Effect of dietary supplementation with selenium-enriched yeast or sodium selenite on selenium tissue distribution and meat quality in commercial-line turkeys

The objective of this study was to determine the concentration of total selenium (Se) and proportions of total Se comprised as selenomethionine (SeMet) and selenocysteine (SeCys) in the tissues of female turkeys offered diets containing graded additions of selenized-enriched yeast (SY), or sodium selenite (SS). Oxidative stability and tissue glutathione peroxidase (GSH-Px) activity of breast and thigh muscle were assessed at 0 and 10 days post mortem. A total of 216 female turkey poults were enrolled in the study. A total of 24 birds were euthanized at the start of the study and samples of blood, breast, thigh, heart, liver, kidney and gizzard were collected for determination of total Se. Remaining birds were blocked by live weight and randomly allocated to one of four dietary treatments (n = 48 birds/treatment) that differed either in Se source (SY v. SS) or dose (Con [0.2 mg/kg total Se], SY-L and SS-L [0.3 mg/kg total Se as SY and SS, respectively] and SY-H [0.45 mg total Se/kg]). Following 42 and 84 days of treatment 24 birds per treatment were euthanized and samples of blood, breast, thigh, heart, liver, kidney and gizzard were retained for determination of total Se and the proportion of total Se comprised as SeMet or SeCys. Whole blood GSH-Px activity was determined at each time point. Tissue GSH-Px activity and thiobarbituric acid reactive substances were determined in breast and thigh tissue at the end of the study. There were responses (P < 0.001) in all tissues to the graded addition of dietary Se, although rates of accumulation were highest in birds offered SY. There were notable differences between tissue types and treatments in the distribution of SeMet and SeCys, and the activity of tissue and erythrocyte GSH-Px (P < 0.05). SeCys was the predominant form of Se in visceral tissue and SeMet the predominant form in breast tissue. SeCys contents were greater in thigh when compared with breast tissue. Muscle tissue GSH-Px activities mirrored SeCys contents. Despite treatment differences in tissue GSH-Px activity, there were no effects of treatment on any meat quality parameter.     

富硒产品中硒的形态分析及化学评分模式的建立

采用微波水解、HPLC-HG-AFS法测定了硒蛋白粉、硒蛋白片、肽粉、富硒原料等19种硒产品中的总硒、硒代氨基酸和亚硒酸根离子[Se(IV)],分析了硒代氨基酸、Se(IV)和其他形态硒占总硒的百分比及不同形态硒代氨基酸的组成比例。以此为依据,将硒产品分为硒蛋白型、单一硒代氨基酸型、其它形态硒型及有机无机硒混合型。根据DBS42/002-2014规定建立了富有机硒产品评分模式,其中18种为富有机硒产品;根据适硒地区母乳中硒代氨基酸的组成比例提出了硒代氨基酸的化学评分模式,评分结果显示13种以蛋白态硒为主的硒产品中硒代氨基酸的组成比例均与母乳相差甚远,不利于人体平衡吸收利用,其中10种SeMet含量远远超过人体所需,SeCys_2为限制硒代氨基酸。该评分模式的建立对硒产品的开发具有指导意义。     

The effect of nationwide selenium enrichment of fertilizers on selenium status of healthy finnish medical students living in south western Finland

In Finland commercial fertilizers have been enriched with sodium selenate since July 1, 1984 in order to compensate for the poor selenium content of the soil. Fertilizers that are used for the production of hay and fodder were supplemented with 6 mg/kg of selenium, whereas fertilizers used for the production of cereals were supplemented with a higher dose, 16 mg/kg fertilizer. The effects of selenium fertilization were first seen in dairy products in June 1985, and from the beginning of August 1985, the effect was evident also in wheat flour, beef, and bovine liver. In this study the selenium status of 108 healthy young adults has been systematically documented since November 1985, at which time the mean selenium serum level (S-Se) was 1.05 umol/L. A steady increase was observed until November 1989, when the maximum level, with a mean of S-Se 1.6 umol/L was reached. After that, a slight decrease has occurred. The mean serum selenium level in autumn 1991 in a new group of 35 students was 1.58 umol/L. This decrease can be explained by the high amount of imported cereals in 1988 and 1989, which was reflected also in the serum selenium levels. The glutathione peroxidase activity in erythrocytes in 1989–1990 was at the same level as in 1985 and 1986.     

