Low Doses Of Se Research Articles

Interactive Effects between Zinc and Selenium on Mineral Element Accumulation and Fruit Quality of Strawberry

In this study, we evaluated zinc (Zn) and selenium (Se) biofortification in strawberry fruits under substrate and soil cultivation, along with their effects on mineral element accumulation and fruit quality. To achieve this, foliar Zn (0.1% and 0.2%) and Se (0.003% and 0.006%) fertilizers were applied separately or in combination at the initial flowering stage. The Zn and Se contents in strawberry fruits increased with the spraying dosage. Compared to the control, the Zn content in the first batch of Zn-treated strawberries increased by 36.9–109% and 27.1–102% under substrate and soil cultivation, respectively, while Se increased by 313–444% and 21.3–53.3%, respectively. However, foliar Zn application could not ensure long-term sustainability as Zn in strawberries gradually decreased in the two subsequent batches, while Se was more stable. Compared to the control, the Se content in the three batches of Se2 (0.006%)-treated strawberries grown in soil increased by 32.9%, 124%, and 109%, respectively. Meanwhile, compared to Se alone, the Zn–Se combined application decreased the Se content in strawberries by 61.2–77.6% and 24.9–45.7% under substrate and soil cultivation, respectively, while low doses of Se promoted Zn enrichment (by 8.62–40.9%) and high doses inhibited it (by 13.2–28.9%) under substrate cultivation. Moreover, the copper content in strawberries under substrate cultivation after the Se1 (0.003%) treatment was significantly higher (by 75.0%) than that in the control. A positive correlation was observed between Cu and Zn contents in strawberries under both substrate and soil cultivation. A consistent positive impact was also observed on fruit quality. The Se2 (0.006%) treatment caused an increase in ascorbic acid content (by 37.2%) in strawberry fruits. The soluble sugar content increased by 36.3% after the Zn1 (0.1%) treatment. The present study provides a practical basis for the biofortification of strawberries with Zn and Se.

The effects of selenium on the growth and bone development in the weaned rats

Selenium is a crucial trace element, and a deficiency of selenium can cause oxidative stress damage and impede the growth and development of the body. L-Se-methylselenocysteine (L-SeMC) is a naturally occurring organic-selenium, which has higher bioavailability compared to inorganic-selenium such as Na2SeO3. In this study, weaned rats were fed with a selenium-deficient liquid diet to simulate the selenium-deficient breastfeeding. High and low doses of Se were supplemented in the liquid feed with L-SeMC and Na2SeO3, respectively. The results showed that the selenium-deficient diet reduced the growth rate and development of the weaned rats, leading to oxidative stress in the body and damaging liver and kidney function, as well as causing the histological lesions in heart and knee joints. Supplementing high doses (0.20 mg Se/kg) of L-SeMC and Na2SeO3 could increase the body weight of selenium-deficient rats by 10.48% and 4.47%, respectively. The symptoms caused by selenium deficiency were significantly relieved after supplementation with selenium, with L-SeMC being more effective than Na2SeO3. Furthermore, femoral bone mineral density (BMD) was increased by 77.0% with supplementation of L-SeMC in the selenium-deficient rats, while supplementation with Na2SeO3 resulted in only a 19.4% increase in BMD. These findings indicated that due to its higher bioavailability and superior ability to alleviate oxidative stress damage and growth retardation caused by selenium deficiency, L-SeMC is a better supplement for alleviating the oxidative stress and liver and kidney damage caused by selenium deficiency, and has a superior therapeutic effect on myocardial tissue and knee joint lesions compared to Na2SeO3.

Microbiota-Liver-Bile Salts Axis, a Novel Mechanism Involved in the Contrasting Effects of Sodium Selenite and Selenium-Nanoparticle Supplementation on Adipose Tissue Development in Adolescent Rats.

