Antioxidant enzyme response to selenium deficiency in rat myocardium

Selenistasis: epistatic effects of selenium on cardiovascular phenotype

Although selenium metabolism is intricately linked to cardiovascular biology and function, and deficiency of selenium is associated with cardiac pathology, utilization of selenium in the prevention and treatment of cardiovascular disease remains an elusive goal. From a reductionist standpoint, the major function of selenium in vivo is antioxidant defense via its incorporation as selenocysteine into enzyme families such as glutathione peroxidases and thioredoxin reductases. In addition, selenium compounds are heterogeneous and have complex metabolic fates resulting in effects that are not entirely dependent on selenoprotein expression. This complex biology of selenium in vivo may underlie the fact that beneficial effects of selenium supplementation demonstrated in preclinical studies using models of oxidant stress-induced cardiovascular dysfunction, such as ischemia-reperfusion injury and myocardial infarction, have not been consistently observed in clinical trials. In fact, recent studies have yielded data that suggest that unselective supplementation of selenium may, indeed, be harmful. Interesting biologic actions of selenium are its simultaneous effects on redox balance and methylation status, a combination that may influence gene expression. These combined actions may explain some of the biphasic effects seen with low and high doses of selenium, the potentially harmful effects seen in normal individuals, and the beneficial effects noted in preclinical studies of disease. Given the complexity of selenium biology, systems biology approaches may be necessary to reach the goal of optimization of selenium status to promote health and prevent disease.

Effect of seabuckthorn (Hippophae rhamnoides ssp. sinensis) leaf extract on the swimming endurance and exhaustive exercise-induced oxidative stress of rats

BACKGROUND

Seabuckthorn (SBT) leaves have significant antioxidant, immunomodulatory and anti-inflammatory properties. The objective of this study was to assess the anti-fatigue, antioxidant and tissue-protective properties of aqueous lyophilised extracts of SBT dried leaves in the hearts of Wistar male rats undergoing exhaustive physical exercise. Doses of 50, 200 and 800 mg kg⁻¹ body weight (BW) day⁻¹ were given orally for 1 week. A week later the rats were forced to swim in barrels until they were exhausted. The times were noted to establish the effective dose of the extracts in rats. After establishing the effective dose, the rats were then sacrificed and assessed for various biochemical parameters.

RESULTS

SBT leaf aqueous extracts (200 and 800 mg kg⁻¹ BW) markedly prolonged the swim time of rats. Supplementation with SBT leaf aqueous extracts helped reduce the exhaustive exercise-induced increase in malondialdehyde level and selenium-dependent glutathione peroxidase activity. Alanine aminotransferase and creatine kinase levels were lowered in the exhaustive exercise with SBT treatment group (E + SBT) compared with the exhaustive exercise group (E).

CONCLUSION

The findings suggest that SBT leaf aqueous extract supplements can enhance exercise capacity and protect against oxidative damage caused by exhaustive exercise in rats.

Effect of selenium supplementation on lipid peroxidation, antioxidant enzymes, and lactate levels in rats immediately after acute swimming exercise

The present study aims to evaluate the effect of selenium supplementation on lipid peroxidation and lactate levels in rats subjected to acute swimming exercise. Thirty-two adult male rats of Sprague-Dawley type were divided into four groups. Group 1, control; group 2, selenium-supplemented; group 3, swimming control; group 4, selenium-supplemented swimming group. The animals in groups 2 and 4 were supplemented with (i.p.) 6 mg/kg/day sodium selenite for 4 weeks. The blood samples taken from the animals by decapitation method were analyzed in terms of erythrocyte-reduced glutathione (GSH), serum glutathione peroxidase (GPx) and superoxide dismutase (SOD), and plasma malondialdehyde (MDA) and lactate using the colorimetric method, and serum selenium values using an atomic emission device. In the study, the highest MDA and lactate values were found in group 3, while the highest GSH, GPx and SOD values were obtained in group 4 (p < 0,001). Group 2 had the highest and group 3 had the lowest selenium levels (p < 0,001). Results of the study indicate that the increase in free radical production and lactate levels due to acute swimming exercise in rats might be offset by selenium supplementation. Selenium supplementation may be important in that it supports the antioxidant system in physical activity.