Effects of nationwide addition of selenium to fertilizers on foods,and animal and human health in Finland: From deficiency to optimal selenium status of the population

Despite different geological features the Nordic countries are generally selenium-poor areas. In each country various factors such as food importation and life-style determine the selenium (Se) intake. Due to an extremely low Se intake in the 1970s in Finland, 0.025 mg/day, an official decision was made in 1984 to supplement multinutrient fertilizers with Se in the chemical form of sodium selenate. Almost all fertilizers used in Finland since 1985 have contained Se. Currently all crop fertilizers contain 15 mg Se/kg. Finland is still the only country to take this country-wide measure.In a national monitoring programme, sampling of cereals, basic foodstuffs, feeds, fertilizers, soils, and human tissues has been carried out annually since 1985 by four governmental research organizations. Sampling of foods has been done four times per year and human blood has been obtained annually from the same (n = 60) adults. The accuracy of analyses has been verified by annual interlaboratory quality control. During this programme the selenium concentration of spring cereals has increased on average 15-fold compared with the level before the Se fertilization. The mean increase in the Se concentration in beef, pork and milk was 6-, 2- and 3-fold. In terms of Se, organically grown foods of plant origin are generally comparable to products produced before the Se supplementation of fertilizers. Milk from organically fed cows is 50% lower in Se than the usual milk. The average dietary human intake increased from 0.04 mg Se/day/10 MJ in 1985 to a present plateau of 0.08 mg Se/day/10 MJ, which is well above the current nutrition recommendations. Foods of animal origin contribute over 70% of the total daily Se intake. The mean human plasma Se concentration increased from 0.89 μmol/L to a general level of 1.40 μmol/L that can be considered to be an optimal status. The absence of Se deficiency diseases and a reference population have made conclusions on the impact on human health difficult. However, the rates of cardiovascular diseases and cancers have remained similar during the pre- and post-supplementation indicating medical and life-style factors to be much stronger determinants than Se. The nationwide supplementation of fertilizers with sodium selenate is shown to be effective and safe in increasing the Se intake of the whole population. Also, the health of animals has improved.     

Effects of long-term selenium yeast supplementation on selenium status studied in the rat

To investigate the selenium status during long-term dietary supply of selenium yeast, 30-day-old male rats were fed for 379 days a methionine-adequate low-selenium diet supplemented with 0.2 mg Se/kg (selenium-adequate diet) or 1.5 mg Se/kg (high-selenium diet) in the form of selenium yeast that contained 60% of the element as l-selenomethionine. Their selenium load was determined at several intervals by neutron activation analysis of the selenium concentrations in the main selenium body pools, skeletal muscle and liver. After 64 days the tissue selenium concentrations plateaued in both groups and then stayed at that level. Compared with the selenium-adequate group, elevated tissue selenium concentrations were found in the high-selenium group, but the increase by a factor of 3.5 in the muscle and by a factor of 2.3 in the liver was smaller than the 7.5-fold increase in the selenium intake. In the selenium-adequate group about 50% of the muscle selenium and 30% of the liver selenium and in the high-selenium group about 85% of the muscle selenium and 70% of the liver selenium were estimated to be present in non-selenoprotein forms. During selenium depletion the liver glutathione peroxidase activity in the high-selenium group remained unaffected for 4 weeks and then decreased more slowly than that in the selenium-adequate group. From these results it can be concluded that selenium incorporated from the selenium yeast diet into non-selenoprotein forms can serve as an endogenous selenium source to maintain selenoprotein levels in periods of insufficient selenium supply.     

Gestational changes in concentrations of selenium and zinc in the porcine fetus and the effects of maternal intake of selenium

The effect of maternal dietary selenium (Se) and gestation on the concentrations of Se and zinc (Zn) in the porcine fetus were determined. Mature gilts were randomly assigned to treatments of either adequate (0.39 ppm Se) or low (0.05 ppm Se) dietary Se. Gilts were bred and fetuses were collected throughout gestation. Concentrations of Se in maternal whole blood and liver decreased during gestation in sows fed the low-Se diet compared to sows fed the Se-supplemented diet. Maternal intake of Se did not affect the concentration of Se in the whole fetus; however, the concentration of Se in fetal liver was decreased in fetuses of sows fed the low-Se diet. Although fetal liver Se decreased in both treatments as gestation progressed, the decrease was greater in liver of fetuses from sows fed the low-Se diet. Dietary Se did not affect concentrations of Zn in maternal whole blood or liver or in the whole fetus and fetal liver. The concentration of Se in fetal liver was lower but the concentration of Zn was greater than in maternal liver when sows were fed the adequate Se diet. These results indicate that maternal intake of Se affects fetal liver Se and newborn piglets have lower liver Se concentrations compared to their dams, regardless of the Se intake of sows during gestation. Thus, the piglet is more susceptible Se deficiency than the sow.     

