Melatonin decreases the oxidative stress produced by 2,4-dichlorophenoxyacetic acid in rat cerebellar granule cells

2,4-Dichlorophenoxyacetic acid (2,4-D) is one of the most widely used herbicides due to its relatively moderate toxicity and to its biodegradability in the soil. In toxic concentrations, 2,4-D displays strong neurotoxicity, partly due to generation of free radicals. Since melatonin has remarkable antioxidant properties, the objective of this study was to assess to what extent it was effective in preventing the 2,4-D effect on redox balance of rat cerebellar granule cells (CGC) in vitro. Cellular viability, generation of reactive oxygen species (ROS) and reactive nitrogen species (RNS), reduced glutathione (GSH) levels, and the activities of the antioxidant enzymes Cu/Zn-superoxide dismutase (Cu/Zn-SOD), Mn-SOD, selenium-glutathione peroxidase (Se-GPx) and catalase (CAT) were measured in CGC exposed to 2,4-D and/or melatonin for 48 h. In CGC cultures exposed to 2,4-D, cell viability, GSH levels and CAT activity decreased significantly whereas ROS generation and Se-GPx activities were augmented. Except for Se-GPx activity, all these changes were counteracted by the concomitant addition of 0.1 or 0.5 mM melatonin. In addition, incubation of CGC with melatonin alone resulted in augmentation of cell viability, GSH levels and Se-GPx activity. RNS generation and SOD activity remained unaffected by either treatment. Since melatonin was able to counteract most of redox changes produced by 2,4-D in CGC in culture, the experimental evidence reported further support the efficacy of melatonin to act as a neuroprotector.

Evidence for in situ ethanolamine phospholipid adducts with hydroxy-alkenals

Hydroxy-alkenals, such as 4-hydroxy-2(E)-nonenal (4-HNE; from n-6 fatty acids), are degradation products of fatty acid hydroperoxides, including those generated by free radical attack of membrane polyunsaturated fatty acyl moieties. The cytotoxic effects of hydroxy-alkenals are well known and are mainly attributable to their interaction with different molecules to form covalent adducts. Indeed, ethanolamine phospholipids (PEs) can be covalently modified in a cellular system by hydroxy-alkenals, such as 4-HNE, 4-hydroxy-2(E)-hexenal (4-HHE; from n-3 fatty acids), and 4-hydroxy-dodecadienal (4-HDDE; from the 12-lipoxygenase product of arachidonic acid), to form mainly Michael adducts. In this study, we describe the formation of PE Michael adducts in human blood platelets in response to oxidative stress and in retinas of streptozotocin-induced diabetic rats. We have successfully characterized and evaluated, for the first time, PEs coupled with 4-HHE, 4-HNE, and 4-HDDE by gas chromatography-mass spectrometry measurement of their ethanolamine moieties. We also report that aggregation of isolated human blood platelets enriched with PE-4-hydroxy-alkenal Michael adducts was altered. These data suggest that these adducts could be used as specific markers of membrane disorders occurring in pathophysiological states with associated oxidative stress and might affect cell function.

Cysteine supplementation reduces the bioavailability of selenomethionine in mice

Summary Background & aims Selenomethionine, a common form of dietary selenium that is sometimes used to supplement patients with selenium deficiency, must be degraded to an inorganic form of selenium for incorporation into selenium-specific proteins (selenoprotein), and cysteine, which is occasionally added in the total parenteral nutrition preparation, might influence the degradation of selenomethionine. The purpose of this research is to study the influence of cysteine on the metabolism of selenomethionine. Methods An animal study was conducted. Mice were fed a selenomethionine diet with or without cysteine. The control mice were fed a selenite diet. The total selenium concentration and glutathione peroxidase (GPx) activity were measured. Results The mouse experiment showed that the selenium contents in liver, plasma, red blood cells, muscle, and brain were higher in the selenomethionine groups than in the selenite control group. However, the activities of GPx, which were measured in liver, red blood cells, and blood plasma, were lower in the group fed selenomethionine with the addition of cysteine than in the other groups, especially in red blood cells, where the activities were significantly lower than those in mice fed a diet containing only selenomethionine or selenite. Conclusions The results show that the addition of cysteine to a selenomethionine diet may inhibit the selenium metabolism from selenomethionine to selenoproteins, such as extracellular GPx.

Protective effect of Cissus quadrangularis on neutrophil mediated tissue injury induced by aspirin in rats

Cissus quadrangularis (family: Vitaceae) is well known for the treatment of gastric disorders in traditional medicine, owing to its rich source of carotenoids, triterpenoids and ascorbic acid, and has received considerable attention regarding its role in human nutrition. In the search of new potential antiulcer agents, the present study evaluated the ethanol extract of Cissus quadrangularis (CQE) against the gastric toxicity induced by aspirin in rats. The optimum protective dose of 500 mg/kg of extract was selected by the pretreatment of gastric ulcers with different doses of CQE (250, 500 and 750 mg/kg) for 7 days which showed ulcer protection by 40, 71.2 and 72.6%, respectively, as compared to ranitidine (RTD) (30 mg/kg) by 71.9% in the aspirin model. In addition, results have shown that administration of aspirin increases lipid peroxidation status, xanthine oxidase (XO), myeloperoxidase and decrease in selenium–glutathione peroxidase activities in the gastric mucosa, resulting in mucosal damage at both cellular and subcellular level. Pretreatment with CQE ameliorated the observed effect significantly in the gastric mucosa of ulcerated rats. These findings suggest that the gastroprotective activity of CQE could be mediated possibly through its antioxidant effect as well as by the attenuation of the oxidative mechanism and neutrophil infiltration.