Cardioprotective effects of nitrite during exercise

Exercise training has been shown to reduce many risk factors related to cardiovascular disease, including high blood pressure, high cholesterol, obesity, and insulin resistance. More importantly, exercise training has been consistently shown to confer sustainable protection against myocardial infarction in animal models and has been associated with improved survival following a heart attack in humans. It is still unclear how exercise training is able to protect the heart, but some studies have suggested that it increases a number of classical signalling molecules. For instance, exercise can increase components of the endogenous antioxidant defences (i.e. superoxide dismutase and catalase), increase the expression of heat shock proteins, activate ATP-sensitive potassium (K(ATP)) channels, and increase the expression and activity of endothelial nitric oxide (NO) synthase resulting in an increase in NO levels. This review article will provide a brief summary of the role that these signalling molecules play in mediating the cardioprotective effects of exercise. In particular, it will highlight the role that NO plays and introduce the idea that the stable NO metabolite, nitrite, may play a major role in mediating these cardioprotective effects.

Whole blood selenium concentrations in endurance horses

Exercise causes an increase in the production of reactive oxygen species, which can result in oxidant/antioxidant disequilibrium. Deficiency of antioxidants can further alter this balance in favor of pro-oxidation. Selenium (Se) is one of many antioxidant catalysts, as a component of the glutathione peroxidase enzymes. Soils and forages vary widely in Se concentration and a deficient diet can lead to sub-clinical or clinical deficiency in horses. Endurance horses are prone to oxidative stress during long periods of aerobic exercise and their performance could be affected by Se status. This study investigated the blood Se concentration in a group of endurance horses (n=56) residing and competing in California, a state containing several regions that tend to produce Se-deficient forages. The rate of Se deficiency in this group of horses was low, with only one horse being slightly below the reference range. Higher blood Se concentrations were not associated with improved performance in terms of ride time. There was no significant difference in Se concentration between horses that completed the ride and those that were disqualified, although blood Se concentrations were significantly higher in horses that received oral Se supplementation. An increase in blood Se concentration was observed following exercise and this warrants further study.

Effects of endurance training and acute exhaustive exercise on antioxidant defense mechanisms in rat heart

We investigated whether 8-week treadmill training strengthens antioxidant enzymes and decreases lipid peroxidation in rat heart. The effects of acute exhaustive exercise were also investigated. Male rats (Rattus norvegicus, Sprague-Dawley strain) were divided into trained and untrained groups. Both groups were further divided equally into two groups where the rats were studied at rest and immediately after exhaustive exercise. Endurance training consisted of treadmill running 1.5 h day(-1), 5 days week(-1) for 8 weeks. For acute exhaustive exercise, graded treadmill running was conducted. Malondialdehyde level in heart tissue was not affected by acute exhaustive exercise in untrained and trained rats. The activities of glutathione peroxidase and glutathione reductase enzymes decreased by both acute exercise and training. Glutathione S-transferase and catalase activities were not affected. Total and non-enzymatic superoxide scavenger activities were not affected either. Superoxide dismutase activity decreased by acute exercise in untrained rats; however, this decrease was not observed in trained rats. Our results suggested that rat heart has sufficient antioxidant enzyme capacity to cope with exercise-induced oxidative stress, and adaptive changes in antioxidant enzymes due to endurance training are limited.