Changes in selenium, zinc, copper and cadmium contents in human milk during the time when selenium has been supplemented to fertilizers in Finland

Sodium selenate has been supplemented to all agricultural fertilizers used in Finland since 1984. We followed the changes in selenium, cadmium, zinc and copper content in Finnish human milk between the years 1987 and 1993-1995. A total of 257 milk samples was collected, four weeks after delivery, in two areas: In Helsinki, an urban area, and in Kuopio, a rural area, where elevated copper concentrations have been found in the bedrock. Direct atomic absorption spectrophotometric methods without digestion were used for the analyses. The dependence of trace element content on study time, living area, smoking habits, fish eating frequency, and parity of mothers was studied by analysis of covariance. Inter-element correlations and correlations with mothers' age and fat content in milk were studied by partial correlation. Significant increases were observed in mean selenium (16.4 microg/l and 18.9 microg/l, p < 0.001) and in fat contents (3.4% and 4.0%, p < 0.001), whereas significant decreases were seen in mean zinc (3.00 mg/l and 1.47 mg/l, p < 0.001), copper (0.52 mg/l and 0.43 mg/l, p < 0.001) and cadmium contents (0.095 microg/l and 0.062 microg/l, p < 0.01). In 1987, zinc had a positive correlation with copper and fat. Copper correlated inversely with the mothers' age. In 1993-1995, selenium correlated positively with copper, and zinc correlated inversely with mothers' age. Mothers living area had an effect on copper content in milk. Our results confirm that selenium supplementation to fertilizers in Finland has increased the selenium level in human maternal milk and most likely it also has an effect on the zinc and copper concentrations in maternal milk.     

Concurrent quantitative HPLC–mass spectrometry profiling of small selenium species in human serum and urine after ingestion of selenium supplements

Selenium metabolic patterns in the human body originating from five distinct selenium dietary sources, selenate, selenite, selenomethionine (SeMet), methylselenocysteine (MeSeCys) and selenized yeast, were investigated by performing concurrent HPLC–mass spectrometric analysis of human serum and urine. Total selenium and selenium species time profiles were generated by sampling and analyzing serum and urine from volunteers treated with selenium supplements, up to 5 and 24 h following ingestion, respectively. We found that an increase in total serum selenium levels, accompanied by elevated selenium urinary excretion, was the common pattern for all treatments, except for that of selenite supplementation. Selenosugar 1 was a universal serum metabolite in all treatments, indicating that ingested selenium is favorably metabolized to the sugar. Except for selenite and selenized yeast ingestion, these patterns were reflected in the urine time series of the different treatments. Selenosugar 1 was the major selenium species present in urine in all treatments except for the selenate treatment, accounting for about 80% of the identified excreted species within 24 h of ingestion. Furthermore, the urinary metabolite trimethylselenonium ion (TMSe) was detected for the first time in human background serum by using HPLC coupled to elemental and molecular mass spectrometry. The concurrent monitoring of non-protein selenium species in both body fluids provides the relation between bioavailability and excretion of the individual ingested species and of their metabolic products, while the combined use of elemental and molecular mass spectrometry enables the accurate quantitation of structurally confirmed species. This successfully applied approach is anticipated to be a useful tool for more extensive future studies into human selenium metabolism.     

环境中硒的生物地球化学循环和营养调控及分异成因

硒是环境中重要的生命元素,它在环境中含量水平的高低直接影响着人及动植物的健康安全。结合国内外资料及最新的研究进展,阐述了环境中硒的生物地球球化学循环,包括环境中硒的生物地球化学循环特征,土壤中硒的含量分布、形态及有效性,大气和水环境中硒的形态分布,植物体中的硒及其对硒的吸收关系;讨论了低硒高硒环境中硒营养水平的调节及环境分异的成因,诸如母质类型、气候特征、风化淋失、气体挥发、土壤质地和地力耗竭等方面;并提出了环境中硒研究的前沿及今后关注的热点问题,以促进今后环境中硒的研究。     

Evidence for the antimutagenicity and the mutagenicity of selenium

Evidence is summarized for the antimutagenicity as well as the mutagenicity of selenium. In general, antimutagenicity predominates at physiological levels, while mutagenicity occurs at 3 to 1000 times normal physiological levels.     

