Human Selenium Research Articles

Optimization of selenium biofortification by liquid fermentation based on 2,4-dichlorophenoxyacetic acid and its effect on nutritional value of Pleurotus ostreatus

Pleurotus ostreatus is one of the most popular edible mushrooms worldwide and has been proposed as a candidate for human selenium (Se) supplementation. The objective of this study is to develop a Se-biofortification method by liquid fermentation and evaluate the effect of 2,4-dichlorophenoxyacetic acid (2,4-D), Na2SeO3 fortification doses and initial pH on P. ostreatus mycelium growth, nutritional value, and mineral accumulation. The optimal growth conditions were identified as 2,4-D 2.00 mg L−1, Na2SeO3 30.65 mg L−1, and initial pH 5.97 by Box-Behnken design. The optimization resulted in the biomass of 15.75 g L−1 and the organic Se content of 594.85 mg kg−1, which was 2.50 and 8.03 times higher than the control group, respectively. In parallel, the contents of polysaccharides, proteins, essential amino acids, major functional components, and several minerals in mycelium were increased to varying degrees. Overall, this study will provide an experimental basis for the use of P. ostreatus mycelium as a good carrier for organic Se enrichment by liquid fermentation and technical support for the industrial development of new Se biofortification methods.

Transcriptome analysis of high- and low-selenium genotypes identifies genes responsible for selenium absorption, translocation, and accumulation.

Selenium is an essential micronutrient the human body requires, which is closely linked to health. Rice, a primary staple food globally, is a major source of human selenium intake. To develop selenium-enriched rice varieties, it is imperative to understand the mechanisms behind selenium's absorption and transport within rice, alongside identifying the key genes involved in selenium uptake, transport, and transformation within the plant. This study conducted transcriptome sequencing on four types of rice materials (two with low-selenium and two with high-selenium contents) across roots, stems, leaves, and panicles to analyze the gene expression differences. Differential gene expression was observed in the various tissues, identifying 5,815, 6,169, 7,609, and 10,223 distinct genes in roots, stems, leaves, and panicles, respectively. To delve into these differentially expressed genes and identify the hub genes linked to selenium contents, weighted gene co-expression network analysis (WGCNA) was performed. Ultimately, 10, 8, 7, and 6 hub genes in the roots, stems, leaves, and panicles, respectively, were identified. The identification of these hub genes substantially aids in advancing our understanding of the molecular mechanisms involved in selenium absorption and transport during the growth of rice.

Effects of Selenate Application on Growth, Nutrient Bioaccumulation, and Bioactive Compounds in Broccoli (Brassica oleracea var. italica L.)

The biofortification of edible crops with selenium (Se) is a common and effective strategy to address inadequate Se intake, which is suffered by millions of people worldwide. However, there is little information regarding the effects of this practice on crops belonging to the important Brassica family. To evaluate the efficacy of foliar Se application on broccoli, four treatments with varying Se concentrations were tested: 0%, 0.05%, 0.10%, and 0.15% (w/v), applied as sodium selenate during the early flowering stage. Although no overall effects on growth and biomass parameters were observed, the results indicate that the lowest Se dose (0.05-Se) was sufficient to notably increase Se concentration in the florets, even after boiling. Based on the increase to 14.2 mg Se kg−1 of dry matter in this broccoli fraction, it was estimated that consuming a 100-gram portion of boiled florets biofortified with 0.05% Se would provide approximately 140 µg of Se, which could be sufficient to potentially improve human selenium status, as previously documented. Moreover, the results obtained underscore how the application of this small dose was also adequate to reduce phytate concentration in the florets and to increase antioxidant and polyphenol concentrations, thereby improving the concentration and bioavailability of other essential nutrients, including Ca, Mg, Fe, and Zn, along with improving its quality as an antioxidant food.

Selenium Status of Southern Africa.

