Effects of various dietary levels of selenium as selenite or selenomethionine on tissue selenium levels and glutathione peroxidase activity in rats.
TL;DR: The results indicate that the chemical forms of dietary Se can have a marked influence on biological responses, including bioavailability of dietary selenium, as well as in tissues of rats fed SeM rather than selenite.
Abstract: Weanling rats were fed a basal diet or this diet plus 02, 10, 20 or 40 mg/kg selenium (Se) as either selenite or selenomethionine (SeM) Except at the 02 mg/kg Se level, Se accumulated in all tissues at higher levels when SeM was fed than when selenite was given, and the magnitude of difference became more pronounced with increasing levels of dietary Se This was particularly true for muscle and brain Se levels in whole blood, testes, kidney and lungs were not significantly different between rats fed 02 mg/kg Se as selenite or as SeM, but the Se levels in liver, muscle and brain were higher in rats fed SeM Although the tissue Se concentrations differed markedly, there were no differences in the glutathione peroxidase (GPX) activity in tissues of rats fed SeM rather than selenite The percentage of Se associated with GPX was lower in all tissues from rats fed SeM than in those from rats fed selenite These results indicate that the chemical forms of dietary Se can have a marked influence on biological responses, including bioavailability of dietary Se
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TL;DR: According to this two-stage model of the roles of Se in cancer prevention, individuals with nutritionally adequate Se intakes may benefit from Se supplementation and the development of the potential of Se compounds as cancer chemopreventive agents is facilitated.
695 citations
TL;DR: Even though SeMCYS was shown to be the most effective seleno-compound in the reduction of mammary tumours, it may not be the best choice for reduction of colon tumours because several mechanisms have been proposed on the mechanism whereby Se reduces tumours.
Abstract: Selenomethionine (Semet) is the major seleno-compound in cereal grains and enriched yeast whereas Se-methylselenocysteine (SeMCYS) is the major seleno-compound in Se-accumulator plants and some plants of economic importance such as garlic and broccoli exposed to excess Se. Animals can metabolize both Semet and SeMCYS. Epidemiological studies have indicated an inverse relationship between Se intake and the incidence of certain cancers. Blood or plasma levels of Se are usually lower in patients with cancer than those without this disorder, but inconsistent results have been found with toenail-Se values and the incidence of cancer. There have been eight trials with human subjects conducted on the influence of Se on cancer incidence or biomarkers, and except for one, all have shown a positive benefit of Se on cancer reduction or biomarkers of this disorder. This is consistent with about 100 small-animal studies where Se has been shown to reduce the incidence of tumours in most of these trials. Se-enriched yeast is the major form of Se used in trials with human subjects. In the mammary-tumour model, SeMCYS has been shown to be the most effective seleno-compound identified so far in reduction of tumours. Several mechanisms have been proposed on the mechanism whereby Se reduces tumours. Even though SeMCYS was shown to be the most effective seleno-compound in the reduction of mammary tumours, it may not be the most effective seleno-compound for reduction of colon tumours.
578 citations
Cites background from "Effects of various dietary levels o..."
...Feeding diets with Semet to animals as the main Se source will result in greater tissue accumulation of Se than other forms of Se (Whanger & Butler, 1988; Ip & Lisk, 1994)....
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TL;DR: There are several selenocompounds in tissues of plants and animals, and selenocysteine, the predominant selenoamino acid in tissues when inorganic selenium is given to animals, is one of them.
Abstract: There are several selenocompounds in tissues of plants and animals. Selenate is the major inorganic selenocompound found in both animal and plant tissues. Selenocysteine is the predominant selenoamino acid in tissues when inorganic selenium is given to animals. Selenomethionine is the major selenocompound found initially in animals given this selenoamino acid, but is converted with time afterwards to selenocysteine. Selenomethionine is the major selenocompound in cereal grains, grassland legumes and soybeans. Selenomethionine can also be the major selenocompound in selenium enriched yeast, but the amount can vary markedly depending upon the growth conditions. Se-methylselenocysteine is the major selenocompound in selenium enriched plants such as garlic, onions, broccoli florets and sprouts, and wild leeks.
470 citations
Cites background from "Effects of various dietary levels o..."
...Feeding diets with selenomethionine to animals as the main selenium source will result in greater tissue accumulation of selenium than other forms of selenium [68,69]....
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28 Nov 2003
TL;DR: Gel electrophoretic separation of tissue samples from rats labeled in vivo with (75)Se showed the existence of further selenium-containing proteins.
Abstract: ▪ Abstract Mammalian selenium-containing proteins can be divided into three groups: proteins containing nonspecifically incorporated selenium, specific selenium-binding proteins, and specific selenocysteine-containing selenoproteins Selenoproteins with known functions identified so far include five glutathione peroxidases, two deiodinases, several thioredoxin reductases, and selenophosphate synthetase 2 Alternative splicing leads to a greater variety of selenoproteins, as was shown in the cases of a specific sperm nuclei glutathione peroxidase and some thioredoxin reductases Selenoprotein P, selenoprotein W, a 15-kDa selenoprotein, an 18-kDa selenoprotein, and several selenoproteins identified in silico from nucleotide sequence databases were found to contain selenocysteine but their functions are not known Gel electrophoretic separation of tissue samples from rats labeled in vivo with 75Se showed the existence of further selenium-containing proteins
460 citations
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Journal Article•
TL;DR: Procedures are described for measuring protein in solution or after precipitation with acids or other agents, and for the determination of as little as 0.2 gamma of protein.
289,852 citations
TL;DR: Plasma GSHPx, like the erythrocyte enzyme, was found to contain approximately four atoms of selenium per mole of protein and is a glycoprotein, and radioimmunoassay showed that less than 0.13% of the antigenically detectable protein is found in the purified GSHpx from plasma.
399 citations
247 citations
TL;DR: In this article, the results suggest the presence of selenocysteic acid in significant amounts in wheat gluten, seeds and straw from plants grown on soil to which 75Se-selenate had been added.
217 citations
TL;DR: The majority of the selenium in the rat is not contained in the GSH-Px but in other compounds, which differs considerably from tissue to tissue, the highest value being found in the erythrocytes and the smallest in the testes.
Abstract: The selenium content was determined in the adrenals, brain, erythrocytes, femur, hair, heart, kidneys, lungs, muscle, pancreas, plasma, spleen, testes, and thymus of rats, which had been fed a commercial rat diet containing 03 mg Se/kg diet In the plasma, the erythrocytes, and the soluble fraction of the tissues (with the exception of femur and hair) the activity of the glutathione peroxidase (GSH-Px) was measured, using both hydrogen peroxide and t-butyl hydroperoxide as substrates From the masses of the tissues and the values for the selenium content and the GSH-Px activity, the distribution of the element and the enzyme in the body was calculated For selenium the main pools were the muscle and the liver, and for the GSH-Px, the liver and the erythrocytes By comparing the selenium content and the GSH-Px activity the percentage of the tissue selenium, which was bound to the enzyme in the soluble tissue fraction, was estimated This percentage differed considerably from tissue to tissue, the highest value being found in the erythrocytes and the smallest in the testes According to this estimation the majority of the selenium in the rat is not contained in the GSH-Px but in other compounds
190 citations