Colostrum and milk selenium,antioxidative capacity and immune status of dairy cows fed sodium selenite or selenium yeast

Dietary selenium (Se) can be supplemented from organic or inorganic sources and this may affect Se metabolism and functional outcome such as antioxidative status and immune functions in dairy cows. A feeding trial was performed with 16 Holstein-Friesian dairy cows fed with a total mixed ration (0.18 mg Se/kg dry matter (DM)) either without Se supplement (Control, n = 5), or with Se from sodium selenite (Group SeS, n = 5) or Se yeast (Group SeY, n = 6). In Groups SeS and SeY, the Se supplementation amounted to an additional intake of 4 mg Se and 6 mg Se/d during gestation and lactation, respectively. The effect of both Se sources was characterised by milk Se and antioxidant levels, and the phenotyping and functional assessment of phagocytic activity of milk immune cells. Se yeast has been found to increase (p ≤ 0.001) the milk Se and antioxidant levels markedly compared to the control group. The experimental treatment did not affect the immune parameters of the cows. Lymphocyte subpopulations and phagocytosis activity of neutrophilic granulocytes were affected neither by the Se intake nor by the two different dietary supplements. It can be concluded that sodium selenite and Se yeast differ considerably in their effects on antioxidant status in dairy cows. However, the basal dietary Se concentration of 0.18 mg/kg DM seemed to be high enough for the measured immune variables.     

Characterization of selenium status of inhabitants in the region Ústi nad orlici,czech republic by inaa of blood serum and hair and fluorimetric analysis of urine

Selenium is an essential trace element and its isufficient status may cause serious health complications for both individuals and the whole populations. To investigate the selenium status of the subpop-ulation in northeastern Bohemia represented by the region ústí nad Orlicí, 253 serum, 469 urine, and 31 hair samples from 470 randomly selected volunteers between 6 and 65 yr of age have been analyzed for selenium concentration. Serum and hair Se were detected by instrumental neutron activation analysis (means: 55 ±11 Μg Se/L sera, 0.268 ±0.040 Μg Se/g hair). Urine Se was measured by fluorimetry (12 ±5 Μg Se/L urine) with coanalyses of Lyphocheck urine, SRM Urine 2670, and Seronorm urine for quality control of the method. Results proved significant age-dependent differences, but gender differences were not significant. The frequency plot of serum Se proved maximal frequencies in adults between 55 and 70 Μg Se/L and in children in the range 45–55 Μg Se/L. The same plots of urine Se for both age groups showed maximal frequency in the limits 8–15 Μg Se/L. All indices used (Se in serum, urine, and hair) confirmed mild to severe selenium deficiency in the population of the region.     

Effect of selenium deficiency on the antioxidative status and muscle damage in growing turkeys

An experiment investigated the effect of different selenium supplementations on the antioxidant defence system and on the occurrence of muscle dystrophy in growing turkeys. Newly hatched male turkeys (B.U.T. Big 6) were divided into eight groups of 18 turkeys each and fed either a basal diet (selenium <0.010 mg/kg diet), or the basal diet supplemented with 0.10; 0.15; 0.20; 0.25; 0.30; 0.35 or 0.40 mg selenium/kg diet in the form of sodium selenate. Vitamin E was adequately supplemented in all diets. After 35 days, muscle damage parameters including aspartate aminotransferase, creatine kinase, creatine kinase M and B were significantly increased in the selenium deficient Group I. A significant reduction of weight gain, feed consumption and selenium dependent glutathione peroxidase activity was also observed in the liver of selenium deficient birds. The ratio of oxidised glutathione (GSSG) to total glutathione (tGSH) was substantially altered in the selenium deficient Group I as well as in Group II (0.10 mg selenium/kg feed). The activity of glutathione reductase (GR) and glutathione-S-transferase (GST) was not affected by selenium deficiency.     

