Selenium altered regulation of heme biosynthesis in chick embryos

Selenium Deficiency as a Risk Factor for Development of Anemia

Anemia is an important public health problem worldwide. Although iron (Fe) deficiency is considered the main factor in the pathogenesis of anemia, only 40-60% of anemia cases are responsive to Fe supplementation. Considerable data exist that other micronutrient deficiencies, such as selenium (Se), could be possible causes of anemia. The issue of Se deficiency as a risk factor for the development of anemia is of particular interest to our country since the Balkan region is known by a low Se content of soils. The aim of the study was to examine the contemporary conception of the influence of Se deficiency on the development of anemia by a review of the scientific literature. Most animal studies have shown a significant relation between Se deficiency and anemia, but one study indicates that there is no impact of Se deficiency on the hematological parameters. Associations of low serum Se with anemia have been found in a number of human studies including subjects of various age groups and pathological conditions. Three possible biological mechanisms have been suggested for the involvement of Se deficiency in the development of anemia: increased oxidative stress, modulation of inflammation through induction of interleukin-6, and increased expression of heme oxygenase-1. A more categorical clarification of the relationships between Se deficiency and development of anemia is needed with respect to appropriate trace element supplementation in cases of anemia with insufficient or absent therapeutic response to Fe treatment.

Selenium effects on gallium arsenide induced biochemical and immunotoxicological changes in rats

The influence of selenium (6.3 and 12.6 micromol/kg, intraperitoneally) on the disposition of gallium and arsenic and a few gallium arsenide (GaAs) sensitive biochemical variables was studied in male rats. Concomitant administration of Se and GaAs (70 micromol/kg, orally, 5 days a week for 4 weeks) significantly prevented the accumulation of arsenic while, the gallium concentration reduced moderately in the soft organs. The biochemical (haematopoietic and liver) and immunological variables however, responded less favorably to selenium administration. Most of the protection was however observed with the dose of 12.6 micromol rather than at 6.3 micromol. The results thus suggest a few beneficial effects of selenium in preventing the appearance of signs of GaAs toxicity like preventing inhibition of blood delta-aminolevulinic acid dehydratase (ALAD), hepatic malondialdehyde (MDA) formation and the accumulation of gallium and arsenic concentration.

Effect of organic forms of selenium on delta-aminolevulinate dehydratase from liver, kidney, and brain of adult rats

The inhibitory effect of various forms of organic selenium compounds and of diphenyl ditelluride (PhTe)2 on delta-aminolevulinate dehydratase (delta-ALA-D) from liver, kidney, and brain of rats was investigated because it has been reported that organocalcogens catalyze the oxidation of thiols. Diphenyl diselenide (PhSe)2, rho-chloro-diphenyl diselenide (rho ClPhSe)2, propyl-2-2-diphenyl diselenide, and propyl-2-methoxy-2-phenyl selenide inhibited delta-ALA-D and the IC50 ranged from 2 to 32 microM depending on the selenium compound and whether it was preincubated with the enzyme. (rho ClPhSe)2 was the most potent inhibitor of delta-ALA-D, and preincubation increased the inhibitory potency of all the tested compounds. Inorganic selenium compounds (sodium selenite, Na2SeO3 and selenium dioxide, SeO2) inhibited delta-ALA-D, and the potency of SeO2 was greater than that of (rho ClPhSe)2. Diphenyl ditelluride (PhTe)2 also inhibited delta-ALA-D but with relatively lower potency than that of organic and inorganic selenium compounds. The inhibitory effect of propyl-2-2-diphenyl diselenide and propyl-2-methoxy-2-phenyl selenide seems to be mediated by (PhSe)2 since the compounds decomposed rapidly to (PhSe)2 in aqueous medium. The inhibitory action of selenium forms on delta-ALA-D from liver, kidney, and brain was antagonized by sulfhydryl protecting agents (dithiotreitol and reduced glutathione). The effects of organic selenium compounds on delta-ALA-D were related to the stability of the Se-Se (or Se-C) bond because the compound methyl-diphenyl diselenide (which possesses the most stable Se-C-Se bond) did not inhibit the enzyme. The inhibitory action of (PhSe)2 was not related to the formation of oxyradicals in the medium since superoxide dismutase and catalase did not affect the inhibition of delta-ALA-D by (PhSe)2. delta-ALA-D from cucumber leaves was not inhibited by selenium or tellurium compounds which suggests that these compounds act directly on the B or beta-site of the animal enzyme. These results suggest that delta-ALA-D from liver, kidney, and brain is a potential molecular target for the toxic effect of organic forms of selenium and tellurium.

Inhibition of lipid peroxidation by selenium in chick embryos

Toxic doses of Selenium (Se) (12.5 and 37.5 micro moles/Kg egg wt.) administered to 14 day old chick embryos reduced the level of lipid peroxides (LPO) significantly both in hepatic and brain tissues. However, the LPO formation was inhibited maximally at early hours after exposure (3 h and 6 h) and it was gradually increased thereafter to normal levels by 48 h. Further, the effect of Se on some of the antioxidant enzymes like glutathione peroxidase (GPx), glutathione transferase (GST), glutathione reductase (GR), superoxide dismutase (SOD) and catalase were studied. In hepatic tissues GPx, GST and SOD activities were increased at 6 h post treatment with no change in the activities of GR and catalase. However, at 48 h GST and catalase activities were found to be increased, while GPx, GR and SOD activities were not affected. In brain at 6 h increase in the activities of GPx, GST, GR and SOD and no change of catalase were observed. At 6 h glutathione (GSH) levels were reduced in both hepatic and brain tissues. Our results suggest that the elevated levels of antioxidant enzymes at early hours were successful in bringing LPO levels back to normal.