Influence of dietary peroxides, selenium and vitamin E on glutathione peroxidase of the gastrointestinal tract.

The influence of dietary peroxides, vitamin E and selenium on glutathione peroxidase (GSH-Px) activity in the gastrointestinal tract of the rat was investigated. Feeding 7% oxidized stripped corn oid (peroxide value 1,000) in a diet adequate in selenium and vitamin E increased the specific activity of GSH-Px in the stomach mucosa. Feeding oxidized oil produced an increase in the wet weight of the intestinal mucosa which was associated with a decrease in the specific activity of the enzyme. Total GSH-Px activity in the intestinal mucosa was unchanged or moderately increased. These changes were unaffected by the presence of vitamin E in the diet. Dietary peroxides had no effect on GSH-Px activity in the plasma or in the perirenal and paraepididymal adipose tissues. Subacute vitamin E deficiency had no consistent effect on the activity of the enzyme in several tissues examined. In rats fed a Se deficient diet glutathione peroxidase activity decreased markedly in most tissues but only slightly in the intestinal mucosa. The moderate decrease in the intestine may be explained by the accessibility of residual dietary Se to the mucosal cells. The role of Se in the detoxification of peroxides in foods and the response of gastrointestinal GSH-Px to dietary peroxides are discussed.     

Effect of selenite, vitamin E and N,N'-diphenyl-p-phenylenediamine on liver organic solvent-soluble lipofuscin pigments in mice

The present experiment was designed to investigate the effect of selenium (Se) supplementation, as sodium selenite, on organic solvent-soluble lipofuscin pigment (OLP) accumulation and glutathione peroxidase (GSH-Px) activity in the livers of mice fed varying levels of vitamin E or N,N'-diphenyl-p-phenylenediamine (DPPD). Four groups of 16 female, weanling mice each were fed either a vitamin E-deficient diet, a diet supplemented with 30 mg/kg or 300 mg/kg vitamin E (as RRR-alpha-tocopheryl acetate), or a diet supplemented with 30 mg/kg DPPD. Each diet contained 0.05 ppm Se. At 5 months of age, eight animals from each dietary group were supplemented with an additional 0.1 ppm Se, as sodium selenite, in their drinking water. The remaining animals were fed their original diets through the 9-month experimental period. Selenite supplementation resulted in a significant increase in OLP concentration and GSH-Px activity in the liver of mice fed vitamin E- or DPPD-supplemented diets. Normal levels of vitamin E and DPPD (30 mg/kg) were not sufficient to protect against the oxidative effects of selenite; however, 10 times the normal level of vitamin E (300 mg/kg) markedly suppressed this oxidative effect.     

Dietary selenium requirement of fingerling channel catfish

Two experiments were conducted in aquaria to determine the minimum dietary selenium requirement of fingerling channel catfish (Ictalurus punctatus). Casein-gelatin diets containing graded levels of supplemental selenium (as Na2SeO3) ranging from 0 to 15 mg/kg were fed to catfish for 15 weeks in experiment 1 to broadly define their selenium requirement and toxicity levels. Although growth of catfish was affected by dietary selenium level, significant differences in weight gain were not easily discernible due to variability among the groups of fish. Weight gain data generally indicated that the basal diet containing 0.06 mg Se/kg diet caused growth depression, and a supplemental selenium level of 15 mg/kg also caused a reduced growth response, which indicated selenium toxicity. Selenium concentrations in edible muscle tissue increased almost linearly with increasing dietary selenium levels. Liver and plasma selenium-dependent glutathione peroxidase (Se GSH-Px) activities indicated the selenium requirement of fingerling channel catfish was between 0.1 and 0.5 mg Se/kg diet. In experiment 2, casein-gelatin diets containing incremental levels of supplemental selenium were fed to catfish for 14 weeks to more precisely determine their minimum dietary selenium requirement. Growth data and liver and plasma Se GSH-Px activities indicated that the minimum selenium requirement of fingerling channel catfish fed adequate vitamin E was 0.25 mg Se/kg dry diet. Based on these data, it appears that selenium supplementation of commercial catfish feeds is warranted.     

