Selenium-mediated biochemical changes in Japanese quails : Tissue uptake and distribution of injected(75)selenium labeled sodium selenite in relation to dietary selenium status.
TL;DR: The tissue uptake and distribution of injected [75Se]-sodium selenite as a variance with time and as influenced by dietary selenium status was followed in the tissues of Japanese quails.
Abstract: The tissue uptake and distribution of injected [(75)Se]-sodium selenite as a variance with time and as influenced by dietary selenium status was followed in the tissues of Japanese quails,Coturnix coturnix japonica. Quails maintained on a low selenium semipurified (basal) diet and basal diets supplemented with 0.2 and 2.0 ppm selenium as sodium selenite were injected intraperitonially with(75)Se as sodium selenite (2.8 microcuries). The injected(75)Se was monitored in blood, liver, kidney, heart, and testis at 24, 72, and 144 h after injection. Maximal uptake of the injected(75)Se was observed in tissues of quails maintained on basal diet. The uptake of(75)Se in tissues in general was determined by the dietary Se status. Among the organs studied, kidney had the maximal level of(75)Se, 0.2 ppm (μg/g wet tissue) followed by liver, testis, and heart, but testis had the maximal level when the level per milligram of protein was considered, about 3.0 ng/mg protein, followed by liver, kidney, and heart. About 10-20% of the tissue(75)Se was located in the mitochondria and 50-60% in the post-mitochondrial supernatant fractions in all dietary Se levels. Significant incorporation of(75)Se in the mitochondrial membrane was observed. The percent distribution ratio between the membrane and matrix fractions of the mitochondria remained constant at all dietary Se levels which, in liver was 65∶35, in kidney 55∶45, and in testis 75∶25. However, in heart mitochondria, the distribution of(75)Se between membrane and matrix varied with dietary Se status, the ratio being 82∶18 in the basal group, and 72∶28 and 41∶59 in the 0.2 and 2.0 ppm Se-supplemented groups, respectively. This is indicative of a preferential uptake of(75)Se in the mitochondrial membrane in conditions of deficiency. About 40-60% of the mitochondrial membrane-associated(75)Se was released upon Triton treatment in all the organs. Of the membrane-bound(75)Se, about 10-15% was acid-labile in liver and kidney and 25% in the heart tissue. Possibilities of tissue specific roles, especially in the heart mitochondrial membrane-related processes, are indicated for selenium.
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TL;DR: Electron microscopic observations revealed structural changes such as loss of cristae with proliferative and degenerative changes of the mitochondria in Se deficiency and involvement of Se in maintaining structure and functional efficiency of mitochondria is evident from the present study.
Abstract: Selenium (Se) deficiency in the experimental models, Coturnix coturnix japonica and Corcyra cephalonica, resulted in impaired mitochondrial substrate oxidations and lowered thiol levels. Studies with respiratory inhibitors confirmed reduced mitochondrial electron transport enzyme activities, especially at cytochrome c oxidase (COX), the terminal segment. Enhanced mitochondrial lipid peroxidation in Se deficiency was more pronounced in the heart tissue of the quail compared to other tissues. Glutathione peroxidase (GSH-Px) activity toward H2O2 and cumene hydroperoxide were generally low in the insect muscle tissue and activity toward H2O2 was maximal in the quail heart mitochondria that was not very sensitive to Se status. Lowered COX activity in Se deficiency was more directly correlated with the increased level of lipid peroxidation than with the GSH-Px activity measured, suggestive of Se mediated protective mechanisms independent of GSH-Px. Electron microscopic observations revealed structural changes such as loss of cristae with proliferative and degenerative changes of the mitochondria in Se deficiency. Involvement of Se in maintaining structure and functional efficiency of mitochondria is evident from the present study.
35 citations
TL;DR: The results including the differential response of GR activity to Se or mimosine supplementation are reflective of an effective reductive environment in Se groups and increased turnover of GSH in the presence of Mimosine.
