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PubMed1989

Plasma selenium-dependent glutathione peroxidase. Cell of origin and secretion.

Human plasma glutathione peroxidase (GSHPx) has been shown to be a glycosylated selenoprotein distinct enzymatically, structurally, and antigenically from known cellular glutathione peroxidases. The extracellular location of the enzyme and the fact that it is glycosylated suggested that it is a secreted protein. Utilizing mutually non-cross-reactive antibodies to human cellular and plasma GSHPx, we conducted a search to determine the tissue of origin for plasma GSHPx. The cells screened were endothelial cells because they are the main source of extracellular superoxide dismutase, HL-60 cells (myeloid cell line) because they are the main source of extracellular H2O2, and Hep G2 cells (hepatic cell line) because they are the source of many plasma proteins. Human umbilical vein endothelial cells were metabolically labeled with either [35S]methionine or [75Se]selenious acid, and HL-60 cells and Hep G2 cells were metabolically labeled with [75Se]selenious acid. Proteins were immunopurified from the labeled cells and their media with either anti-red blood cell (RBC) GSHPx IgG or with anti-plasma GSHPx IgG. Utilizing anti-RBC GSHPx IgG, only the cellular form of the enzyme was precipitated from all the cells tested but not from their media. When anti-plasma GSHPx IgG was applied to the cells and their media, a selenoprotein was precipitated only from the media of Hep G2 cells. When Hep G2 cells were incubated in the presence of the carboxylic ionophore monensin, an intracellular selenoprotein could be detected using anti-plasma GSHPx IgG. The precipitation of the cellular form from all three cell types was partially inhibited by preincubation of the anti-RBC GSHPx IgG with purified RBC GSHPx while the precipitation of the selenoprotein from the medium of Hep G2 cells by anti-plasma GSHPx IgG was prevented by preincubation of the antibody with purified plasma GSHPx. We suggest that plasma GSHPx is synthesized by and secreted from hepatic cells. This is, to the best of our knowledge, the only known selenoprotein with a defined function that has been shown to be synthesized for secretion by mammalian cells.

Cell Line↗
PubMed1999

Determination of selenium compounds by HPLC with ICP-MS or FAAS as selenium-specific detector.

A speciation method was developed for selenious acid, selenic acid, trimethylselenonium ion (TMSe) and selenomethionine (SeMet). Separation of the four selenium species was achieved by HPLC on an ESA Anion III anion-exchange column using aqueous mobile phase of 5.5 mmol/L ammonium citrate at pH 5.5 with a flow rate of 1.5 mL/min. Under the optimal conditions, the four selenium species were separated within 8 minutes. On-line selenium-specific detection was carried out with an inductively coupled plasma mass spectrometer (ICP-MS) or a flame atomic absorption spectrometer (FAAS). The detection limits of HPLC-FAAS were approximately rho(Se) = 1 mg/L for each compound (100 microL injection). To increase the nebulization efficiency of the ICP-MS, the Meinhard concentric nebulizer was replaced by an ultrasonic nebulizer (USN). The ICP-MS signal intensity was increased by a factor of 7 for selenious acid and 24 to 31 for TMSe, SeMet and selenic acid with the USN compared to that with the Meinhard nebulizer. The detection limits of the HPLC-USN-ICP-MS were rho(Se) = 0.08 microgram/L for TMSe, rho(Se) = 0.34 microgram/L for selenious acid, rho(Se) = 0.18 microgram/L for SeMet and rho(Se) = 0.07 microgram/L for selenic acid.

Chromatography, High Pressure Liquid↗
PubMed2000

A fatal case of gun blue ingestion in a toddler.

Acute selenium poisoning occurs infrequently. The form of selenium encountered plays a great role in toxicity. Several fatalities have been reported and all but I involved ingestion of selenious acid or selenium dioxide. A healthy 22-mo-old male ingested up to 15 ml of Gun Blue solution (selenious acid). Initially he was pink, alert, and combative in the ambulance but his condition rapidly deteriorated. There was no measurable blood pressure, his oxygen saturation was 84% by pulse oximetry, and his mental status deteriorated to require hand ventilation. The child was cyanotic, unresponsive, and without palpable pulses upon presentation. Cardiopulmonary resuscitation was initiated unsuccessfully and was terminated after 35 minutes.

Blood Pressure↗
PubMedDate not supplied

Post firing visualisation of fingerprint on spent cartridge cases.

