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PubMed1983

Modification of the effects of aflatoxin B1 and warfarin in young pigs given selenium.

Selenium may be related to the hepatic metabolism of the coumarin compounds aflatoxin B1 and warfarin. Selenium evidently increased the pharmacologic activity of warfarin, probably due to a displacement of warfarin from albumin by selenium, the close relationship among selenium, vitamin E, and sulphur-containing groups (eg, glutathione), or the antioxidant effect of selenium. A diet containing selenium in a concentration of 2.5 mg/kg of feed was protective against the toxic effects of both coumarins in pigs given 4 daily oral doses of 0.2 mg/kg of body weight. Selenium, as glutathione peroxidase, at least in part, protects the hepatic cells against the toxic effects of aflatoxin B1 and warfarin. The protection was demonstrated by alteration of clinical responses and hematologic (prothrombin times), electrophoretic, and clinical chemistry values. It also was demonstrated that selenium at 2.5 mg/kg of feed does not produce toxic effects; however, dietary selenium at a concentration of 5 mg/kg (and in the presence of both toxic agents) was toxic for young pigs within the 3-week experimental period. Warfarin was more active as an anticoagulant than aflatoxin B1.

Aflatoxin B1↗
PubMed1978

The influence of selenium on the level of mercury and metallothionein in rat kidneys in prolonged exposure to different mercury compounds.

Mercuric chloride, phenylmercuric chloride, ethylmercuric chloride /0,23 mg Hg/kg/ and methylmercurycyan guanidine /0,46 mg Hg/kg/ were orally administered to rats every second day for 14 weeks. The same doses of the above mentioned mercury compounds were administered alternately with sodium selenite /0,18 mg Se/kg/ to parallel groups of rats at the same time. The level of total and inorganic mercury and of metallothionein was determined. All mercury compounds increased the level of metallothionein in rat kidneys. In rats which received only selenium the level of metallothionein was twice lower in the kidneys in relation to the physiological level of this protein. Selenium eliminated the stimulation of biosynthesis of metallothionein by mercury.

Animals↗
PubMed1984

Investigation of two fluorinated reagents for the analysis of selenium by gas chromatography.

As potential reagents for the determination of traces of selenium by gas chromatography, the compounds 4-fluoro-o-phenylenediamine and 4-trifluoromethyl-o-phenylenediamine have been examined and compared with seven o-diamines previously reported for analytical purposes. Retention times of the fluoro-piaselenols are shorter than all other compounds but, with the electron-capture detector, their responses differ widely. However, the detection limit of the trifluoromethylpiaselenol compares favourably with the commonly used derivative, 5-nitropiaselenol. The analytical requirements of 4-trifluoro-o-phenylenediamine as a reagent, and the results of its application to the determination of selenium in various biological matrices, are presented.

Animals↗
PubMed1989

Acute toxicity and urinary excretion of diphenyldiselenide.

The acute toxicity of diphenyldiselenide (DPDS) in the male Swiss mouse was found to be enhanced by pretreatment with phenobarbital of SKF-525A. DPDS decreased hepatic glutathione content by 50% at 1 h after administration. Following administration of 14C-DPDS, labelled metabolites were found in urine but not in bile or feces. Analysis of the urinary metabolites of 14C-DPDS showed that selenium-containing metabolites elute from a DEAE-Sephadex column in two fractions: the first has not been chemically characterized, while the second peak contained the glucuronide conjugates of C6H4(OH)SeH and C6H5SeH. Virtually all of the administered selenium is excreted within 5 days, while only about 36% of the 14C is excreted in the same time period. This discrepancy indicates metabolic scission of the carbon-selenium bond.

Animals↗
PubMed1989

Porcine focal symmetrical poliomyelomalacia: test for an interaction between dietary selenium and niacin.

Experiments were conducted to test the hypothesis that dietary supplementation with nicotinamide would retard or eliminate the signs of selenium induced porcine focal symmetrical poliomyelomalacia (PFSP). Mixed-sex feeder pigs, approximately five weeks old, were divided into four groups and daily received, by oral capsule, the following treatments: no supplementation (control); 2.86 mg sodium selenite per kg body wt (selenium only); 44 mg nicotinamide per kg body wt (niacin only); or both the niacin and selenium (niacin + selenium). Over the ten day treatment body weights and behavior scores were recorded, as well as collection of fluid (blood, serum, urine) samples. Upon death, tissue samples (kidney, liver, brain, spinal cord and muscle) were obtained. All of these samples were analyzed for total selenium and bioactive niacin compounds. After gross pathological analysis, 11 samples from specific brain and spinal cord regions were taken for fixation and processing for histological analysis by light microscopy. The selenium only group showed behavior signs related to PFSP after two days of treatment with the average time of death at 6.5 days. Tissue levels of selenium were elevated and histological analyses established the expected lesions of PFSP. No disorders were noted in the control and niacin only groups. The niacin + selenium groups had slightly retarded changes in behavior scores (first differences from controls on day 4) but their mean day of death (7.5 days of treatment) did not differ from that of the selenium only groups. Histological analyses of these tissues revealed similar lesions to the selenium only group, but they may have been of lesser magnitude. The data were consistent with, but only partially supportive of, the above hypothesis.