Adolescence is a period during which body composition changes deeply. Selenium (Se) is an excellent antioxidant trace element related to cell growth and endocrine function. In adolescent rats, low Se supplementation affects adipocyte development differently depending on its form of administration (selenite or Se nanoparticles (SeNPs). Despite this effect being related to oxidative, insulin-signaling and autophagy processes, the whole mechanism is not elucidated. The microbiota-liver-bile salts secretion axis is related to lipid homeostasis and adipose tissue development. Therefore, the colonic microbiota and total bile salts homeostasis were explored in four experimental groups of male adolescent rats: control, low-sodium selenite supplementation, low SeNP supplementation and moderate SeNPs supplementation. SeNPs were obtained by reducing Se tetrachloride in the presence of ascorbic acid. Supplementation was received orally through water intake; low-Se rats received twice more Se than control animals and moderate-Se rats tenfold more. Supplementation with low doses of Se clearly affected anaerobic colonic microbiota profile and bile salts homeostasis. However, these effects were different depending on the Se administration form. Selenite supplementation primarily affected liver by decreasing farnesoid X receptor hepatic function, leading to the accumulation of hepatic bile salts together to increase in the ratio Firmicutes/Bacteroidetes and glucagon-like peptide-1 (GLP-1) secretion. In contrast, low SeNP levels mainly affected microbiota, moving them towards a more prominent Gram-negative profile in which the relative abundance of Akkermansia and Muribaculaceae was clearly enhanced and the Firmicutes/Bacteroidetes ratio decreased. This bacterial profile is directly related to lower adipose tissue mass. Moreover, low SeNP administration did not modify bile salts pool in serum circulation. In addition, specific gut microbiota was regulated upon administration of low levels of Se in the forms of selenite or SeNPs, which are properly discussed. On its side, moderate-SeNPs administration led to great dysbiosis and enhanced the abundance of pathogenic bacteria, being considered toxic. These results strongly correlate with the deep change in adipose mass previously found in these animals, indicating that the microbiota-liver-bile salts axis is also mechanistically involved in these changes.

A selenium-enriched diet helps to recover liver function after antibiotic administration in mice.

Antibiotic (Abx) treatments or inadvertent exposure to Abx-contaminated food and water can adversely affect health. Many studies show strong correlations between Abx and liver damage pointing to gut dysbiosis as a contributing factor because the gut microbiota (GM) forms a complex network with liver. Selenium (Se) is a beneficial micronutrient able to shape the composition of the GM. We analyzed here the ability of a low dose (120μg/kg bodyweight/day) Se-enriched diet to ameliorate the effects of a 7-day intervention with an Abx-cocktail over the global health and the homeostasis of cholesterol and bile acids in the mouse liver. We found that Se restored lipid metabolism preventing the increased synthesis and accumulation of cholesterol caused by Abx treatment. Integrating these results with previous metataxonomic and metabolomic data in same mice, we conclude that part of the effect of Se against liver dysfunction (cholesterol and bile acids metabolism and transport) could be mediated by the GM. We provide data that contribute to a more complete view of the molecular mechanisms underlying the beneficial action of Se on health, pointing to a possible use of low doses of Se as a functional food additive (prebiotic) to prevent the negative effects of antibiotics.

Effect of selenium accumulation on foraging behavior of pollinators and seed yield in Trifolium alexandrinum L.