A considerable range of techniques is available to visualise latent fingerprints on smooth surfaces. Published methods and those developed or modified in the authors' laboratory have been evaluated for spent cartridge cases. The most suitable were found to be vacuum cyanoacrylate (with fluorescent staining) and selenious acid treatments. Both were used to investigate the post firing recovery of finger-marks on spent cartridge cases from the ammunition and weapon systems encountered in terrorist casework in Northern Ireland. Only certain revolvers and the SLR rifle yielded identifiable ridge detail. These results are borne out by casework experience.

Cyanoacrylates↗
PubMed1986

Proximal muscle weakness and selenium deficiency associated with long term parenteral nutrition.

A 33-yr-old white female with short bowel syndrome secondary to trauma was maintained on home parenteral nutrition for 4 yr when her plasma, red cell, white cell, and platelet glutathione peroxidase (GSHPx) activities were found to be extremely low, as were her plasma and red cell selenium levels. During her first year on parenteral nutrition she noted the onset of an inability to rise from a squatting position, rapid tiring when stair climbing, and weakness when attempting to lift large or moderately heavy objects. Treatment with 400 micrograms/d of selenious acid intravenously was associated with a disappearance of her symptoms and an increase in proximal muscle strength within 6 wk. The plasma and red cell selenium levels, and the plasma and white cell GSHPx activities rose to normal levels within 6 wk. Red cell GSHPx activity returned to normal by 3 mo.

Adult↗
PubMed1985

Fatal acute selenium toxicity.

Selenium is used widely in industry and as a dietary supplement. Reports of acute selenium toxicity are infrequent, however, and the relationship of toxicity to selenium concentrations in blood and tissues has not been established. We describe a patient who died eight days after ingesting selenious acid in the form of gun blueing. The patient's clinical course demonstrated many of the features of inorganic selenium toxicity described in animals; hypotension as a result of both vasodilation and decreased cardiac output, adult respiratory distress syndrome, severe myopathy which contributed to respiratory failure, and a garlicky odor to the breath. Four days after ingestion the serum selenium concentration was twenty times normal and urinary excretion seventy times normal. Postmortem tissue selenium concentrations were up to 40 times normal.

Female↗
PubMed1988

Interactions of gold with cytosolic selenium-containing proteins in rat kidney and liver.

Rats injected with aurothioglucose (ATG) for 5 days were subsequently injected with [75Se]selenious acid and killed after 3 days. Kidney and liver cytosols were chromatographed on Sephadex G-150. 75Se in kidney was associated with high molecular weight (HMW), 85,000 Mr, 26,000 Mr, and 10,000 Mr proteins and with a nonprotein fraction. The elution profile of liver cytosol was similar to that of kidney, but without a 26,000 Mr protein. ATG injection increased the association of 75Se with all fractions of kidney cytosol except the 85,000 Mr fractions, which contained Se-glutathione peroxidase (SeGSHPx) activity; 75Se in liver was increased only in HMW fractions. Unfractionated kidney cytosolic SeGSHPx activity was decreased 14% by ATG injection, but liver enzyme activity was not changed. However, Sephadex G-150 chromatography showed that total and specific activities, respectively, were decreased 28 and 23% in kidney and 25 and 16% in liver. Au coeluted with HMW and 10,000 Mr 73Se-containing kidney proteins; the latter contained 50% of the Au eluted from the column. DEAE Sephacel chromatography of the 10,000 Mr kidney protein showed that both Au and 75Se were tightly associated with metallothionein-like proteins. This study demonstrates the interaction of Au with rat liver and kidney 75Se-containing proteins.

Animals↗
PubMed1995

Molecular cloning and functional expression of a cDNA for rat phospholipid hydroperoxide glutathione peroxidase: 3'-untranslated region of the gene is necessary for functional expression.

A full-length cDNA clone for phospholipid hydroperoxide glutathione peroxidase (PHGPx) was isolated from a rat brain. The cDNA was 0.761 kb in length and encoded 170 amino acids, which included a TGA-encoded selenocysteine at residue 46. The protein has a calculated molecular mass of 19,473 Da. We succeeded in the transient functional expression of a full-length cDNA for PHGPx, which includes the 3'-UTR, in COS-7 cells at the first attempt. Deletion of the 3'-UTR prevented the expression of the PHGPx activity and the incorporation of [75Se]selenious acid into the monomeric 19.7 kDa PHGPx protein. Thus, the 3'-UTR of the cDNA for PHGPx was required for the functional expression of PHGPx. Northern blot analysis demonstrated that the mRNA for PHGPx was widely expressed in normal rat tissues, especially in the testis. The mRNA levels of PHGPx in the cultured cells such as hepatomas, neuronal cells, nephroblastoma, and mammary myo-epithelial cells were higher than those of the tissues. The ratio of PHGPx to cytosolic glutathione peroxidase (cGPx) was significantly high in the testis and relatively high in the cultured cells. The mRNA levels of PHGPx in tissues were lower than those of cGPx.