Animals↗
PubMed1993

Toxicity, bioavailability and metal speciation.

1. Environmental toxicology emphasizes the difference from traditional toxicology in which pure compounds of interest are added to purified diets, or injected into the test animals. When the objective is to study the fate and effects of trace elements in the environment, knowledge of the speciation of the elements and their physico-chemical forms is important. 2. Cadmium salts such as the sulfides, carbonates or oxides, are practically insoluble in water. However, these can be converted to water-soluble salts in nature under the influence of oxygen and acids. Chronic exposure to Cd is associated with renal toxicity in humans once a critical body burden is reached. 3. The solubility of As(III) oxide in water is fairly low, but high in either acid or alkali. In water, arsenic is usually in the form of the arsenate or arsenite. As(III) is systemically more poisonous than the As(V), and As(V) is reduced to the As(III) form before exerting any toxic effects. Organic arsenicals also exert their toxic effects in vivo in animals by first metabolizing to the trivalent arsenoxide form. Some methyl arsenic compounds, such as di- and trimethylarsines, occur naturally as a consequence of biological activity. The toxic effect of arsenite can be potentiated by dithiols, while As has a protective effect against the toxicity of a variety of forms of Se in several species. 4. Selenium occurs in several oxidation states and many selenium analogues of organic sulfur compounds exist in nature. Selenium in selenate form occurs in alkaline soils, where it is soluble and easily available to plants. Selenite binds tightly to iron and aluminum oxides and thus is quite insoluble in soils. Hydrogen selenide is a very toxic gas at room temperature. The methylated forms of Se are much less toxic for the organism than selenite. However, the methylated Se derivatives have strong synergistic toxicity with other minerals such as arsenic. 5. Aquatic organisms absorb and retain Hg in the tissues, as methylmercury, although most of the environmental Hg to which they are exposed is inorganic. The methylmercury in fish arises from the bacterial methylation of inorganic Hg. Methylmercury in the human diet is almost completely absorbed into the bloodstream. The nervous system is the principal target tissue affected by methylmercury in adult human beings, while kidney is the critical organ following the ingestion of Hg(II) salts.

Animals↗
PubMed1996

[Selenium, glutathione peroxidase, peroxides and platelet functions].

In the last five years, there has been a renewal of interest in the protective role of selenium in vascular disorders, inspired by experimental evidence that this trace element could modulate leukotriene and prostaglandin synthesis in both endothelial cells and platelets. In people living in low-selenium areas, a relationship has been established between a decrease in plasma selenium and an increase in the risk of coronary disease, atherosclerosis, platelet hyperaggregability and synthesis of proaggregant and proinflammatory compounds like thromboxane A2 and leukotrienes. Selenium, as an essential part of glutathione peroxidase, takes part in the reduction of hydrogen peroxides and lipid peroxides. The concentration of these peroxides, in turn, regulates the activities of cyclooxygenase and lipooxygenase pathways, ultimately influencing the production of eicosanoids and modulating the balance between a proaggregatory and antiaggregatory state. Recent evidence shows that selenium, via its action on glutathione peroxidase activity, may be primarily responsible for the regulation of the endogenous hydroperoxide level. In human platelets, the activity of glutathione peroxidase is particularly high and is very sensitive to the requirement of selenium. This sensitivity could explain why platelets of selenium-deficient subjects show increased aggregation, thromboxane B2 production and synthesis of the lipoxygenase-derived compounds. In these deficient subjects, selenium administration increases platelet glutathione peroxidase activity and inhibits platelet hyperaggregation and leukotriene synthesis. These results support the hypothesis that selenium supplementation has a positive effect on platelet aggregation in selenium-deficient subjects. In France, more than 10% of the population is selenium-deficient and long-term supplementation with low doses of selenium could have a beneficial effect on the prevention of both thrombosis and coronary heart disease in these subjects.

Animals↗
PubMed2000

Effects of arsenic-, platinum-, and gold-containing drugs on the disposition of exogenous selenium in rats.