Selenium (Se) is an essential nutrient for both plants and animals and is usually provided as a supplement to livestock. Se bioaccumulation promotes plant growth by enhancing the accumulation of organic solutes and the activation of antioxidant system. In animals, the Se supplements reduce the chances of mastitis and white muscle disease, and improve the immunity, health, and reproduction, particularly in lactating dairy cows. Therefore, the enrichment or biofortification of fodder crops with Se may improve the nutritional quality of forages and thereby reduce malnutrition in cattle. However, Se hyper-accumulation in plants or plant parts can cause direct toxic effects on insects especially bees. Berseem is a highly cross-pollinated fodder crop that attracts a large number of pollinators. However, little or no reports are available regarding the effects of Se biofortification on the foraging behavior of pollinators in berseem. Therefore, the current study was planned to evaluate the effect of exogenous application of Se on the foraging behavior of native pollinators visiting the berseem crop. Five different doses of Se were applied to evaluate its effect on abundance, foraging behavior (visit duration and visitation rate), and single-visit efficacy of native pollinators that may affect berseem seed yield. Our results showed maximum abundance of pollinators in plants supplemented with low Se level, i.e., 5gha-1 while the minimum abundance was observed at high Se doses (15 and 20gha-1). Also, the seed yield attributes, i.e., the number of seeds per head, seed weight per head, 1000 seed weight, were the highest in plants treated with a low dose of Se, whereas the seed yield of berseem decreased with an increase in Se concentrations. Hence, our study provides evidence that high doses of Se negatively affect the foraging behavior of pollinators (visitation rate and visit duration) in plants. We conclude that the application of moderate Se dose positively influences the pollination ecology of berseem, consequently improving seed yield. HIGHLIGHTS: Selenium (Se) is essential for animals and beneficial for plants and may become toxic at high level. Se is delivered to the environment due to agriculture. Se toxicity affected berseem growth and considerably reduced the seed yield. High dose of Se reduced the abundance of pollinators and negatively affected their foraging behavior.

Fertilización foliar con selenito de sodio y su efecto sobre el rendimiento y calidad nutracéutica en el cultivo de vid

Selenium (Se) is an essential micronutrient for humans, but in plants, this essentiality has not been demonstrated. However, the supplementation of Se in crops has been shown to improve the yield and the quality of the edible part. The objective of this research was to evaluate the effect of Se foliar fertilization on yield, nutraceutical quality and Se accumulation in grape. Five doses of Se (Na2SeO3 at 0.25, 0.5, 0.75, 1.0 and 1.25 mg.L-1) and a control were evaluated. The results obtained showed that the application in low doses of Se increased the yield; high doses increase nutraceutical quality and induced the accumulation of Se in grapes. In conclusion, the grapevine is a crop with the potential to be biofortified and improve the quality of grape.

The Role of Selenium Nanoparticles in Agriculture and Food Technology.

Selenium (Se) is an essential micronutrient for diverse organisms such as mammals, bacteria, some insects and nematodes, archaea, and algae, as it is involved in a large number of physiological and metabolic processes and is part of approximately 25 selenoproteins in mammals. In plants, Se has no essential metabolic role, high concentrations of inorganic Se can lead to the formation of Se-amino acids, and its incorporation into selenoproteins can generate toxicity. Conversely, low doses of Se can trigger a variety of beneficial effects as an antioxidant, antimicrobial, or stress-modulating agent without being an essential element. Therefore, Se can generate toxicity depending on the dose and the chemical form in which it is supplied. Selenium nanoparticles (SeNPs) have emerged as an approach to reduce this negative effect and improve its biological properties. In turn, SeNPs have a wide range of potential advantages, making them an alternative for areas such as agriculture and food technology. This review focuses on the use of SeNPs and their different applications as antimicrobial agents, growth promoters, crop biofortification, and nutraceuticals in agriculture. In addition, the utilization of SeNPs in the generation of packaging with antioxidant and antimicrobial traits and Se enrichment of animal source foods for human consumption as part of food technology is addressed. Additionally, possible action mechanisms and potential adverse effects are discussed. The concentration, size, and synthesis method of SeNPs are determining factors of their biological properties.

Functional and mechanistic insights into the differential effect of the toxicant ‘Se(IV)’ in the cyanobacterium Anabaena PCC 7120