Selenium is an essential trace element that exists in inorganic forms (selenite and selenates) and organic forms (selenoamino acids, seleno peptides, and selenoproteins). Selenium is known to aid in the function of the immune system for populations where human immunodeficiency virus (HIV) is endemic, as studies suggest that a lack of selenium is associated with a higher risk of mortality among those with HIV. In a recent study conducted in Zambia, adults had a median plasma selenium concentration of 0.27 μmol/L (IQR 0.14-0.43). Concentrations consistent with deficiency (<0.63 μmol/L) were found in 83% of adults. With these results, it can be clearly seen that selenium levels in Southern Africa should be investigated to ensure the good health of both livestock and humans. The recommended selenium dietary requirement of most domesticated livestock is 0.3 mg Se/kg, and in humans above 19 years, anRDA (recommended daily allowance) of 55 mcg Se/per dayisis recommended, but most of the research findings of Southern African countries have recorded low levels. With research findings showing alarming low levels of selenium in soils, humans, and raw feed materials in Southern Africa, further research will be vital in answering questions on how best to improve the selenium status of Southern African soils and plants for livestock and humans to attain sufficient quantities.

Selenium enrichment and quality improvement of Origanum vulgare plants grown under in vitro condition with salicylic acid

One of the important sources of human selenium intake is vegetables, so increasing of selenium in edible parts of plants, biofortification, provides an effective approach to reduce selenium deficiency. Origanum vulgare L. is an important medicinal plant which is also used as a valuable spice. The present study was done to evaluate the ability of selenium accumulation of micropropagated O. vulgare under sodium selenate and/or salicylic acid treatment. Micropropagation of O. vulgare was done from shoot-tips as explants on modified Murashige & Skoog (MS) medium. After 1 month, rooted plantlets were transferred to modified Murashige & Skoog solidified medium containing sodium selenate (0, 25 and 50 µM) and/or salicylic acid (0 and 100 mgL−1). After 4 wk, growth, selenium accumulation, biochemical parameters and oxidative stress indicators were determined. The results showed that the plantlets were able to accumulate 16.1 µg g−1 DW and 28.27 µg g−1 DW selenium in shoots at 25 and 50 µM selenate sodium concentrations respectively. Both concentrations of selenium increased shoot dry weight, length of shoot and root, soluble sugars and total protein content, peroxidase and superoxide dismutase activity. On the contrary, malondialdehyde content decreased under selenium treatment. It was found that by increasing selenium concentration the content of total protein, H2O2 and antioxidant enzymes activity increased significantly. Application of salicylic acid in combination with selenium improved growth but did not affect on selenium accumulation. The obtained results can be considered as the first report of biofortification of O. vulgare under tissue culture technique.

Effects of Pyrolysis Temperature and Acid-Base Pre-Treatment on the Synthesis of Biochar-Based Slow-Release Selenium Fertilizer and Its Release in Soil.

Plant-derived selenium is an important source of selenium (Se) for humans, which, however, has been restricted by a low content of Se in soil. Traditional Se fertilizers have tended to result in low selenium utilization. Thus, it was necessary to develop a new slow-release material to control Se fertilizer release. In this study, biochar pyrolyzed at 300 °C and 800 °C was cross-linked with polyethyleneimine (PEI) after being treated with HNO3 or NaOH (which were labeled Acid-W300, Acid-W800, Alkali-W300, and Alkali-W800). The results showed that the maximum adsorption capacities of Acid-W300, Alkali-W300, Acid-W800, and Alkali-W800 were 329.16 mg/g, 321.93 mg/g, 315.04 mg/g, and 344.33 mg/g, respectively. Among them, Acid-W800 and Alkali-W800 were mainly imine- and amide-bonded with SO32-, while Acid-W300 and Alkali-W300 were loaded with SO32- by forming the C-Se bonding as well as through imine- and amide-bonding. The release of four biochar-based selenium fertilizers in the red soil and brown soil extracts conformed to the pseudo-second-order kinetic model. The release rate and release amount of four biochar-based selenium fertilizers in the red soil extract were higher than those in the brown soil extract. Alkali-W800-Se had a higher proportion of Se-exchangeable release, accounting for 87.5% of the total loaded selenium, while Acid-W300-Se had the lowest proportion at 62.2%. However, the Se releases of Alkali-W800-Se were more than 42.49% and 37.67% of the total Se-loading capacity during 5 days of continuous red soil extraction and brown soil extraction, respectively. Acid-W300-Se released less than 20% of the total Se-loading capacity. Thus, Acid-W300-Se was the recommended slow-release Se fertilizer in red soil and brown soil.