Evidence for increased selenium requirement for the rat during pregnancy and lactation

Adequacy of the National Research Council (NRC) selenium (Se) requirement for growth (0.1 ppm Se) was assessed in reproducing Sprague-Dawley rats. Either a casein-based diet with no added Se or the same diet supplemented with selenite to contain 0.05, 0.1, or 0.2 ppm Se was fed during pregnancy and lactation and to nonreproducing controls. Only 0.05 ppm Se was necessary to maintain maximal red blood cell (RBC) and liver Se concentrations and glutathione peroxidase (GSH-Px) activities in controls, whereas 0.2 ppm Se was necessary to maintain comparable RBC Se during pregnancy and tissue Se and GSH-Px activities during lactation. On d 2 of lactation, no differences in pup tissue Se or GSH-Px activities could consistently be related to maternal Se intake. By d 18 of lactation, however, Se status of nursing pups reflected maternal Se intake. Pups of dams fed 0.2 ppm Se had tissue Se and GSH-PX activities significantly greater than those of all other pups. Milk Se content correlated significantly with maternal Se intake and plasma Se and with pup tissue Se and GSH-Px activities. These results indicate that during reproduction 0.1 ppm Se is not adequate to maintain maternal tissue Se or GSH-Px activities comparable to those of normal controls; 0.2 ppm dietary Se is more appropriate, resulting in maternal GSH-PX activities similar to those of controls fed 0.1 ppm Se and milk Se concentrations that result in greater pup tissue GSH-Px activities.     

Selenium, vitamin E and the response to swimming stress in the rat.

Experiments were conducted to determine the effects of exercise on rat glutathione peroxidase system enzymes and lipid peroxidation among animals supplemented and unsupplemented with selenium (Se) and vitamin E (E). Liver, muscle and blood were taken before, immediately after and 24 hours after exercising to exhaustion by swimming. No effect of exercise was found on muscle or liver enzymes, although exercise resulted in depressed glutathione reductase (GR) and glucose-6-phosphate dehydrogenase (G6PD) activities in erythrocytes immediately after exercise. Dietary Se supplementation did result in increased hepatic muscle and erythrocyte glutathione peroxidase activity, and decreased hepatic GR, G6PD and "malic enzyme" activities. Thiobarbituric acid reactive substances, and indicator of lipid peroxidation, increased in liver and muscle subsequent to exercise. This increase was reduced in liver, but not eliminated, by dietary E supplementation. The increase was not affected by dietary E in muscle, nor by dietary Se in either tissue.     

膳食维生素B_6对硒的生物利用率影响的研究 Ⅱ．对大鼠组织谷胱甘肽过氧化物酶活性的影响

实验用４周龄断乳雄性大鼠观察膳食维生素Ｂ６（ＶＢ６）对饲亚硒酸钠（ＳｅＬ）或ＤＬ－硒蛋氨酸（ＳｅＭｅｔ）大鼠组织中ＧＳＨ－Ｐｘ活性的影响，实验期为４周。实验证明：与补ＶＢ６各组相比，缺ＶＢ６各组血浆ＧＳＨ－Ｐｘ活性较高，而在红细胞中的结果相反（Ｐ＜０．０５）；缺ＶＢ６各组动物的骨骼肌、心肌和脾脏中ＧＳＨ－Ｐｘ活性都显著低于补Ｂ６各组（Ｐ＜０．０５），上述结果与给硒的化学形式无关。在用ＳｅＭｅｔ的处理组，缺Ｂ６大鼠的肝脏中ＧＳＨ－Ｐｘ活性显著低于补ＶＢ６的大鼠；而在用ＳｅＬ的处理组则没有观察到ＶＢ６的这种影响。本研究结果提示，硒掺入ＧＳＨ－Ｐｘ是通过一个ＶＢ６依存的过程。     

Subnormal concentrations of serum selenium and plasma carnitine in chronically tube-fed patients

Forty-seven tube-fed nursing home patients were investigated with regard to serum or plasma selenium (Se), carnitine, and red blood cell (RBC) glutathione peroxidase (GSH-Px). Thirty-six patients were tube fed with Isocal, and 11 were tube fed with Compleat B, an L-carnitine-containing formula. Eighteen elderly nursing home patients and 10 young adults served as controls. Serum Se and plasma carnitine were lowest (p less than 0.05) in the Isocal patients. In all 36 Isocal subjects, Se was below normal, and in 26% of Isocal patients RBC GSH-Px was also below normal. Free and total carnitine were below normal in most Isocal subjects. All 11 Compleat B patients had subnormal serum Se, but most had normal carnitine concentrations. These data suggest that enteral formulae in nursing homes should contain greater than 100 micrograms Se and on the order of a mmol carnitine/1600 kcal.     