Selenium, an essential trace element for animals, poses a threat to all forms of life above a threshold concentration. The ubiquitously present cyanobacteria, a major photosynthetic biotic component of aquatic and other ecosystems, are excellent systems to study the effects of environmental toxicants. The molecular changes that led to beneficial or detrimental effects in response to different doses of selenium oxyanion Se(IV) were analyzed in the filamentous cyanobacterium Anabaena PCC 7120. This organism showed no inhibition in growth up to 15mg/L sodium selenite, but above this dose i.e. 20-100mg/L of Se(IV), both growth and photosynthesis were substantially inhibited. Along with the increased accumulation of non-protein thiols, a consistent reduction in levels of ROS was observed at 10mg/mL dose of Se(IV). High dose of Se(IV) (above 20mg/L) enhanced endogenous reactive oxygen species (ROS)/lipid peroxidation, and decreased photosynthetic capability. Treatment with 100mg/L Se(IV) downregulated transcription of several photosynthesis pathways-related genes such as those encoding photosystem I and II proteins, phycobilisome rod-core linker protein, phycocyanobilin, phycoerythrocyanin-associated proteins etc. Interestingly, at a dose range of 10-15mg/L Se(IV), Anabaena showed an increase in PSII photosynthetic yield and electron transport rate (at PSII), suggesting improved photosynthesis. Se was incorporated into the Anabaena cells, and Se-enriched thylakoid membranes showed higher redox conductivity than the thylakoid membranes from untreated cells. Overall, the data supports that modulation of photosynthetic machinery is one of the crucial mechanisms responsible for the dose-dependent contrasting effect of Se(IV) observed in Anabaena.

Effects of Long-Term Supplementation with Aluminum or Selenium on the Activities of Antioxidant Enzymes in Mouse Brain and Liver

The aim of this study was to investigate the effects of aluminum (Al) or selenium (Se) on the “primary” antioxidant defense system enzymes (superoxide dismutase, catalase, and glutathione reductase) in cells of mouse brain and liver after long-term (8-week) exposure to drinking water supplemented with AlCl3 (50 mg or 100 mg Al/L in drinking water) or Na2SeO3 (0.2 mg or 0.4 mg Se/L in drinking water). Results have shown that a high dose of Se increased the activities of superoxide dismutase and catalase in mouse brain and liver. Exposure to a low dose of Se resulted in an increase in catalase activity in mouse brain, but did not show any statistically significant changes in superoxide dismutase activity in both organs. Meanwhile, the administration of both doses of Al caused no changes in activities of these enzymes in mouse brain and liver. The greatest sensitivity to the effect of Al or Se was exhibited by glutathione reductase. Exposure to both doses of Al or Se resulted in statistically significant increase in glutathione reductase activity in both brain and liver. It was concluded that 8-week exposure to Se caused a statistically significant increase in superoxide dismutase, catalase and glutathione reductase activities in mouse brain and/or liver, however, these changes were dependent on the used dose. The exposure to both Al doses caused a statistically significant increase only in glutathione reductase activity of both organs.

Selenium and Salt Interactions in Black Gram (Vigna mungo L): Ion Uptake, Antioxidant Defense System, and Photochemistry Efficiency.

Salinity is a major abiotic stress which limits crop production, especially under rainfed conditions. Selenium (Se), as an important micronutrient, plays a vital role in mitigating detrimental effects of different abiotic stresses. The objective of this research was to examine the effect of Se fertilization on black gram (Vigna mungo) under salt stress. Our results showed that salt stress (100 mM NaCl) in leaves significantly induced oxidative damage and caused a decline in relative water content, chlorophyll (Chl), stomatal conductance (gs), photochemical efficiency (Fv/Fm), sucrose, and reducing sugars. A low dose of Se (1.5 ppm) significantly reduced hydrogen peroxide content, malondialdehyde formation, cell membrane damage, and also improved antioxidative enzyme activities, including superoxide dismutase, catalase, ascorbate peroxidase, glutathione reductase, and glutathione peroxidase under salt stress. Se-treated plants exhibited higher Chl, gs, Fv/Fm, sucrose, and reducing sugars than untreated plants in response to salt stress. In addition, Se application enhanced Se uptake and reduced Na+ uptake, but Cl− remained unaffected. Our results indicated that a low dose of Se effectively alleviated salt damage via inhibition of Na+ uptake and enhanced antioxidant defense resulting in a significant decrease in oxidative damage, and maintained gaseous exchange and PS II function for sucrose and reducing sugars accumulation in black gram.