Effects of baseline serum levels of Se on markers of eccentric exercise-induced muscle injury

Inflammation and oxidative stress have been implicated in the mechanism of eccentric exercise-induced muscle injury. This study examined whether baseline serum levels of selenium (Se), a trace element that participates in both antioxidant and anti-inflammatory systems, affects the overall response to injury. Thirteen males performed 36 maximal eccentric actions with the elbow flexors of the non-dominant arm on a motorized dynamometer. Venous blood samples were collected immediately before and after exercise at 2, 24, 48, 72 and 96 hours. Established indicators of muscle damage such as maximum isometric torque (MIT), range of motion (ROM), relaxed arm angle (RANG), flexed arm angle (FANG), arm circumference (CIRC), muscle soreness and serum levels of creatine kinase (CK) and lactate dehydrogenase (LDH) were determined at the same time points. Baseline serum levels of Se were also measured. Complementary data regarding assessment of Se status were retrieved by the use of a semi-quantitative food frequency questionnaire. All measures changed significantly (p<0.05) after exercise. The main finding of this study was that baseline Se serum levels were associated inversely with CK, LDH and FANG and positively with MIT and ROM (p<0.05). These data suggest that beyond overt Se deficiency, suboptimal Se status possibly worsens muscle functional decrements subsequent to eccentric muscle contractions.

Selenoproteins, Cholesterol-Lowering Drugs, and the Consequences Revisiting of the Mevalonate Pathway

3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors (statins) and peroxisome proliferator-activated receptor alpha activators (fibrates) are the backbone of pharmacologic hypercholesterolemia and dyslipidemia treatment. Many of their clinical effects, however, are still enigmatic. This article describes how a side road of the mevalonate pathway, characterized in recent years, can rationalize a major fraction of these unexplained observations. This side road is the enzymatic isopentenylation of selenocysteine-tRNA([Ser]Sec) (Sec-tRNA), the singular tRNA to decode the unusual amino acid selenocysteine. The functionally indispensable isopentenylation of Sec-tRNA requires a unique intermediate from the mevalonate pathway, isopentenyl pyrophosphate, which concomitantly constitutes the central building block for cholesterol biosynthesis, and whose formation is suppressed by statins and fibrates. The resultant inhibition of Sec-tRNA isopentenylation profoundly decreases selenoprotein expression. This effect might seamlessly explain the immunosuppressive, redox, endothelial, sympatholytic, and thyroidal effects of statins and fibrates as well as their common side effects and drug interactions.

Profiles of enzymatic activity in earthworms from zinc, lead and cadmium polluted areas near Olkusz (Poland)

The aim of the study was to determine whether there are signs of adaptation of soil fauna to a gradient of heavy metal contamination. Earthworms Aporrectodea caliginosa, Lumbricus terrestris and Eisenia fetida were collected during the spring and summer of 2000 and 2001 from meadow sites situated between 2 and 32 km from the Bukowno-Olkusz complex of zinc-lead ore mines and smelters. The heavy metal content in the soil near smelters reaches 10,500 mg/kg (d.w.) for Zn, 2600 mg/kg for Pb and 81.9 mg/kg for Cd. The sites differ with respect to species composition of earthworm community, with A. caliginosa being dominant. Complete data was obtained only for A. caliginosa, since other species were not abundant at all investigated sites during the whole period of investigation. The body burdens of Zn, Pb, Cd and Cu in A. caliginosa reached 1500, 100, 220 and 10 microg/g, respectively, in the vicinity of the smelter (2-4 km), and decreased to 400, 2, 36 and 6 microg/g at the most distant site (32 km). Cadmium and lead content was significantly elevated in the whole body of L. terrestris collected at the site 2.5 km distant from the smelters when compared to more distant sites, while in E. fetida only the body burden of cadmium was elevated at the nearest site compared to the next site of transect. Activities of glutathione peroxidase (GPX; EC 1.11.1.9) against hydrogen peroxide (H2O2) or cumene hydroperoxide (cumOOH), glutathione reductase (GR; EC 1.6.4.2), glutathione S-transferase (GST; EC 2.5.1.18) and catalase (CAT; EC 1.11.1.6) were assayed in postmitochondrial supernatant obtained from whole body homogenates. Seasonal and annual variations of enzyme activity were reflected by higher GPX activity in the late summer of 2001 in comparison with the spring and summer of 2000. This may reflect severe drought in the spring and summer of 2000. The activity of both GPX isozymes, GR and GST in A. caliginosa and L. terrestris increased with increasing distance from the smelters and reached maximum at sites III and IV (4 and 8 km from the smelters, respectively) and then it decreased in the animals from site V (32 km). These may be the effects of antagonism between the enzyme inducing and enzyme inhibiting action of smelter emissions, a phenomenon known as a hormetic effect. It is postulated here that this effect is of diagnostic value for metal pollution biomonitoring.