Selenium Biofortification: Strategies, Progress and Challenges

Selenium (Se) is an essential trace element for humans and animals. Its necessity for plants is still under examination. Due to the contradictory nature of Se and its significance, it has received much interest in recent years. Se deficiency can be harmful to humans, yet almost a billion people are deficient. Its deficiency has been associated with cancers, impairment of organs, and a number of other ailments. The biofortification of plants and livestock is a guaranteed practice to increase human selenium consumption. Strategies such as foliar spraying, the direct application of Se in plants and Se feed, and injections in livestock have been employed. Se biofortification has been shown to have additional beneficial effects in plants and livestock. In plants, it has been reported to mitigate different types of stress and increase yield. In animal biofortification, Se has been shown to reduce the detrimental effects of ailments and promote healthy growth. Se biofortification, nevertheless, confronts a number of difficulties. For instance, the bulk of biofortified products must be prepared before consumption, lowering the Se concentration. The objective of this review is to convey the current understanding of the Se biofortification of plants and animals, as well as its difficulties, taking into account both the detrimental consequences of Se deficiency and benefits of Se biofortification.

A Capillary Zone Electrophoresis Method for Selenite Detection in Culture Media for Total Selenium Determination in Yeast Cells

Selenium enriched yeast is the most prevalent source of organic selenium for humans and animals. In this study, an effective capillary zone electrophoresis method was established to quantify total selenium in yeast biomass by measuring selenite level in post incubated culture media. The detection of selenite could be achieved within 7.9 min under the condition of a mixture buffer of 85 mM Na2HPO4 and 0.5 mM CTAB (pH 9.37), –5 kV separation voltage with 1.0 psi × 30 s injection at 200 nm. The range of calibration curve linearity of the standard was from 5 to 300 mg/L (r2 = 0.99998), and the recovery was 102.4%. Owing to the ease of sample collection and simple detection, this method is convenient for the evaluation of total selenium accumulated in yeast cell biomass and helps to guide the production of selenium enriched yeast.

Biogenic production of selenocysteine by Enterococcus faecium ABMC-05: an indigenous lactic acid bacterium from fermented Mexican beverage

Lactic acid bacteria have been studied for their ability to accumulate inorganic selenium, which is reduced to its elemental form or could be integrated into selenoproteins in the form of selenocysteine. This ability to produce bioavailable organic selenium for humans is an advantage that could be exploited in the production of functional foods. In this work, Enterococcus faecium ABMC-05 isolated from a traditional Mexican beverage (tepache) and with NCBI entry number OL413240 was used. Microorganism selenization was performed after the determination of minimal inhibitory concentration of Na2SeO3 (184 mg/L), which was calculated using the graphical method of Talmadge and Fitch. The selenium concentration of accumulated selenium was calculated by inductively coupled plasma optical emission spectroscopy (ICP-OES). The concentration of selenium at 48 h of fermentation was 39.92 mg/L, which represented 23.8% of selenium at medium. This value was consistent with those reported for other lactic acid bacteria. Finally, it was determined the selenocysteine presence in biomass recovery after fermentation using RP-HPLC technique. With these results it was confirmed the biogenic production of selenocysteine by Enterococcus faecium ABMC-05 using an inorganic source.

Linkages between soil, crop, livestock, and human selenium status in Sub-Saharan Africa: a scoping review.