An Approach to Alleviate the Impact of Drought Stress with Selenium Amendment

Selenium (Se), an essential microelement for humans and animals, has recently gained in importance in the plant systems due to its effects on antioxidative defense system. Several studies demonstrated that low concentrations of Se protect plants against various types of biotic and abiotic stresses. We conducted a pot experiment for 2 months, using Sorghum (Sorghum vulgarea L.), to investigate the protective role of a low dose of Se (20 mg Se/l) against a drought stress. Specifically, we submitted treated and non-treated plants to three different condition of water availability: control condition (100% field capacity), low drought condition (70% field capacity), and high drought condition (35% field capacity) and we measured growth and several physiological traits of these plants. We found that Se treatment stimulates growth and significantly increases the relative water content (RWC) and the chlorophyll content. These findings suggest that Se could alleviate drought stress by promoting growth and regulating water status of sorghum.

Age-Dependent Protective Effect of Selenium against UVA Irradiation in Primary Human Keratinocytes and the Associated DNA Repair Signature.

Few studies have focused on the protective role of selenium (Se) against skin aging and photoaging even though selenoproteins are essential for keratinocyte function and skin development. To the best of our knowledge, the impact of Se supplementation on skin cells from elderly and young donors has not been reported. Therefore, the main objective of our study was to evaluate the effects of Se supplementation on skin keratinocytes at baseline and after exposure to ultraviolet A (UVA) irradiation. Low doses of Se (30 nM) were very potently protective against UVA-induced cytotoxicity in young keratinocytes, whereas the protection efficiency of Se in old keratinocytes required higher concentrations (240 nM). Additionally, the DNA repair ability of the old keratinocytes drastically decreased compared with that of the young keratinocytes at baseline and after the UVA exposure. The Se supplementation significantly enhanced the DNA repair of 8-oxoguanine (8oxoG) only in the keratinocytes isolated from young donors. Therefore, aged keratinocytes have an increased vulnerability to oxidative DNA damage, and the Se needs in the elderly should be considered. Strengthening DNA repair activities with Se supplementation may represent a new strategy to combat aging and skin photoaging.

A Dual Role of Se on Cd Toxicity: Evidences from the Uptake of Cd and Some Essential Elements and the Growth Responses in Paddy Rice

This study was carried out to investigate the effects of selenium (Se) on the uptake and translocation of cadmium (Cd) and essential elements in paddy rice (Oryza sativa L., Shuangyou 998). Selenium could alleviate/aggravate Cd toxicity in paddy rice, which depended on the dosages of Se and/or Cd. When Cd treatment level was as low as 35.6μM, ≤12.7μM Se could inhibit the uptake of Cd in paddy rice and increase the biomass of paddy rice; however, with Cd levels reaching 89-178μM, the addition of Se resulted in increases in Cd uptake and exacerbated the growth of paddy rice. Cd always inhibited the uptake of Se. Cd alone suppressed the uptake of Ca, Mg, Mn, Cu, and Zn; however, Se reversed the decreases in the concentrations of the said elements, suggesting an element regulation mechanism to relieve Cd toxicity. Without Cd in the solution, low doses of Se increased the biomasses of shoots and roots at the expense of the more or less decreases in the concentrations of Ca, Mg, K, Fe, Mn, Cu, and shoot Zn, indicating an antagonistic effect of Se on these cations. The presence of Cd could also reverse these decreases especially at the highest treatment levels for both Se and Cd, also suggesting an element regulation mechanism responsible for the detoxification of high dosages of Se. Consequently, when Se is used to alleviate Cd toxicity, attention must be paid to the Cd pollution extent and doses of Se supplement.

Low doses of selenium specifically stimulate the repair of oxidative DNA damage in LNCaP prostate cancer cells

Epidemiological studies have demonstrated an inverse relationship between selenium (Se) intake and cancer incidence and/or mortality. However, the molecular mechanisms underlying the cancer chemopreventive activity of Se compounds remain largely unknown. The objective of this study was to investigate the effect of low doses of Se on the stimulation of DNA repair systems in response to four different qualities of DNA damage. P53-proficient LNCaP human prostate adenocarcinoma cells were grown either untreated or in the presence of low concentrations of two Se compounds (30° nM sodium selenite, or 10μM selenomethionine) and exposed to UVA, H2O2, methylmethane sulfonate (MMS) or UVC. Cell viability as well as DNA damage induction and repair were evaluated by the alkaline Comet assay. Overall, Se was shown to be a very potent protector against cell toxicity and genotoxicity induced by oxidative stress (UVA or H2O2) but not from the agents that induce other types of deleterious lesions (MMS or UVC). Furthermore, Se-treated cells exhibited increased oxidative DNA repair activity, indicating a novel mechanism of Se action. Therefore, the benefits of Se could be explained by a combination of antioxidant activity, the reduction in DNA damage and the enhancement of oxidative DNA repair capacity.