Effect of dietary supplementation with different sources of selenium on growth response, selenium blood levels and meat quality of intensively finished Charolais young bulls

The study aimed at comparing three strategies of supplementing selenium (Se) during the finishing period of Charolais young bulls: (1) administration of sodium selenite throughout the finishing (NaSe); (2) administration of an Se-enriched yeast strain (Saccharomyces cerevisiae NCYC R397) throughout the finishing (Se-Y); (3) administration of sodium selenite for 140 days replaced by Se-enriched yeast during the last 70 days of finishing (Switch). Eighty-four young bulls (mean initial BW=434.2±31.9 kg; mean age=382±52 days) were stratified by live weight and equally assigned to one of three Se treatments. Experimental groups were fed the same diets and the inclusion rate of the different treatments was targeted to achieve 0.3 mg of Se/kg of dry matter (DM) in the complete feed. The average daily gain of bulls was 1.36 kg/d and no differences due to Se treatment were recorded. Dry matter intake and feed conversion ratio were not affected by Se treatment resulting in, on average, 10.3 kg/d and 7.65, respectively. Repeated blood samples were taken at days 0, 120, 180 and 210 of finishing to assess the Se status of the animals. As compared to NaSe, both organic Se treatments (Se-Y and Switch) increased plasma Se in the last two sampling sessions according to a significant treatment×time interaction (P<0.001). A similar trend was observed for serum total antioxidant status of the young bulls, whereas there was only a significant time effect (P<0.001) on glutathione peroxidase activity that was raised by all Se treatments. The finishing period lasted 210 days and at the abattoir there were no differences across Se treatments in carcass weight and dressing percentage. A higher Se content in the Longissimus thoracis (LT) muscle was instead observed in Se-Y samples as compared with NaSe (0.85 v. 0.47 mg/kg DM; P<0.05). Meat quality evaluation was carried out on LT samples after 6 and 11 days of ageing under a vacuum package. Regardless of ageing time, meat from young bulls supplemented with Se yeast had higher colour lightness (L*) values than those receiving NaSe (38.1 v. 36.6; P<0.01) and showed a significant decrease in shear force (3.69 v. 4.22 kg/cm2; P<0.01). The outcomes of the study suggest that the provision of Se yeast throughout the finishing period is a strategy to increase the benefits of the replacement of sodium selenite with organic selenium in beef cattle.     

Effect of supplementation with selenium on whole blood glutathione peroxidase activities and on plasma and tissue selenium concentrations in lambs

In recent years the selenium (Se) intake of the human population of the UK has shown a marked decline from 60 μg/d in 1978 to around 30 μg/d in 1990 owing largely to a significant reduction in the importation of North American wheat for bread-making fluor. Other countries (Finland, for example) in similar situations have instituted fertilization programs in order to raise cereal Se concentrations and thus boost dietary intakes. An alternative approach would be to increase the Se concentration of carcass meat by supplementation of meat animals for a limited period prior to slaughter. A trial was set up with store lambs to evaluate this approach. Sixteen Scottish Blackface lambs were stratified according to live weight and then randomly allocated to one of four treatments: unsupplemented, or 3.5, 7, or 10.5 mg. Se/head/wk. After 14 wk, the lambs were sacrificed and samples of shoulder and thigh muscle, liver, and kidney were obtained for analysis. All three treatments effected an increase in whole blood glutathione peroxidase (GSH-Px) and plasma Se concentrations over controls. Shoulder, thigh, and liver Se exhibited a dose-response relationship to treatment, but kidney Se concentrations were unaffected by treatment. Muscle and some organ meat Se concentrations can therefore be increased by supplementation and could contribute to increased human dietary intakes of the element.     

Effects of low selenium diets on antioxidant status and MPTP toxicity in mice

To investigate the role of chronic oxidative stress in MPTP neurotoxicity, C57BL mice were maintained 6–8 weeks on diets deficient in nutrients essential to cellular antioxidant defenses, selenium (Se) and alpha-tocopherol (vit E), and the effects on tissue antioxidant status and MPTP toxicity were evaluated relative to controls on supplemented diets. Activities of the major antioxidant enzymes, glutathione peroxidase (GPx), catalase, and superoxide dismutase, and levels of malondialdehyde as a marker for oxidative stress, were measured in brain, lung, liver and blood. Caudate depletion of dopamine and its metabolites served as a measure of MPTP neurotoxicity. For mice on the Se deficient diet, levels of the selenoenzyme GPx decreased from 50% in brain to 90% in blood. No compensatory changes in the activities of the other antioxidant enzymes were observed and addition of vit E to the diet did not alter antioxidant enzyme activities or malondialdehyde levels. In animals not treated with MPTP, the Se deficient diet significantly increased malondialdehyde only in liver. No protective effect of the antioxidant supplements against caudate depletion of dopamine and its metabolites was observed. However, malondialdehyde levels were increased in the brains of MPTP treated mice on the low Se diets, suggesting the possibility of secondary oxidative damage to tissues accompanying the destruction of substantia nigra neurons by MPTP.     