Abstract: Actaptive alterations in glutathione (GSH) metabolism were studied during oxidative stress induced by selenium (Se) deficiency in germinating seedlings ofTrigonella foenum- graecum grown for 72 h and the response to supplementation individually of Se or mimosine was explored. Growth enhancement with improved mitochondrial efficiency was elicited by supplementation of Se at 0.5-0.75 ppm or mimosine at 0.1-0.2 mM. Total thiol and protein levels of mitochondrial and soluble fractions, in general, did not vary significantly with supplementation of either Se or mimosine except that the mitochondrial protein levels in mimosine groups (0.1-0.2 mM) decreased by 20–30%. Mitochondrial glutathione peroxidase (GSH-Px) increased by twofold in activity toward H2O2, cumene hydroperoxide (CHP), and t-butyl hydroperoxide (tBHP) in Se groups, and by 50–60% increase toward H2O2 and CHP but by a twofold enhancement in enzyme activity with tBHP in mimosine groups. Soluble GSH-Px activity increased by 30–40% only in mimosine groups and remained unaltered in Se groups. Glutathione S-transferase activity (GST) in the soluble fraction of both Se and mimosine groups increased dramatically by fivefold to sixfold. Distinct differences were noted in the response of the stressed seedlings toward exposure to Se or mimosine and included a decline in glutathione reductase (GR) activity by 50–60% in both mitochondria and soluble fractions of Se groups and an increase in GR activity of the mitochondria by twofold and of the soluble enzyme activity by 30% in the mimosine groups. Mimosine exposure resulted in a dose-dependent decrease in the γ-glutamyl transpeptidase levels, but, in contrast, a significant enhancement by 50% was noted in the Se group at 0.75 ppm. The results including the differential response of GR activity to Se or mimosine supplementation are reflective of an effective reductive environment in Se groups and increased turnover of GSH in the presence of mimosine.
23 citations
Cites background from "Selenium-mediated biochemical chang..."
...The severe symptoms of oxidative stress prevalent in Se deficiency, well studied in animal systems (13-15), are coincidental with altered glutathione metabolism, including elevation of glutathione S-transferase (GST), a nonselenoenzyme, involved in detoxication mechanisms....
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TL;DR: It is demonstrated for the first time that mimosine, a naturally occuring toxic amino acid, could be a beneficial growth factor in concentrations between 0.1 and 0.2 mM.
Abstract: Oxidative stress during selenium (Se) deficiency in the seedlings ofTrigonella foenum-graecum grown for 72 h was investigated and the response to supplemented levels of Se (0.5-1 ppm) and mimosine (0.05-1 mM) was evaluated. Beneficial effects of Se was maximal at 0.75 ppm. Mimosine, a toxic amino acid, was also found to be beneficial to the growth of the seedlings exposed up to 0.2 mM. When compared to the stressed seedlings, mitochondrial oxygen uptake from seedlings of Se (0.75 ppm) group and mimosine (0.2 mM) group exhibited threefold enhancement in state 3 respiration rate and a controlled state 4 rate, with respiratory control ratios of 5–8. Upon supplementation at the optimal levels, Superoxide dismutase (SOD) activities were enhanced fourfold with Se and eightfold with mimosine in the mitochondria. The soluble activity in mimosine groups increased twofold, but only by 75% in Se groups. Peroxidase activity registered a significant increase by threefold in mitochondria and fourfold in soluble fraction in both Se and mimosine groups. Exposure to Se or mimosine exhibited a differential response in the mitochondrial catalase and ascorbate peroxidase (Asc-Px) activities. In the Se groups, both catalase and Asc-Px in mitochondria decreased by 50–60%, which was contrasted by 60% increase in Asc-Px activity and 40% in catalase activity in mimosine groups. Supplementation with either Se or mimosine evoked similar responses of increases with respect to soluble catalase by twofold to threefold and Asc-Px by 90%. The results of the present study reveal (1) the Prevalence of oxidative stress inT. foenum-graecum during Se deficiency, (2) enhanced mitochondrial functional efficiency mediated by Se and mimosine independently, and (3) an antitoxidative role for mimosine during Se deficiency. The study demonstrates for the first time that mimosine, a naturally occuring toxic amino acid, could be a beneficial growth factor in concentrations between 0.1 and 0.2 mM.
19 citations
Cites background from "Selenium-mediated biochemical chang..."
...Experimental Se deficiency in animals has been widely studied (14-17), which indicates reversible and specific Se-dependent enzyme modulation in a variety of species....
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TL;DR: In this article, the requirement, uptake, and subcellular distribution of Na2 · 75SeO3 in the larvae of C. cephalonica was investigated, and a more fundamental role for selenoprotein in the mitochondrial energy metabolism emerges from these studies.