Selenium (Se) is essential for human health, however, data on population Se status and agriculture-nutrition-health linkages are limited in sub-Saharan Africa (SSA). The scoping review aims to identify linkages between Se in soils/crops, dietary Se intakes, and livestock and human Se status in SSA. Online databases, organisational websites and grey literature were used to identify articles. Articles were screened at title, abstract and full text levels using eligibility criteria. The search yielded 166 articles from which 112 were excluded during abstract screening and 54 full text articles were assessed for eligibility. The scoping review included 34 primary studies published between 1984 and 2021. The studies covered Se concentrations in soils (n = 7), crops (n = 9), animal tissues (n = 2), livestock (n = 3), and human Se status (n = 15). The evidence showed that soil/crop Se concentrations affected Se concentration in dietary sources, dietary Se intake and biomarkers of Se status. Soil types are a primary driver of human Se status and crop Se concentration correlates positively with biomarkers of Se dietary status. Although data sets of Se concentrations exist across the food system in SSA, there is limited evidence on linkages across the agriculture-nutrition nexus. Extensive research on Se linkages across the food chain is warranted.

Selenium as an important factor in various disease states - a review.

Selenium (Se) is an element that has a pro-health effect on humans and animals. However, both the deficiency of this element and its excess may prove harmful to the body depending on the chemical form of the selenium, the duration of supplementation, and the human health condition. Many data indicate insufficient coverage of the demand for selenium in humans and animals due to its low content in soils and food products. A balance in the physiological process of the body can be achieved via the proper percentage of organically active minerals in the feed of animals as well as human beings. Selenium is a trace mineral of great importance to the body, required for the maintenance of a variety of its processes; primarily, selenium maintains immune endocrine, metabolic, and cellular homeostasis. Recently, this element has been emerging as a most promising treatment option for various disorders. Therefore, research based on Se has been increasing in recent times. The present review is designed to provide up-to-date information related to Se and its different forms as well as its effects on health.

Discriminative Long-Distance Transport of Selenate and Selenite Triggers Glutathione Oxidation in Specific Subcellular Compartments of Root and Shoot Cells in Arabidopsis.

Selenium is an essential trace element required for seleno-protein synthesis in many eukaryotic cells excluding higher plants. However, a substantial fraction of organically bound selenide in human nutrition is directly or indirectly derived from plants, which assimilate inorganic selenium into organic seleno-compounds. In humans, selenium deficiency is associated with several health disorders Despite its importance for human health, selenium assimilation and metabolism is barely understood in plants. Here, we analyzed the impact of the two dominant forms of soil-available selenium, selenite and selenate, on plant development and selenium partitioning in plants. We found that the reference plant Arabidopsis thaliana discriminated between selenate and selenite application. In contrast to selenite, selenate was predominantly deposited in leaves. This explicit deposition of selenate caused chlorosis and impaired plant morphology, which was not observed upon selenite application. However, only selenate triggered the accumulation of the macronutrient sulfur, the sister element of selenium in the oxygen group. To understand the oxidation state-specific toxicity mechanisms for selenium in plants, we quantified the impact of selenate and selenite on the redox environment in the plastids and the cytosol in a time-resolved manner. Surprisingly, we found that selenite first caused the oxidation of the plastid-localized glutathione pool and had a marginal impact on the redox state of the cytosolic glutathione pool, specifically in roots. In contrast, selenate application caused more vigorous oxidation of the cytosolic glutathione pool but also impaired the plastidic redox environment. In agreement with the predominant deposition in leaves, the selenate-induced oxidation of both glutathione pools was more pronounced in leaves than in roots. Our results demonstrate that Se-species dependent differences in Se partitioning substantially contribute to whole plant Se toxicity and that these Se species have subcellular compartment-specific impacts on the glutathione redox buffer that correlate with toxicity symptoms.