The necessity of dietary vitamin B6 to selenium biopotency for tissue selenium and glutathione peroxidase in rats.

Necessity of dietary vitamin B6 to the biopotency of selenium (Se) for the levels of Se and glutathione peroxidase (GSH-Px) in tissues was investigated. Male Wistar 12-week-old rats were fed a vitamin B6-Se-deficient basal diet for 3 weeks, and then the rats were divided into 6 groups. One group was fed the basal diet, the others were fed the diet supplemented with 250 micrograms vitamin B6/100 g as pyridoxine.HCl, or 0.25 mg Se/kg as Na2SeO3 (SeL) or DL-selenomethionine (Se-Met), or both (SeL+B6 or Se-Met+B6) for 10 week. The levels of Se and GSH-Px in erythrocytes and muscle were significantly higher in vitamin B6-supplemented groups than in vitamin B6-deficient groups. There was little effect of this vitamin deficiency on Se level in liver of rats fed SeL; however, a higher Se level in liver was observed in vitamin B6-deficient rats fed Se-Met than in the corresponding B6-supplemented rats. A significant decrease of GSH-Px activity in liver was found in vitamin B6-deficient animals fed Se-Met compared with vitamin B6-supplemented animals, whereas no significant decrease was observed in those fed SeL. These results suggest that this vitamin is involved in the transport and deliverance of Se in plasma to the other tissues and the incorporation of Se from Se-Met to GSH-Px in liver.     

Effects of feeding selenium deficient diets to rhesus monkeys (Macaca Mulatta).

Pregnant rhesus monkeys (Macaca mulatta) were fed either selenium (Se) deficient or Se supplemented diets with adequate vitamin E. Except for some cardiac irregularities in the first babies born to these females, no physiological disorders due to Se deficiency were seen in a subsequent offspring. Plasma and erythrocyte glutathione peroxidase activities and blood Se levels increased in the Se supplemented monkeys but decreased in the deficient ones. The data indicated that hair Se levels reflect long term exposure to this element. In a very preliminary experiment, evidence was obtained to indicate that dietary protein deficiency along with Se deficiency will generate cardiomyopathic lesions characteristic of Se deficiency. It is hypothesized that, in addition to Se deficiency, another dietary deficiency (or abnormality) is necessary to produce Se deficiency lesions in higher primates. Higher glutathione transferase (or non-Se glutathione peroxidase) activity in tissues of rhesus monkeys may account for this resistance.     

Effects of feeding selenium deficient diets to rhesus monkeys (Macaca Mulatta)

Pregnant rhesus monkeys (Macaca mulatta) were fed either selenium (Se) deficient or Se supplemented diets with adequate vitamin E. Except for some cardiac irregularities in the first babies born to these females, no physiological disorders due to Se deficiency were seen in a subsequent offspring. Plasma and erythrocyte glutathione peroxidase activities and blood Se levels increased in the Se supplemented monkeys but decreased in the deficient ones. The data indicated that hair Se levels reflect long term exposure to this element. In a very preliminary experiment, evidence was obtained to indicate that dietary protein deficiency along with Se deficiency will generate cardiomyopathic lesions characteristic of Se deficiency. It is hypothesized that, in addition to Se deficiency, another dietary deficiency (or abnormality) is necessary to produce Se deficiency lesions in higher primates. Higher glutathione transferase (or non-Se glutathione peroxidase) activity in tissues of rhesus monkeys may account for this resistance.     