Abstract: Requirement, uptake, and subcellular distribution of Na2
75SeO3 in the larvae of the insectC. cephalonica was investigated. That Se is well tolerated byC. cephalonica upto an added level of 2 ppm in the diet is suggested by the observed increase in body weight, total protein, and succinate dehydrogenase levels. Significant increases in the State 3 respiration ensued with Se supplementation up to 2 ppm in the mitochondrial oxidation of D-glycerol 1-phosphate, succinate and NADH, along with concomitant unaltered State 4 respiration, leading to enhanced RCR values. Maximal uptake of75Se was registered in the larvae maintained on basal diet when subjected to short-term exposure to 0.5 ppm75Se level. When exposure level was further increased up to 20 ppm, the observed decrease in the uptake of75Se suggested that Se status of larvae itself controlled the tissue uptake. Subcellular distribution pattern revealed maximal incorporation of75Se (cpm/g tissue) in the supernatant fraction, whereas, maximal specific75Se activity (cpm/mg protein) was associated with the mitochondrial fraction. Autoradiography of the soluble fractions indicated the presence of single selenoprotein in the larval group with short term 2 ppm75Se exposure. Inherent Se controls both the extent and the nature of distribution of mitochondrial75Se incorporation. Uptake of45Ca by the insect mitochondria was enhanced by dietary Se up to 2 ppm but was unaffected by addition ofin vitro
75Se in the medium. A more fundamental role for Se in the mitochondrial energy metabolism emerges from these studies.
16 citations
TL;DR: The study reveals a differential response to Se among the β-galactosidase and β-glucosid enzyme of T. foenumgraecum with increase in the levels of β-GalactOSidase activity.
Abstract: Beta-glucosidase and beta-galactosidase activity profile tested in different seeds during 24 h germination revealed reasonably high levels of activity in Vigna radiata, Cicer arietinum, and Trigonella foenum-graecum. In all seeds tested, beta-galactosidase activity was, in general, higher than that of beta-glucosidase. T. foenum-graecum seedlings exhibited maximal total and specific activities for both the enzymes during 72 h germination. Se supplementation as Na2SeO3 up to 0.75 ppm was found to be beneficial to growth and revealed selective enhancement of beta-galactosidase activity by 40% at 0.5 ppm Se. The activities of both the enzymes drastically decreased at 1.0 ppm level of Se supplementation. On the contrary, addition of Na2SeO3 in vitro up to 1 ppm to the enzyme extracts did not influence these activities. Hydrolytic rates of beta-glucosidase in both control and Se-supplemented groups were enhanced by 20% with 0.05 M glycerol in the medium and 30% at 0.1 M glycerol. The rates were marginally higher in Se-supplemented seedlings than the controls, irrespective of added glycerol in the medium. In contrast, hydrolysis by beta-galactosidase showed a trend of decrease in Se-supplemented seedlings compared to the control, when glycerol was present in the medium. Addition of Se in vitro in the assay medium showed no difference in the hydrolytic rate by beta-galactosidase when compared to control, while the activity of beta-glucosidase declined by 50%. Se-grown seedlings showed an enhancement of transglucosidation rate by 40% in the presence of 0.1 M glycerol. The study reveals a differential response to Se among the beta-galactosidase and beta-glucosidase of T. foenum-graecum with increase in the levels of beta-galactosidase activity.
6 citations
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TL;DR: These experiments establish the existence of a selenoprotein, 75 Se-P, in rat liver and plasma which is chromatographically distinct from glutathione peroxidase and which incorporates 75 Se differently from glutATHione per oxidase.
Abstract: The selenoenzyme glutathione peroxidase cannot account for all the physiological effects of selenium in rat liver. Therefore, a study was carried out with the ultimate aim of identifying selenoproteins other than glutathione peroxidase. The incorporation of 75 Se, given as 75 SeO 3 2− , into centrifugally separated fractions of selenium-deficient and control rat livers was determined. In selenium-deficient liver much less 75 Se was incorporated into the 105,000 g supernatant fraction than in controls, so this fraction was studied further by gel filtration, ion-exchange, and hydroxylapatite chromatography. Selenoglutathione peroxidase and another selenoprotein, called 75 Se-P, were separated and identified. Both these selenoproteins were also found in plasma. Selenium deficiency had opposite effects on incorporation of 75 Se by these proteins. It decreased 75 Se incorporation by glutathione peroxidase at 3 and 72 h after 75 Se injection but increased 75 Se incorporation by 75 Se-P. This suggests that 75 Se-P competes for available selenium better than does glutathione peroxidase when the element is in short supply. Apparent molecular weights of 75 Se-P from liver and plasma determined by gel filtration were, respectively, 83,000 and 79,000, which indicate proteins smaller than glutathione peroxidase. Cycloheximide pretreatment of the rat blocked 75 Se incorporation into plasma 75 Se-P. These experiments establish the existence of a selenoprotein, 75 Se-P, in rat liver and plasma which is chromatographically distinct from glutathione peroxidase and which incorporates 75 Se differently from glutathione peroxidase. 75 Se-P may account for some of the physiological effects of selenium.