Selenium Concentration in Cattle Serum and Fodder from Two Areas in Ethiopia with Contrasting Human Selenium Concentration.

Selenium (Se) is an essential mineral for livestock health and productivity. In cattle, Se deficiency is associated with delayed conception, growth retardation, and increased morbidity and mortality. We conducted a survey of cattle serum (n = 224) and feed (n = 81) samples from two areas with contrasting human and cereal grain Se concentration in Ethiopia. The fodder samples include stover, straw, hay and pasture grass. Se concentration of the samples were measured using inductively coupled plasma-mass spectrometry. Serum Se concentration ranged from 14.9 to 167.8 μg L-1 (median, 41.4 μg L-1). Cattle from East Amhara had significantly greater serum Se concentration compared to cattle from West Amhara (median: 68.4 μg L-1 vs 25.7 μg L-1; p < 0.001). Overall, 79.8% of cattle had Se deficiency (<81 μg L-1). All of the cattle from West Amhara were Se deficient compared with 62.5% of those from East Amhara. State of lactation of cows or age of cattle was not associated with serum Se concentration. The Se concentrations of feed samples ranged from 0.05 to 269.3 μg kg-1. Feed samples from East Amhara had greater Se concentration than samples from West Amhara. Cow serum and cattle feed Se concentrations showed strong spatially correlated variation, with a strong trend from East to West Amhara. This study shows that cattle Se deficiency is likely to be highly prevalent in Ethiopia, which will negatively affect the health and productivity of livestock. The deficiency appears to be geographical dependent. More extensive surveys to map Se concentration in soil-feed-livestock-human cycle are required in Ethiopia and elsewhere.

Selenium in human and animal nutrition and need for selenium fertilization of crops

Selenium is an essential micronutrient for humans and animals, required to increase immunity, protect cells from free radical damage and inflammation, and support a healthy metabolism. The typical manifestations of selenium deficiency in humans are loss of appetite, fatigue after even mild exercise, cardiac arrhythmia and palpitations, cardiac insufficiency, cardiomegaly, and congestive heart failure, swelling in the joints of arms and legs in children aged 5–13 years resulting in structural shortening of the fingers and long bones resulting in growth retardation and stunting. Clinical signs of selenium deficiency in cattle include mastitis, perinatal death and abortions, suboptimal fertility in adult cattle and suboptimal milk production, acute nutritional muscular dystrophy in young calves, sudden collapse or death of calves within 2–3 days of birth, stiff-legged gait, weakness and inability to stand or walk in young calves.Being a micronutrient for humans and animals, the margin between deficiency and toxicity of selenium are small and selenium supplementation has to be carefully planned. Agronomic biofortification by fertilizing crops on selenium deficient soils is the safest way and has been successfully tried in China and Finland. It is now practised in Australia and several other countries. However, the research work on selenium in soils, plants, animals and humans is of recent origin in India and needs utmost attention and priority considering its importance in the food chain.

Role of Selenium in Plants, Animals, and Humans

Role of Selenium in Plants, Animals, and Humans

Stakeholder interpretation of probabilistic representations of uncertainty in spatial information: an example on the nutritional quality of staple crops

Spatial information, inferred from samples, is needed for decision-making, but is uncertain. One way to convey uncertain information is with probabilities (e.g. that a value falls below a critical threshold). We examined how different professional groups (agricultural scientists or health and nutrition experts) interpret information, presented this way, when making a decision about interventions to address human selenium (Se) deficiency. The information provided was a map, either of the probability that Se concentration in local staple grain falls below a nutritionally-significant threshold (negative framing) or of the probability that grain Se concentration is above the threshold (positive framing). There was evidence for an effect of professional group and of framing on the decision process. Negative framing led to more conservative decisions; intervention was recommended at a smaller probability that the grain Se is inadequate than if the question were framed positively, and the decisions were more comparable between professional groups under negative framing. Our results show the importance of framing in probabilistic presentations of uncertainty, and of the background of the interpreter. Our experimental approach could be used to elicit threshold probabilities which represent the preferences of stakeholder communities to support them in the interpretation of uncertain information.