The Retention of Cadmium and Selenium Influence in Fowl and Chickens of F1 Generation

The retention of cadmium and selenium influence on Cd retention in the muscle, liver and kidneys of hens, chickens and in eggs was studied. Cadmium (Cd) as cadmium chloride (CdCl(2)) and selenium (Se) as sodium selenite (Na(2)SeO(3)) were added to feed at dosages: group 0-control, group 1-20 mg/kg Cd, group 2-30 mg/kg Cd + 4 mg/kg Se. The birds were exposed to Cd for 8 weeks. Cadmium level in hens and cocks was found highest in the kidneys, followed by the liver and muscle. Se supplementation resulted in Cd increase in the muscle tissue and in the reduction of Cd content in the liver and in significant decrease in the kidneys (p < 0.05). A higher Cd level in the yolk and lower in the white was noted in both experimental groups. Nonsignificant increase of Cd in eggs was noted in experimental groups with Se supplementation. Level of cadmium in organs of 7-day-old chicks hatched from Cd-treated hens in both experimental groups was low but the tendency to accumulate preferentially the Cd in the liver and kidneys was recorded. Supplementation of selenium in hens and cocks was not reflected in the decrease of Cd in these two organs of F(1) chickens but was reflected in increase in the muscle. In spite of relatively high Cd levels in the organs of layers no layer-egg-chickens transfer was observed. It was confirm that kidneys and liver are organs more attacked by dietary cadmium than muscle. Supplementation of low dose of Se resulted in decrease of cadmium deposition in analyzed organs.

Selenium increases seed production in Brassica

Selenium (Se) is essential for humans and animals but is not considered to be essential for higher plants. Although researchers have found increases in vegetative growth due to fertiliser Se, there has been no definitive evidence to date of increased reproductive capacity, in terms of seed production and seed viability. The aim of this study was to evaluate seed production and growth responses to a low dose of Se (as sodium selenite, added to solution culture) compared to very low-Se controls in fast-cycling Brassica rapa L. Although there was no change in total biomass, Se treatment was associated with a 43% increase in seed production. The Se-treated Brassica plants had higher total respiratory activity in leaves and flowers, which may have contributed to higher seed production. This study provides additional evidence for a beneficial role for Se in higher plants.

Intratracheal exposure of the guinea pig lung to cadmium and/or selenium: a histological evaluation

Anesthetized male Hartley guinea pigs (350–410 g) ( n=5) received intratracheally, saline; cadmium (Cd) (0.3 mg); selenium (Se) (0.3 or 0.06 mg); or Cd (0.3 mg) with Se (0.06 mg), per animal. Twenty-four hours later, lungs were evaluated. Bronchoalveolar-lavage fluid of Cd- and/or Se-treated animals varied in their total and differential leukocyte percent population from that of saline control ( P<0.05). Cadmium alone or with Se caused high lung to body weight ratios ( P<0.05). High lung wet-weight to dry-weight (W/D) ratios ( P<0.05) suggestive of lung edema, were evident after Cd and/or Se exposure. Histological examination of Cd- and/or Se-exposed lungs revealed leukocytic infiltration. Results demonstrated that separate or concurrent exposure to noxious metal(s) such as Cd and Se provoke lung edema and injury. Low dose of Se which when instilled alone, although did not result in an increased W/D lung ratio, failed to subside concurrently administered Cd-inflicted damage.

Chemical form of selenium greatly affects metal uptake and responses by cultured human lymphocytes.