Exercise training preserves coronary flow and reduces infarct size after ischemia-reperfusion in rat heart

The effect of endurance training on the resistance of the heart to left ventricular (LV) functional deficit and infarction after a transient regional ischemia and subsequent reperfusion was examined. Female Sprague-Dawley rats were randomly assigned to an endurance exercise training (Tr) group or a sedentary (Sed) control group. After 20 wk of training, hearts were excised, perfused, and instrumented for assessment of LV mechanical function, and the left anterior descending coronary artery was occluded to induce a transient regional ischemia (1 h) that was followed by 2 h of reperfusion. Throughout much of the regional ischemia-reperfusion protocol, coronary flow rates, diastolic function, and LV developed pressure were better preserved in hearts from Tr animals. During the regional ischemia, coronary flow to myocardium outside the ischemic zone at risk (ZAR) was maintained in Tr hearts, whereas it progressively fell in Sed hearts. On release of the coronary artery ligature, flow to the ZAR was greater in Tr than in Sed hearts. Infarct size, expressed as a percentage of the ischemic ZAR, was significantly smaller in hearts from Tr rats (24 +/- 3 vs. 32 +/- 2% of ZAR, P < 0.05). Mn- and CuZn-SOD protein expression were higher in the LV myocardium of Tr animals (P < 0.05 for both isoforms). Our data indicate that long-term exercise training leads to infarct sparing and better maintenance of coronary flow and mechanical function after ischemia-reperfusion.

Skeletal muscle disorders associated with selenium deficiency in humans

Skeletal muscle disorders manifested by muscle pain, fatigue, proximal weakness, and serum creatine kinase (CK) elevation have been reported in patients with selenium deficiency. The object of this report was to review the conditions in which selenium deficiency is associated with human skeletal muscle disorders and to evaluate the importance of mitochondrial alterations in these disorders. A systematic literature review using the Medline database and Cochrane Library provided 38 relevant articles. The main conditions associated with selenium deficiency fell into three categories: (1) insufficient selenium intake in low soil-selenium areas; (2) parenteral or enteral nutrition, or malabsorption; and (3) chronic conditions associated with oxidative stress, such as chronic alcohol abuse and human immunodeficiency virus (HIV) infection. In low soil-selenium areas, reversibility of muscle symptoms was similar after selenium supplementation and placebo administration, suggesting a role for other factors in the development of disease. In parenteral or enteral nutrition, or malabsorption, muscle symptoms improved after selenium supplementation in 18 of 19 patients (median delay: 4 weeks). The reason that only a minority of selenium-deficient patients present with skeletal muscle disorders is unclear and is possibly related to cofactors, such as viral infections and drugs. Prospective studies of selenium-deficient myopathies would be useful in critically ill patients, alcohol abusers, and HIV-infected patients.