Correlation of Selenium Deficiency with Anthropometric Parameters among Primary School Children in Southwestern Nigeria

Background: Selenium is of fundamental importance to health, being an essential trace element involved in many immunological, endocrine, and antioxidant pathways. Its deficiency is associated with growth failure, poor immune function, cognitive decline and increased risk of morbidity and mortality especially among school aged children. The study aims at determining the serum level of selenium among primary school pupils in Ogbomoso North Local Government Area and its correlations with their socioeconomic characteristics and the anthropometric indices. Method : Children aged 6 to 12 years old were recruited from registered public and private primary schools. A semi-structured questionnaire designed for the study was used to obtain relevant data. Serum selenium levels was estimated using Human Selenium Binding Protein. Chi-square test of independence was used to examine the association between selenium levels and each of socio-demographic variables and anthropometric indices while Pearson moment correlation was used to determine the correlation between selenium levels and socio-demographic characteristics and anthropometric indices of the study population. Results : The mean age of the subjects was 8.35 ± 1.61 years. Majority (86.7%) of the subjects were from middle and high socio-economic classes. The prevalence of stunting, underweight, overweight and obesity was found to be 8.8%, 4.3%, 1.8% and 2.0% respectively. The mean serum selenium concentration was 0.51 ± 0.30ng/ml while mean serum albumin was 40.4 ± 8.13 g/l. Selenium deficiency was 36.5% and low serum protein and albumin was found in 15.1% and 27% of the study population respectively. Serum selenium level was significantly associated with age, family size and gender. There was a negative correlation between age group, family size and serum selenium levels while a positive correlation exist between socio-economic class and selenium levels. Weight-for age and height-for-age has a positive correlation with selenium levels while stunting and selenium levels were negatively correlated. Conclusion: Prevalence of selenium deficiency is high among subjects and it is an important public health challenge in the country. Socio-demographic characteristics like age, family size, gender and socio-economic class are significantly associated with selenium status of the school children. Selenium deficiency was significantly related to the nutritional status of the study population.

Determination of Selenomethionine, Selenocystine, and Methylselenocysteine in Egg Sample by High Performance Liquid Chromatography—Inductively Coupled Plasma Mass Spectrometry

The deficiency of selenium in dietary is recognized as a global problem. Eggs, as one of the most widely consumed food products, were readily enriched with selenium and became an important intake source of selenium for humans. In order to better understand the speciation and bioaccessibility of selenium in eggs, a simple and reliable approach that could be easily used in a routine laboratory was attempted to develop for analyzing selenium species. Three of organic selenium species (selenocystine, methylselenocysteine, and selenomethionine) in liquid whole egg were completely released by enzymatic hydrolysis and detected by high performance liquid chromatography in combination with inductively coupled plasma mass spectrometry (HPLC-ICP-MS). All the parameters in enzymatic hydrolysis and separation procedures were optimized. The effect of matrix in analysis was critically evaluated by standard addition calibrations and external calibrations. Under the optimal conditions, the spike recoveries of selenium species at 0.1–0.4 μg g−1 spike levels all exceeded 80%. This method was successfully applied to the determination of selenium species in fresh egg and cooked eggs.

Biliary excretion of arsenic by human HepaRG cells is stimulated by selenide and mediated by the multidrug resistance protein 2 (MRP2/ABCC2)