Nutritional status of the Indian population

High prevalence of low birth weight, high morbidity and mortality in children and poor maternal nutrition of the mother continue to be major nutritional concerns in India. Although nationwide intervention programmes are in operation over two decades, the situation has not changed greatly. In addition, the Indian population is passing through a nutritional transition and is expected to witness higher prevalences of adult non-communicable diseases such as diabetes, hypertension and coronary heart disease according to the theory of ‘fetal origin of adult disease’. Clearly, there is a need for examining several issues of nutritional significance for effective planning of interventions. In particular, maternal nutrition and fetal growth relationship, long term effects of early life undernutrition, interactions of prenatal nutritional experiences and postnatal undernutrition are some of the major issues that have been discussed in the present paper with the help of prospective data from various community nutrition studies carried out in the department.     

Early evolution of selenium status and oxidative stress parameters in rat models of thermal injury

The objective of the present study was to measure the relationship between selenium status and oxidative stress in two rat models of thermal injury. A non-lethal third-degree burn injury involving 20% (experiment 1) or 40% (experiment 2) of total body surface area (TBSA) was applied to male Wistar rats. Selenium level, glutathione peroxidase (GPx) activity in plasma, red blood cells (RBC) and tissues (liver, kidney, muscle, and brain), and plasma selenoalbumin (Se-alb) were measured in control rats and in burned rats respectively 6 hours after injury and daily from day 1 to day 5. In parallel, lipid and protein oxidative damages, monitored by plasma and tissue thiobarbituric acid reactive species (TBARs) levels and plasma total thiol groups were assessed.

We observed a decrease of plasma Se and Se-albumin 6 hours after burn injury. In parallel, plasma GPx activity rapidly decreased and remained significantly lower than in control rats. These alterations were enhanced by the burn injury severity. Plasma TBARs followed the same pattern as that of plasma cholesterol, with an initial decrease and an increase at day 3 in 40% TBSA burned rats. Plasma thiol groups decreased in the two experiments indicating plasma protein oxidation.

These results confirm an early oxidative stress in burn injury, and suggest an early selenium mobilization, which might counteract this oxidative stress. These data underline the crucial need of a restored selenium status in burned patients immediately after the burn injury.     

Antioxidant and cytotoxic effect of biologically synthesized selenium nanoparticles in comparison to selenium dioxide

The present study was designed to evaluate antioxidant and cytotoxic effect of selenium nanoparticles (Se NPs) biosynthesized by a newly isolated marine bacterial strain Bacillus sp. MSh-1. An organic–aqueous partitioning system was applied for purification of the biogenic Se NPs and the purified Se NPs were then investigated for antioxidant activity using DPPH scavenging activity and reducing power assay. Cytotoxic effect of the biogenic Se NPs and selenium dioxide (SeO₂) on MCF-7 cell line was assesed by MTT assay. Tranmission electron micrograph (TEM) of the purified Se NPs showed individual and spherical nanostructure in size range of about 80–220 nm. The obtained results showed that, at the same concentration of 200 μg/mL, Se NPs and SeO₂ represented scavenging activity of 23.1 ± 3.4% and 13.2 ± 3.1%, respectively. However, the data obtained from reducing power assay revealed higher electron-donating activity of SeO₂ compared to Se NPs. Higher IC₅₀ of the Se NPs (41.5 ± 0.9 μg/mL) compared to SeO₂ (6.7 ± 0.8 μg/mL) confirmed lower cytotoxicity of the biogenic Se NPs on MCF-7 cell line.     

Glutathione contributes to the efflux of selenium from hepatoma cells

Selenite is a selenium source for selenoprotein biosynthesis in mammalian cells. Although previous studies have suggested the involvement of glutathione (GSH) and/or thioredoxin reductase in selenite metabolism, intracellular selenite metabolism remains largely unknown. Here, we report that GSH depletion did not affect the amount of selenoprotein in Hepa 1–6 cells, suggesting that GSH does not play a central role in the reduction of selenite in selenoprotein biosynthesis. On the other hand, we found that GSH is involved in the efflux of low-molecular-weight selenium compounds from cells, presumably via the formation of selenodiglutathione. Moreover, selenite inhibited the efflux of a fluorescent bimane-GS conjugate that is mediated by ATP-dependent multidrug-resistant proteins, implying the existence of an active transporter for selenodiglutathione. This is the first report demonstrating that GSH plays a role in selenium excretion from cells by forming a GSH-conjugate, which may contribute to the distribution, detoxification, and homeostasis of selenium in the body.