Glutathione deficiency intensifies ischaemia-reperfusion induced cardiac dysfunction and oxidative stress

The efficacy of glutathione (GSH) in protecting ischaemia-reperfusion (I-R) induced cardiac dysfunction and myocardial oxidative stress was studied in open-chest, stunned rat heart model. Female Sprague-Dawley rats were randomly divided into three experimental groups: (1) GSH-depletion, by injection of buthionine sulphoxamine (BSO, 4 mmol kg(-1), i.p.) 24 h prior to I-R, (2) BSO injection (4 mmol kg(-1), i.p.) in conjunction with acivicin (AT125, 0.05 mmol kg(-1), i.v.) infusion 1 h prior to I-R, and (3) control (C), receiving saline treatment. Each group was further divided into I-R, with surgical occlusion of the main left coronary artery (LCA) for 30 min followed by 20 min reperfusion, and sham. Myocardial GSH content and GSH : glutathione disulphide (GSSG) ratio were decreased by approximately 50% (P < 0.01) in both BSO and BSO + AT125 vs. C. Ischaemia-reperfusion suppressed GSH in both left and right ventricles of C (P < 0.01) and left ventricles of BSO and BSO + AT125 (P < 0.05). Contractility (+dP/dt and -dP/dt) in C heart decreased 55% (P < 0.01) after I and recovered 90% after I-R, whereas +/-dP/dt in BSO decreased 57% (P < 0.01) with ischaemia and recovered 76 and 84% (P < 0.05), respectively, after I-R. For BSO + AT125, +/-dP/dt were 64 and 76% (P < 0.01) lower after ischaemia, and recovered only 67 and 61% (P < 0.01) after I-R. Left ventricular systolic pressure in C, BSO and BSO + AT125 reached 95 (P > 0.05) 87 and 82% (P < 0.05) of their respective sham values after I-R. Rate-pressure double product was 11% (P > 0.05) and 25% (P < 0.05) lower in BSO and BSO + AT125, compared with Saline, respectively. BSO and BSO + AT125 rats demonstrated significantly lower liver GSH and heart Mn superoxide dismutase activity than C rats after I-R. These data indicate that GSH depletion by inhibition of its synthesis and transport can exacerbate cardiac dysfunction inflicted by in vivo I-R. Part of the aetiology may involve impaired myocardial antioxidant defenses and whole-body GSH homeostasis.

Protective effect of vitamin E, beta-carotene and N-acetylcysteine from the brain oxidative stress induced in rats by lipopolysaccharide

The major goal of this study was to examine the ability of several antioxidants namely, vitamin E, beta-carotene and N-acetylcysteine, to protect the brain from oxidative stress induced by lipopolysaccharide (LPS, endotoxin). LPS, a component of the bacterial wall of gram-negative bacteria, has been recognized as one of the most potent bacterial products in the induction of host inflammatory responses and tissue injury and was used in this study to mimic infections. LPS injection resulted in a significant increase in the stress indices, plasma corticosterone and glucose concentration, a significant alteration of the brain oxidative status observed as elevation of the level of malondialdehyde (MDA, index of lipid peroxidation) and reduction of reduced glutathione (GSH), and a disturbance in the brain energy metabolism presented as a reduction in the ATP/ADP ratio and an increase in the mitochondrial/cytosolic hexokinase ratio. However, the activities of brain superoxide dismutase and Na+, K+-ATPase and contents of cholesterol and phospholipids were not altered. Administration of the aforementioned antioxidants prior to LPS injection ameliorated the oxidative stress by reducing levels of MDA, restoring GSH content and normalizing the mitochondrial/cytosolic hexokinase ratio in the brain in addition to lowering levels of plasma corticosterone and glucose. In conclusion, this study showed the increased free radical generation during infections and LPS-induced stress. It also suggests that brain oxidative status and energy is disturbed.

Contents and uptake rates of Mn, Fe, Co, Zn, and Se in Se-deficient rat liver cell fractions

The contents of manganese (Mn), iron (Fe), cobalt (Co), zinc (Zn), and selenium (Se) in nuclear (NU), mitochondrial (MT), microsomal (MC), and cytosolic (CS) fractions of liver homogenates of normal and selenium-deficient (SeD) rats were determined by instrumental neutron activation analysis (INAA). The uptake rates of these elements in the liver cell fractions of both groups of rats were determined by multitracer analysis (MTA). The results indicated that Se-deficiency caused a significant increase in the content of Fe in the MC fractions. The MTA showed that the uptake rate of Fe was highest in the MC fraction, and that the uptake rate in the fraction was similar between the SeD and normal rats.