Identification and characterization of a selenium-dependent glutathione peroxidase in Setaria cervi

Setaria cervi a bovine filarial parasite secretes selenium glutathione peroxidase during in vitro cultivation. A significant amount of enzyme activity was detected in the somatic extract of different developmental stages of the parasite. Among different stages, microfilariae showed a higher level of selenium glutathione peroxidase activity followed by males then females. However, when the activity was compared in excretory secretory products of these stages males showed higher activity than microfilariae and female worms. The enzyme was purified from female somatic extract using a combination of glutathione agarose and gel filtration chromatography, which migrated as a single band of molecular mass ≈20 kDa. Selenium content of purified enzyme was estimated by atomic absorption spectroscopy and found to be 3.5 ng selenium/μg of protein. Further, inhibition of enzyme activity by potassium cyanide suggested the presence of selenium at the active site of enzyme. This is the first report of identification of selenium glutathione peroxidase from any filarial parasite.

The prooxidant effect of sodium metabisulfite in rat liver and kidney

Sodium metabisulfite (Na 2S 2O 5) is used as an antioxidant and antimicrobial agent in a variety of drugs and functions as a preservative in many food preparations. In addition to their antioxidant activity, sulfites oxidize to sulfite radicals ( SO 3 - ) initiating lipid peroxidation. This study was performed to elucidate the effect of subchronic Na 2S 2O 5 (520 mg/kg/day) ingestion on hepatic and renal antioxidant enzyme activities and lipid peroxidation in albino rats. The antioxidant effect of l-carnitine was also tested in rats treated with Na 2S 2O 5. Plasma uric acid levels were monitored in all rats included in the study. Malondialdehyde (MDA) levels significantly increased in Na 2S 2O 5 treated rats vs. controls, with kidney values of 2.21 ± 0.21 vs. 1.22 ± 0.35 and liver values of 79.85 ± 19.5 vs. 31.36 ± 5.0 nmol/mg protein, respectively. Selenium-glutathione peroxidase (GPx) activity was significantly increased in Na 2S 2O 5 treated rats vs. controls, with kidney values of 38.22 ± 2.21 vs. 8.09 ± 0.76 and liver values of 31.11 ± 6.37 vs. 11.70 ± 1.02 U/g protein, respectively. Sodium metabisulfite treatment increased plasma uric acid levels in rats that were included in the study. No protective effect of l-carnitine was observed against lipid peroxidation in both liver and kidneys of rats treated with Na 2S 2O 5. The presented data confirm the prooxidant activity of sulfites and suggest that increased GPx activity and plasma uric acid levels may partially reduce the observed renal and hepatocellular oxidative damage caused via the ingestion of sulfites.

Cold hardiness in Ostrinia nubilalis (Lepidoptera: Pyralidae): Glycerol content, hexose monophosphate shunt activity, and antioxidative defense system

Many insects in temperate regions overwinter in diapause, during which they are cold hardy. In these insects, one of the metabolic adaptations to the unfavorable environmental conditions is the synthesis of cryoprotectants/anhydroprotectants. The aim of this study was to investigate the connection between the antioxidative system and synthesis of cryoprotectants (mainly glycerol) in diapausing larvae of the European corn borer, Ostrinia nubilalis (Lepidoptera: Pyralidae). At two periods during diapause (November and February), in three groups of insects (kept under field conditions; -12°C for two weeks; 8°C for two weeks), the activity of key enzymes of the antioxidative system and oxidative part of the hexose monophosphate shunt were measured: super- oxide dismutase, catalase, non selenium glutathione peroxidase, glutathione S-transferase, glutathione reductase, glucose 6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase, as well that of the antioxidative components: total glutathione and ascorbate, and dehydroascorbate reductase. There was a higher activity of antioxidative enzymes at the beginning of the dia- pause period (November) compared to late diapause (February), while glutathione and ascorbate were higher in February. Similarly, there was a lower activity of the hexose monophosphate shunt enzymes in February. Exposure of larvae to -12°C resulted in an ele- vation of hexose monophosphate shunt enzyme activity, especially in November. This was accompanied by a significant increase in glycerol content in February. Changes in ascorbate levels and dehydroascorbate reductase activity in both experimental groups (-12°C and 8°C) suggest a connection between the antioxidative system, metabolism during diapause and cold hardiness. Our results support the notion that antioxidative defense in larvae of Ostrinia nubilalis is closely connected with metabolic changes character- istic of diapause, mechanisms of cold hardiness involved in diapause and the maintenance of a stable redox state.