Growth, reproduction rates and mammary gland selenium concentration and glutathione-peroxidase activity of BALB/c female mice fed two dietary levels of selenium

This research was designed to determine the effect of various levels of dietary selenium on growth of BALB/c female mice. The selenium concentration and glutathione peroxidase (GSH-Px) activity in different developmental stages of the mammary gland was determined in the female mice fed 0.03 and 1.5 ppm Se. The development stages studied were: virgin (at 20 and 26 weeks of age), pregnant, lactating and involuted mammary gland. Also, the effect of the two levels of dietary selenium (0.03 and 1.5 ppm Se) on second generation reproductive rates were determined. There was no effect of dietary selenium (0.03, 0.20 or 2.00 ppm Se) on the growth rate of the mice except during pregnancy. The pregnant mice fed the 1.5 ppm Se diet had a greater growth rate than the mice fed the 0.03 ppm diet. Selenium levels in the mammary glands were higher in mice fed the 1.5 ppm Se diet than those fed the 0.03 p]pm Se diet. However, only in the mice with the highest growth rate, 10-week-old virgins, pregnant and lactating mice, was there an effect of dietary selenium on mammary gland GSH-Px activity. The reproductive rates for the second generation mice fed the two diets were similar to rates of mice fed stock diet. When both mating pairs (male and female) consumed the 0.03 ppm Se diet, the reproductive rates were lower than all other mating pairs. Thus, two conclusions can be made from these studies. First, as measured by growth and reproductive capabilities there were no signs of toxicity in mice fed the 1.5-2.0 ppm Se diet. Secondly, the differentiative states of the mammary gland influenced the selenium requirement for GSH-Px activity     

Effect of selenium depletion and repletion on plasma glutathione and glutathione-dependent enzymes in the rat

Selenium deficiency has several known biochemical effects. In the rat, these effects include loss of glutathione peroxidase (GSH-Px) activity, increased plasma glutathione concentration and increased liver glutathione S-transferase (GSH S-Tr) activity. The time course of the development of these changes in rats fed selenium-deficient diets and the time course of reversal of these changes in selenium-deficient rats fed graded levels of selenium were determined. As selenium deficiency was produced, liver cytosolic and plasma GSH-Px activities decreased first and were less than 5% of control when plasma glutathione concentration and liver GSH S-Tr activity began to increase. Elevated liver GSH S-Tr activity in selenium-deficient rats was corrected by refeeding selenium at the lowest level of supplementation (0.015 ppm) for 4 wk. GSH-Px activity required a supplementation of 0.10 ppm selenium for correction to control levels in 4 wk. Based on these studies a classification of the severity of selenium deficiency into mild, moderate and severe categories is proposed. In addition, the effect of dietary sulfur amino acid supplementation on plasma glutathione concentration was studied.     

Effect of dietary selenium and vitamin E on the antioxiant defense systems of rat erythrocytes.

The effect of dietary selenium and vitamin E on the important cellular antioxidant defense systems was studied in rat erythrocytes. Weanling male Sprague-Dawley rats were fed a basal selenium and vitamin E deficient diet and supplemented with either none or 0.5 ppm selenium and either none or 45 ppm vitamin E for 35 or 40 days. Depletion of dietary selenium resulted in marked decrease of glutathione (GSH) peroxidase in the red cells, but the levels of GSH, catalase and superoxide dismutase were not significantly altered. The red cells of rats fed the basal diet deficient in both selenium and vitamin E had significantly lower levels of GSH and GSH peroxidase, but not of catalase and superoxide dismutase, than in those fed the basal diet and supplemented with either selenium, vitamin E or both. The results suggest that depletion of dietary selenium and vitamin may have a precipitate effect on lowering the levels of GSH and GSH peroxidase in rat erytyrocytes.     

Some effects of vitamin E and selenium deprivation on tissue enzyme levels and indices of tissue peroxidation in rainbow trout (Salmo gairdneri)

Duplicate groups of rainbow trout (Salmo gairdneri) (mean weight 11 g) were given for 40 weeks one of four partially purified diets that were either adequate or low in selenium or vitamin E or both. Weight gains of trout given the dually deficient diet were significantly lower than those of trout given a complete diet or a diet deficient in Se. No mortalities occurred and the only pathology seen was exudative diathesis in the dually deficient trout. There was significant interaction between the two nutrients both with respect to packed cell volume and to malondialdehyde formation in the in vitro NADPH-dependent microsomal lipid peroxidation system. Tissue levels of vitamin E and Se decreased to very low levels in trout given diets lacking these nutrients. For plasma there was a significant effect of dietary vitamin E on Se concentration. Glutathione (GSH) peroxidase (EC 1.11.1.9) activity in liver and plasma was significantly lower in trout receiving low dietary Se but was independent of vitamin E intake. The ratios of hepatic GSH peroxidase activity measured with cumene hydroperoxide and hydrogen peroxide were the same for all treatments. This confirms the absence of a Se-independent GSH peroxidase activity in trout liver. Se deficiency did not lead to any compensatory increase in hepatic GSH transferase (EC 2.5.1.18) activity; values were essentially the same in all treatments. Plasma pyruvate kinase (EC 2.7.1.40) activity increased significantly in the trout deficient in both nutrients. This was thought to be due to leakage of the enzyme from the muscle and may be indicative of incipient (subclinical) muscle damage.     