Effects of selenium deficiency on the response of cardiac tissue to ischemia and reperfusion

Over a 10-week period, female Wistar rats received a diet containing a low level of selenium, cofactor of the antioxidant enzyme glutathione peroxidase (GPx) in order to examine the influence of deficiency of this trace element (i) on tissue antioxidant enzyme defence systems, and (ii) on the susceptibility of the myocardium to ischemia-reperfusion injury. At the end of the dietary treatment, hearts were perfused at constant flow (11 ml/min) before being subjected to 15 min of global normothermic ischemia, followed by 30 min of reperfusion. The effects of selenium deficiency were estimated by studying functional recovery of various cardiac parameters (left ventricular developed pressure LVDevP, heart rate HR, and the product HR x LVDevP), as well as ultrastructural tissue characteristics. Furthermore, superoxide dismutase (SOD) and glutathione peroxidase (GPx) activities were measured at the end of the reperfusion period. Results suggest that: (a) the activity of GPx is decreased by selenium deficiency while SOD activity remains unchanged, (b) the recovery of cardiac function and myocardial ventricular ultrastructure during reperfusion are altered in the selenium-deficient group compared to controls. These results illustrate the crucial role that selenium, the co-factor of one of the major antioxidant enzymes of the myocardium, plays in determining the vulnerability of the heart to ischemia and reperfusion.

Myocardial diastolic function and exercise

There are several important links between aerobic exercise performance and the diastolic phase of the cardiac cycle. During acute exercise, diastolic function must be augmented in order for left ventricular filling to match increased left ventricular output, i.e., cardiac output. This challenges the myocardium because the shortened duration of diastole during exercise may compromise left ventricular filling, thereby limiting the stroke volume. Additionally, left ventricular filling must be accomplished at relatively low filling pressures, otherwise pulmonary vascular congestion may occur. Left ventricular diastolic function may be impaired in the elderly and/or in individuals with ischemic coronary syndromes. Regular aerobic exercise training appears to enhance left ventricular diastolic function and may benefit patients with clinically relevant "diastolic dysfunction." The purpose of this paper is to discuss the relative importance between diastole and exercise and to review some of the involved putative mechanisms.

Exercise training-induced alterations in skeletal muscle antioxidant capacity: a brief review

Cellular oxidants include a variety of reactive oxygen, nitrogen, and chlorinating species. It is well established that the increase in metabolic rate in skeletal muscle during contractile activity results in an increased production of oxidants. Failure to remove these oxidants during exercise can result in significant oxidative damage of cellular biomolecules. Fortunately, regular endurance exercise results in adaptations in the skeletal muscle antioxidant capacity, which protects myocytes against the deleterious effects of oxidants and prevents extensive cellular damage. This review discusses the effects of chronic exercise on the up-regulation of both antioxidant enzymes and the glutathione antioxidant defense system. Primary antioxidant enzymes superoxide dismutase, glutathione peroxidase, and catalase will be discussed as well as glutathione, which is an important nonenzymatic antioxidant. Growing evidence indicates that exercise training results in an elevation in the activities of both superoxide dismutase and glutathione peroxidase along with increased cellular concentrations of glutathione in skeletal muscles. It seems plausible that increased cellular concentrations of these antioxidants will reduce the risk of cellular injury, improve performance, and delay muscle fatigue.