In this work, possible interference with functional activities of human lymphocytes after in vitro treatment with selenium was examined. Sodium selenite and selenomethionine compounds were tested in parallel, and their capability to inhibit or to increase the antibody production by lymphocytes was investigated. Furthermore, after incubation for 7 d, total cell-associated Se was measured by a fluorimetric method. The in vitro doses of Se employed in this study mainly reflect those measured in blood of individuals with different Se intake. Low doses of Se (0.5-2.0 microM) added either as sodium selenite or selenomethionine did not alter the secretion of antibodies. When Se was added at higher levels, instead, an inhibitory effect was found using selenite, whereas a progressive increase in immunoglobulin production was observed after exposure to selenomethionine. In both cases, modifications were detected at 5 microM (395 micrograms Se/L), and were significant at 10 microM (789 micrograms Se/L). A different trend between the two chemical forms was also observed with regard to Se uptake by cells. Interestingly, both Se uptake and cell sensitivity were influenced by the density of the cells in culture. Our data suggest that the biological effects of Se in mammalian systems are strongly influenced by its chemical form, and caution should be exerted to avoid toxic effects of selenium.

Selenium and Behçet's disease

Behçet's disease is an inflammatory disorder of unknown etiology, characterized by recurrent oral and genital aphthous ulcers, ocular inflammation, and skin lesions of erythema nodosum and acneiform eruptions. Selenium (Se) affects all components of the immune system, i.e., the development and expression of nonspecific, humoral, and cell-mediated responses. In general, a deficiency in Se appears to result in immunosuppression, whereas supplementation with low doses of Se appears to result in augmentation and/or restoration of immunologic functions. In this study, the distribution of Se and IgG, IgM in serum were compared in samples from healthy adult control and Behçet's disease patients. The serum Se levels were measured by AA-30-40 Varian Spectra, and immunoglobulins were measured by immunodiffusion technique. The mean (SD) serum Se level of 54.24 +/- 8.06 ng/mL among Behçet's disease subjects was significantly different (P less than 0.01) from that in the control subjects (90.01 +/- 9.94 ng/mL). We also measured IgG and IgM as 10.01 +/- 2.74 mg/mL and 1.26 +/- 0.29 mg/mL, respectively for patients, and 15.08 +/- 4.73 mg/mL and 1.58 +/- 0.43 mg/mL for controls. The mean values of IgG and IgM for patients were significantly (P less than 0.05) different from the values of controls. It seems, therefore, that a deficiency in selenium impedes the humoral immune response.

Effect of selenium on glutathione metabolism: Induction of γ-glutamylcysteine synthetase and glutathione reductase in the rat liver

The effect of sodium selenite (Na 2SeO 3, Se) on cellular glutathione metabolism was examined, particularly with respect to its ability to alter the activities of γ-glutamylcysteine synthetase and glutathione disulfide (GSSG) reductase. The treatment of rats with Se (5, 10 and 20 μmoles/kg) caused time- and dose-dependent increases in the activities of the synthetase and the reductase in the liver. The activity of γ-glutamylcysteine synthetase, the rate-limiting enzyme of the glutathione (GSH) biosynthesis, was particularly susceptible to Se treatment. The Se-mediated increases in the activities of the above enzymes were inhibited by puromycin and the increases could not be elicited in vitro. Selenium treatment caused time-dependent perturbations in the levels and ratio of GSSG and GSH in the liver. When compared to the control animals, rats treated for 3 hr with 10 and 20 μmoles Se/kg showed increased cellular levels of GSSG; in contrast, 24 hr after Se treatment the concentration of GSH was increased significantly. The activity of γ-glutamyl transpeptidase, which catalyzes the initial reaction in GSH breakdown, was unaltered by Se treatment. Repeated administration of low doses of Se (7.0 μmoles/kg, three times) also increased the activities of the reductase and the synthetase as well as the cellular levels of hepatic GSH and GSSG. It is suggested that the Se-mediated increases in the activities of γ-glutamylcysteine synthetase and GSSG-reductase represent cellular responses to Se-mediated perturbations in the levels and ratio of GSH and GSSG.