Effects of vitamin B-6 deficiency on selenium metabolism in the rat

Rats were fed for 23 d diets adequate or deficient in vitamin B-6 and containing selenium as either sodium selenite, selenocysteine (SeCys) or selenomethionine (SeMet). They were then injected with 75Se of the same chemical form and killed 2 d later. Tissue deposition of stable and radiotracer selenium and the activity of glutathione peroxidase (GSHPx) were used to assess selenium utilization. Erythrocyte levels of selenium and GSHPx were lower in vitamin B-6--deficient animals for all forms of selenium; however, 75Se deposition in erythrocytes was not affected by vitamin B-6 status. The activities of cystathionine lyase, aspartate aminotransferase and selenocysteine lyase were lower in livers of vitamin B-6--deficient rats than in vitamin B-6--supplemented rats. The proportion of liver and kidney 75Se soluble in 5% trichloroacetic acid and 0.1 M 2-mercaptoethanol was consistently lower in vitamin B-6--deficient animals, but cation-exchange chromatography of tissue extracts did not identify a specific low-molecular-weight species. Tissue retention of 75Se provided as SeMet was increased in vitamin B-6--deficient animals, but the proportion of 75Se retained in muscle and liver as SeCys was significantly reduced. These findings suggest that the conversion of SeMet to a form available for GSHPx synthesis is reduced by vitamin B-6 deficiency.     

Effects of dietary zinc and cadmium on tissue selenium concentration and glutathione peroxidase activity in rats fed DL-selenomethionine or sodium selenite.

The effects of dietary zinc (Zn) and cadmium (Cd) on tissue selenium (Se) concentration and glutathione peroxidase (GSH-Px) activity were studied in weanling male Wistar rats. One group of rats was fed a purified diet based on casein and sucrose, and the other rats used in a 2 x 2 x 2 factorial arrangement of treatment were fed this diet supplemented with 0.1 mg Se/kg, either as DL-selenomethionine or sodium selenite and plus 100 mg Zn/kg as zinc sulfate or 5 mg Cd/kg as cadmium chloride or both for 4 weeks. Se concentrations in plasma, erythrocytes, muscle, heart, and liver were significantly elevated by Zn. Cd significantly decreased Se concentration in muscle. Addition of Zn to the diets markedly increased (p less than 0.001) hepatic GSH-Px activity. However, Cd in the diets produced a significant increase (p less than 0.001) in erythrocyte GSH-Px activity. These results indicate that Zn level of marginal deficiency (8.6 mg/kg diet) can decrease Se availability and a small excess of Zn increases Se availability for hepatic GSH-Px activity.     

Selenium and vitamin E status of healthy and institutionalized elderly subjects: analysis of plasma, erythrocytes and platelets

Levels of selenium in whole blood, plasma, erythrocytes and platelets, glutathione peroxidase (EC 1.11.1.9; GSH-Px) activity in erythrocytes and platelets and vitamin E, low-density-lipoprotein (LDL)-cholesterol and vitamin E: LDL cholesterol in plasma were measured in seventy-five healthy subjects aged less than 65 years and twenty-eight healthy and twenty-three institutionalized elderly people aged greater than 65 years. Healthy elderly subjects had significantly lower levels of Se in whole blood and plasma when compared with younger subjects. Other measurements of Se status were not significantly different. In the healthy subjects plasma levels of vitamin E and LDL-cholesterol increased with age to 60 years and decreased above 80 years. Vitamin E: LDL cholesterol values were not affected by age. Measurements of Se and vitamin E status in the institutionalized elderly compared with the healthy elderly were all reduced with the exception of platelet Se levels and erythrocyte GSH-Px activity. Ageing per se had minimal effect on Se and vitamin E status but intercurrent illness and decreased food intake can lead to reduced levels in the elderly.     