Effect of antioxidant trace elements on the response of cardiac tissue to oxidative stress

It is now well established that several trace elements, because of their involvement in the catalytic activity and spatial conformation of antioxidant enzymes, may contribute to the prevention of oxidative stress such as occurs upon reperfusion of ischemic tissue. The aim of this paper is (1) to review the role of these trace elements (Cu, Mn, Se, and Zn) in antioxidant cellular defenses in the course of post-ischemic reperfusion of cardiac tissue, (2) to provide experimental data suggesting that variations in trace element dietary intake may modulate the vulnerability of cardiac tissue to ischemia-reperfusion, and (3) to discuss in more detail the effect of Mn ions, which seem to play a special protective role against reperfusion injury. Some results obtained from experiments in animal models of myocardial reperfusion have shown that the dietary intake of such trace elements can modulate cardiac activity of antioxidant enzymes and, consequently, the degree of reperfusion damage. In addition, experimental data on the protective effects of an acute treatment with Mn are presented. Finally, experimental evidence on the protective role of salen-Mn complexes, which exhibit catalytic SOD- and CAT-like activities against reperfusion injury, are described. These complexes should be of considerable interest in clinical conditions.

Influence of selenium deficiency on vital functions in rats

To clarify the relationship between selenium (Se) deficiency and functional disorders, the authors determined the Se concentration, anti-oxidant enzyme activity, and other parameters in rats fed a Se-deficient diet. Rats fed the Se-deficient diet showed a decrease in Se concentration and glutathione peroxidase (GSH-Px) activity in plasma, erythrocytes, heart, liver, and skeletal muscle from the first week after the initiation of the diet, an increase in heart lipid peroxide concentration from the second week, and an increase in liver glutathione S-transferase activity from the fourth week. From the twelfth week, a decrease in the growth rate in the rats fed the Se-deficient diet was observed. In spite of this growth impairment, no changes in electrocardiogram, muscle tone, degree of hemolysis, plasma biochemistry, or hematological values were detected. In summary, the authors found that a reduction of body Se is easily induced, but that the appearance of functional disorders following Se deficiency is difficult to detect in rats.

Effect of dietary antioxidant trace element supply on cardiac tolerance to ischemia-reperfusion in the rat

Over a 10-week period, female Wistar rats received a diet containing various levels of four trace elements (Zn, Cu, Mn, Se), co-factors of antioxidant enzymes (superoxide dismutase SOD, glutathione peroxidase GPx), in order to examine the influence of supplementation or deficiency of these elements (i) on tissue antioxidant enzyme defence systems, and (ii) on the susceptibility of the myocardium to ischemia-reperfusion injury. At the end of the dietary treatment, hearts were perfused at constant flow (11 ml/min) before being subjected to 15 min of total global normothermic ischemia, followed by reperfusion. The effects of the various diets (deficient, standard or supplemented) were estimated by studying functional recovery of various cardiac parameters (left ventricular developed pressure LVDP, dP/dtmax, heart rate x LVDP) as well as ultrastructural tissue characteristics. Furthermore, SOD and GPx activities were measured before ischemia and at the end of the reperfusion period. Results suggest that: (a) the activity of antioxidant enzymes increased or decreased significantly when diet was respectively supplemented with, or deficient in, trace elements, but was not further modified by an ischemia-reperfusion episode: (b) the recovery of cardiac function during reperfusion, and ventricular myocardial ultrastructure were significantly improved under the influence of trace element supplementation when compared to both standard and deficient groups. These results illustrate the protective effect of trace elements which are co-factors of antioxidant enzymes in limiting ischemia-reperfusion induced injury, and suggest a possible use in the field of anti-ischemic therapy.

Oxidative stress during exercise: implication of antioxidant nutrients

Research evidence has accumulated in the past decade that strenuous aerobic exercise is associated with oxidative stress and tissue damage in the body. There is indication that generation of oxygen free radicals and other reactive oxygen species may be the underlying mechanism for exercise-induced oxidative damage, but a causal relationship remains to be established. Enzymatic and nonenzymatic antioxidants play a vital role in protecting tissues from excessive oxidative damage during exercise. Depletion of each of the antioxidant systems increases the vulnerability of various tissues and cellular components to reactive oxygen species. Because acute strenuous exercise and chronic exercise training increase the consumption of various antioxidants, it is conceivable that dietary supplementation of specific antioxidants would be beneficial.