Having found that the electrophilic model compound sulfobromophthalein markedly altered the fate of exogenous selenium in the body by reacting in vivo with nucleophilic selenium metabolites, the effects of metal-containing drugs with expected selenium reactivity were tested on biliary, urinary, and pulmonary excretion. Tissue distribution of selenium in selenite-injected rats was also examined. Coadministration with [(75)Se]selenite (10 micromol/kg, iv) of the trypanosomicid arsenicals (100 micromol/kg, iv) trimelarsan (TMA) or melarsoprol (MAP), the antitumor cisplatin (25 micromol/kg, iv), or the antirheumatic gold sodium thiomalate (25 or 50 micromol/kg, iv) significantly altered the disposition of (75)Se, whereas carboplatin (100 micromol/kg, iv) did not produce such an effect. The most dramatic alterations included the approximately 20-fold increase in the biliary excretion rate of selenium in response to TMA and MAP, the almost complete cessation of the exhalation of selenium as dimethyl selenide after administration of the arsenic- and gold-containing drugs, and the manifold accumulation of selenium in the blood plasma following gold injection. Direct chemical reaction of the drugs with nucleophilic selenite metabolites in the body may underlie these alterations. The tight coordination in time and extent observed between the biliary excretion of arsenic and selenium in rats receiving either of the arsenicals and selenite supports this hypothesis. However, attempts to detect selenium-containing biliary metabolites of TMA and MAP have failed, possibly owing to their instability. In summary, the arsenic-, platinum- and gold-containing drugs significantly influence the fate of exogenous selenium, whereby they may adversely affect the availability of this essential element for synthesis of selenoenzymes. Furthermore, the capability of TMA and MAP to enhance the biliary and total excretion of selenium renders these drugs significant candidates for antidotes in selenium intoxication.

Animals↗
PubMed2004

Au2(SeO3)2(SeO4): synthesis and characterization of a new noncentrosymmetric selenite-selenate.

The reaction of elemental gold and selenic acid in Teflon-lined steel autoclaves leads to orange-yellow single crystals of Au2(SeO3)2(SeO4) (orthorhombic, Z = 4, Cmc2(1) (No. 36), a = 1689.1(3) pm, b = 630.13(8) pm, c = 832.7(1) pm, V = 886.2(2) angstroms3, Rall = 0.0452). In the crystal structure, Au3+ is surrounded by four oxygen atoms of just as many monodentate SeO3(2-) ions in a square planar manner. The linkage of the polyhedra leads to double chains in the [001] direction which are connected to puckered layers by SeO4(2-) groups. The noncentrosymmetric space group could be proved by the observation of an SHG effect upon irridation at 1064 nm that shows an efficiency of about 43% compared to a KDP reference. Upon heating, Au2(SeO3)2(SeO4) decomposes at about 370 degrees C in one step yielding elemental gold. The presence of selenite and selenate groups in the compounds is also obvious from the IR and Raman spectra which show the characteristic bands of both species. Furthermore, solid-state NMR spectra reveal the different surroundings of the selenium atoms in the compound.

Journal Article↗
PubMed1984

Inhibition of aflatoxin B1 carcinogenesis in rainbow trout by flavone and indole compounds.

Several compounds such as flavonoids, selenium, antioxidants and retinoids reportedly reduce the induction of cancer in experimental animals, and some have been suggested to function by affecting the mixed-function oxidase (MFO) system. The following compounds: 50 and 500 p.p.m. beta-naphthoflavone (BNF), 1000 p.p.m. flavone, 1000 p.p.m. of a tangeretin - nobilitin mixture, 1000 p.p.m. beta- ionone , 1000 p.p.m. indole-3-carbinol ( I3C ) and 2000 p.p.m. quercetin were examined for protection against aflatoxin B1 (AFB1) hepatocarcinogenesis, induction of the MFO system and metabolism of AFB1 in rainbow trout. These compounds were fed to fingerling rainbow trout for 8 weeks. At that time the activity of several MFO enzymes and cytochrome P450 content were measured and the trout were exposed for 2 weeks to 20 p.p.b. AFB1 in the same diets. After feeding the test diets without AFB1 for another 6 weeks and basal diet for another 52 weeks, the tumor incidence was determined. The effect of BNF and I3C on in vivo binding of AFB1 to DNA was also measured in separate groups of trout. BNF induced the trout MFO system in a dose-dependent manner, tangeretin - nobilitin was less effective and I3C did not induce. BNF showed significant alterations in the metabolism of AFB1 to aflatoxicol and aflatoxin M1 using cell fractions from pretreated fish. None of the other compounds, including I3C showed such an effect. Despite the apparent lack of in vitro effect of I3C , both BNF and I3C reduced AFB1 - DNA binding in vivo. I3C and BNF provided marked protection against AFB1-induced hepatocarcinogenesis, while the other compounds were less effective. The 58 weeks tumor incidences were 4% for 1000 p.p.m. I3C , 6% for 500 p.p.m. BNF and 18% for 50 p.p.m. BNF, compared to 38% for the AFB1-positive control. These data demonstrate that gross induction of the MFO system was not necessarily required for alterations in DNA adduct formation in vivo or protection against AFB1 carcinogenesis. Both BNF and I3C provided marked protection but only BNF induced the MFO system.

Aflatoxin B1↗
PubMed1976

Biotransformation of methylmercury in vitro.

Inorganic mercury formation from methylmercury by the mouse liver and kidney was studied in vitro. With chopped liver or kidney, inorganic mercury was formed from added methylmercury, but when the tissue was homogenized, the activity was diminished. Equimolar addition of selenium had no effect on the reaction.

Animals↗