The effect of progressive selenium deficiency on anti-glutathione peroxidase antibody reactive protein in rat liver

Liver glutathione peroxidase (GSH-Px, EC 1.11.1.9) activity decreases when weanling rats are fed a Se-deficient diet. To determine the effect of dietary Se deficiency on the concentration of the protein portion of GSH-Px, weanling rats were fed a Se-deficient (less than 0.02 ppm Se) or a Se-supplemented (0.2 ppm Se as Na2SeO3) 30% torula yeast-based diet and killed 0, 3, 7, 14, 21 or 28 d later. GSH-Px activity was assayed using H2O2, so only the Se-dependent GSH-Px was measured. Anti-GSH-Px antibodies, produced in a rabbit by three injections of purified rat liver GSH-Px, were used in an enzyme-linked immunosorbent assay for GSH-Px protein. Immunoblotting showed that the antibodies were highly specific for GSH-Px. In Se-supplemented rats, liver GSH-Px activity increased 66% and GSH-Px protein increased 50% over the 28 d. In Se-deficient rats, liver GSH-Px activity decreased exponentially to zero with a half-life of 2.8 d. Liver GSH-Px protein also decreased exponentially, but with a longer half-life of 5.2 d (P less than 0.001), and the anti-GSH-Px antibody-reactive protein did not decrease to zero. This experiment shows that both GSH-Px activity and GSH-Px protein decrease exponentially during progressive dietary Se deficiency. The longer half-life of GSH-Px protein compared with GSH-Px activity suggests that an inactive GSH-Px polypeptide is present in rat liver during the early stages of Se deficiency.     

Effect of vitamin E,selenium and age on lipid peroxidation events in rat cerebrum

The effect of 8 and 20 weeks of dietary vitamin E (200 IU/kg diet) and/or selenium (0.2 ppm) supplementation or deficiency on oxidative processes in cerebrum of 1 and 15 month old male F344 rats was examined. After 8 weeks of treatment a 32-fold difference in plasma and a 3-fold difference in cerebrum alpha-tocopherol (a-T) level was found between vitamin E supplemented and deficient young rats. These differences were 1.8- and 1.5-fold, respectively, in old rats and increased to 8- and 2-fold differences, respectively, after an additional 12 weeks of treatment. Selenium deficiency had a significant effect on plasma glutathione peroxidase activity and a slight sparing effect on plasma a-T content. Endogenous lipid peroxides (thiobarbituric acid reactants present without incubation) in cerebrum were not correlated with a-T concentration or age. However, incubation of cerebrum homogenates with or without the addition of 0.1 mM Fe²⁺, 0.25 mM ascorbic acid, or 100 mg % acetaldehyde revealed that dietary vitamin E has a major role and selenium has a minor role in the protection against ex-vivo and possibly in vivo lipid peroxidation in cerebrum.     

Role of dietary vitamin E in cadmium-induced oxidative damage in rabbit's blood, liver and kidneys

The aim of this work was to determine the effect of dietary vitamin E intake on lipid peroxidation (LPO) by measuring thiobarbituric acid reactive substances (TBARS), vitamin E and reduced glutathione (GSH) levels, and glutathione peroxidase (GSH-Px: EC 1.11.1.9) activity in plasma, red blood cells (RBC), livers, and kidneys of rabbits dosed with cadmium (Cd). Six-month-old clinically healthy New Zealand White rabbits (8 in each group) were given tap water only, containing 1 g CdCl2/L, or tap water with CdCl2 plus vitamin E (100 mg dl-alpha-tocopheryl acetate in 0.2 mL corn oil) daily for 30 days. The vitamin E level in the plasma, liver, and kidneys was significantly higher in the control than in the Cd-only group, and TBARS levels were significantly lower. There were no statistical differences between the control and Cd-only groups GSH-Px activities and GSH levels in RBC, liver, and kidneys. Vitamin E levels in plasma, liver, and kidneys and GSH-Px activity in RBC were higher in the vitamin E group than in both control and Cd-only groups. However, the TBARS levels of RBC, liver, and kidneys in vitamin E administered group were decreased. Therefore, the present study demonstrates the effectiveness of vitamin E in reducing oxidative stress in Cd-treated rabbits and suggests that reductions in increased TBARS due to Cd toxicity may be an important factor in the action of vitamin E.