Millions of people worldwide are exposed to unacceptable levels of arsenic, a proven human carcinogen, in drinking water. In animal models, arsenic and selenium are mutually protective through formation and biliary excretion of seleno-bis (S-glutathionyl) arsinium ion [(GS)2AsSe]−. Selenium-deficient humans living in arsenic-endemic regions are at increased risk of arsenic-induced diseases, and may benefit from selenium supplementation. The influence of selenium on human arsenic hepatobiliary transport has not been studied using optimal human models. HepaRG cells, a surrogate for primary human hepatocytes, were used to investigate selenium (selenite, selenide, selenomethionine, and methylselenocysteine) effects on arsenic hepatobiliary transport. Arsenite + selenite and arsenite + selenide at different molar ratios revealed mutual toxicity antagonism, with the latter being higher. Significant levels of arsenic biliary excretion were detected with a biliary excretion index (BEI) of 14 ± 8%, which was stimulated to 32 ± 7% by selenide. Consistent with the formation and biliary efflux of [(GS)2AsSe]−, arsenite increased the BEI of selenide from 0% to 24 ± 5%. Arsenic biliary excretion was lost in the presence of selenite, selenomethionine, and methylselenocysteine. Sinusoidal export of arsenic was stimulated ∼1.6-fold by methylselenocysteine, but unchanged by other selenium forms. Arsenic canalicular and sinusoidal transport (±selenide) was temperature- and GSH-dependent and inhibited by MK571. Knockdown experiments revealed that multidrug resistance protein 2 (MRP2/ABCC2) accounted for all detectable biliary efflux of arsenic (±selenide). Overall, the chemical form of selenium and human MRP2 strongly influenced arsenic hepatobiliary transport, information critical for human selenium supplementation in arsenic-endemic regions.

Отравление селеном и его соединениями в промышленности и быту

Селен — химический элемент с атомным номером 34. Обозначается символом Se. Селен — необходимый для жизни микроэлемент. Обладает выраженными антиоксидантными и антиканцерогенными свойствами. Принимает участие во многих процессах в организме, чем обеспечивает функционирование иммунной и эндокринной систем. Влияет на физическое и умственное развитие у детей. Пища является основным источником селена для человека. В промышленности селен получают как побочный продукт переработки меди. Его используют в электронных полупроводниках, как обесцвечивающее вещество для керамики и стекла, как вулканизирующее вещество в производстве шин. Селен применяется в фармакологии, как антиканцерогенное средство. Соли селена легко всасываются слизистыми оболочками желудочно-кишечного тракта. В крови селен связывается с гемоглобином, образуется селенгемоглобин, в результате возникает гемическая гипоксия. В тканях селен вытесняет серу из серосодержащих аминокислот, нарушаются окислительно-восстановительные процессы. Селениты как активные антиоксиданты уменьшают активность глутатионпероксидазы и глутатионредуктазы и блокируют метаболизм глутатиона. Замена S-S связей селенотрисульфидными комплексами приводит к изменению третичной структуры белков и нарушает их функцию. В больших дозах селен вызывает отравление — селенизм. Для человека токсическая доза селена составляет 5 мг. Обладает политропным действием с преимущественным поражением печени, почек и центральной нервной системы. Острые тяжелые ингаляционные отравления протекают бурно и фульминантно. После вдыхания паров селена в больших концентрациях наблюдается потеря сознания и состояние коллапса. Характерным является чесночный запах изо рта. При ингаляционном пути поступления селена в концентрации 1–4 мкг/л описана клиника раздражения верхних дыхательных путей с развитием токсического отека легких и пневмонии. Наблюдаются явления гастроэнтерита, энцефаломиелита, анорексии, влажный и себорейный дерматит. Хроническая интоксикация селеном напоминает мышьяковую интоксикацию. Характерно снижение массы тела, апатия, усталость, мигрень, головокружение, тошнота, рвота, диарея, тяжесть в области правого подреберья, хронические бронхиты, гипохромная анемия; также выпадение волос, белые горизонтальные полосы на ногтях рук, паронихия, раздражительность, гиперрефлексия, чесночный запах при дыхании и металлический привкус во рту; болезненная чувствительность мышц, тремор, головокружение и покраснение лица. Лечение включает в себя введение антидотов, промывание слизистых оболочек, противошоковые мероприятия и симптоматическую терапию.