117 citations
TL;DR: It was concluded that a reactive site involving a sulfhydryl group is intimately involved in either the entrance of inorganic phosphate into the mitochondrion or in the formation of a phosphorylated intermediate essential for oxidative phosphorylation and ion transport.
Abstract: The influence of the sulfhydryl reagent 5,5′-dithio-bis-(2-nitrobenzoic acid) (DNTB) on metabolism of liver mitochondria was studied under different experimental conditions. 1. 1. DTNB prevented the stimulation of respiration produced by ADP and inorganic phosphate in the presence of glutamate or succinate but had little effect on 2,4-dinitrophenol-stimulated respiration. 2. 2. The formation of ATP from ADP and phosphate was depressed by DTNB. The inhibition could be reversed by dithiothreitol. 3. 3. The increase in mitochondrial oxygen uptake produced by calcium and phosphate was depressed by DTNB. 4. 4. The uptake of calcium by mitochondria in the presence of ATP and glumate was only partially inhibited by DTNB. In contrast, the stimulatory effect of inorganic phosphate on calcium transport was completely prevented. 5. 5. In the presence of glutamate and no added ATP the uptake of calcium was associated with an entrance of phosphate. DTNB almost abolished the uptake of phosphate and inhibited calcium uptake by about 60%. The decrease in calcium uptake produced by DTNB was equal, mole for mole, to the decrease in phosphate uptake. 6. 6. DTNB completely prevented the extrusion of calcium exhibited by calcium-loaded mitochondria incubated in the presence of inorganic phosphate and a low concentration of magnesium. 7. 7. N-Ethylmaleimide had effects similar to DTNB but in addition severely inhibited 2,4-dinitrophenol-stimulated respiration with glutamate as substrate. 8. 8. It was concluded that a reactive site involving a sulfhydryl group is intimately involved in either the entrance of inorganic phosphate into the mitochondrion or in the formation of a phosphorylated intermediate essential for oxidative phosphorylation and ion transport.
92 citations
TL;DR: It is suggested that the labeled moiety is a selenopolypeptide whose function is critical for normal assembly of the sperm tail.
Abstract: Selenium is necessary for normal sperm tail development in the rat. The biochemical locus of this requirement was investigated by intratesticular administration of (75Se)Se03−2. Sperm were labeled primarily in tail keratin, a disulfide-stabilized fraction obtained by extracting isolated tails with sodium dodecyl sulfate (SDS). By incubation in 1% SDS−0.2 mM dithiothreitol, followed by sonication and centrifugation, the 75Se was separated from a residue rich in S and Zn, composed of dense fibers and connecting pieces. The extracted 75Se-labeled material was non-dialyzable, sensitive to pronase, retained most of its bound isotope following carboxymethylation, and displayed only one radioactive component, of 17,000 daltons, during SDS-polyacrylamide gel electrophoresis. It is suggested that the labeled moiety is a selenopolypeptide whose function is critical for normal assembly of the sperm tail.
91 citations
TL;DR: The glutathione peroxidase enzyme was isolated as a neutrally charged protein and became negatively charged upon storage, a phenomenon that was independent of the aggregation.
Abstract: The subcellular distributions of glutathione peroxidase and 75Se in rat liver were determined. Approximately 75% of the enzyme and 58% of the 73Se were contained in the cytosolic fraction. Rat liver cytosol glutathione peroxidase was purified 1029-fold from homogenate to yield a sample with a specific activity of 278 μmol of NADPH oxidized/ min/mg of protein. The purified enzyme was subjected to disc-gel and sodium dodecyl sulfate-disc-gel electrophoresis, which confirmed the purity of the enzyme as well as the existence of multiple electrophoretic forms. Glutathione peroxidase existed as a large aggregate after homogenization, and means of dissociating the aggregate were investigated. The enzyme was isolated as a neutrally charged protein and became negatively charged upon storage, a phenomenon that was independent of the aggregation.
74 citations