Amino Acid Sequence↗
PubMed1979

Mineral metabolism of the healing arterial wall.

The mineral metabolism of healing arterial walls was studied by measuring the accumulation of several radioisotopes at the site of vascular repair in rats. Each rat was subjected to a 1-cm full-thickness aortotomy and then immediately injected by tail vein with c 5 muCi of one of the following radioisotopes: chromic chloride Cr 51 or sodium chromate Cr 51; ferrous chloride Fe 59 or ferric chloride Fe 59; manganous chloride Mn 54; selenious acid Se 75; strontium chloride Sr 85; or zinc chloride Zn 65. At intervals of 1, 2, 4, 6, and 10 days after operation and injection, groups of four rats for each radioisotope were killed, aortas dissected, and the specific radioactivity of healing vascular tissue compared with that of adjacent normal artery. There were sharp and statistically significant differences in the preferential accumulation of the radioisotopes in healing compared with normal aorta. Zinc appeared to be the element most involved in vascular repair, followed by selenium and chromium.

Animals↗
PubMed1996

Stromal cells of the human prostate: initial isolation and characterization.

The present study was conducted to isolate and to characterize stromal cells from the human prostate and to study the effects of androgen and different growth factors in this model system. Benign prostatic hyperplasia (BPH) tissue samples were obtained from transurethral resection of the prostate (TURP). Tissue specimens were mechanically and enzymatically dissociated by treatment with DNAse and collagenase. Epithelial cells were separated from stromal cells by discontinuous Percoll gradient centrifugation. The stromal cells obtained were cultured in phenol red-free RPMI-1640 supplemented with 10% fetal bovine serum. Immunocytochemical analysis revealed that the stromal cell cultures were composed of both smooth muscle cells and fibroblasts. The short and broad, smooth muscle cells wee identified by using an antibody directed against alpha-smooth muscle actin. The thin and elongated fibroblasts stained positively for prolyl 4-hydroxylase. Smooth muscle cells were the predominant cell type in the present investigation. Typical cultures contained up to 99% of cells staining positively for alpha-smooth muscle actin. The prostate smooth muscle cultures were treated with dihydrotestosterone (DHT), bovine pituitary extract (BPE), basic fibroblast growth factor (bFGF) and transforming growth factor-beta (TGF-beta). When cells were cultured in serum free RPMI-1640 supplemented with ITS+ (insulin, transferrin, and selenious acid) no significant (P > 0.05) mitogenic effect in medium supplemented with ITS+. In the presence of 10% charcoal-stripped fetal bovine serum (cFBS) DHT, at a concentration of 0.1 nM, was able to cause a slight but significant (P < 0.05) mitogenic effect on BPH smooth muscle cells growth. Basic FGF was able to stimulate BPH smooth muscle cells in a concentration-dependent fashion. The combination of DHT and 0.1 ng/ml bFGF was able to increase the proliferation of prostate smooth muscle cells above either agents alone. Addition of BPE to serum free RPMI-1640 caused a significant (P < 0.05) stimulation of cell proliferation in a concentration-dependent fashion. Addition to TGF-beta to serum or BPE containing RPMI-1640 caused a significant (P < 0.05) inhibition to cell proliferation in a concentration-dependent fashion. TGF-beta was cytostatic to the benign prostatic smooth muscle cells only in the presence of media containing growth stimulating factors found in charcoal-stripped serum or in bovine pituitary extract. These results demonstrated that stromal fraction isolated from BPH specimens was composed of both fibroblasts and smooth muscle cells. These cells could be cultured and were able to respond to various growth stimulatory and inhibitory agents.

Cell Division↗
PubMed1981

Selenium-sulfur analogs III: synthesis and biodistribution of two 75Se-labeled 4-substituted-1,2,3-selenadiazoles.

The 75Se-labeled 4-substituted-1,2,3-selenadiazole analogs of two drugs that inhibit the adrenocorticosteroid 11 beta- and 17 alpha-hydroxylase enzymes were prepared by the [75Se]selenious acid oxidation of the appropriate methyl ketone semicarbazones. The concentration of the radiolabeled compounds in the adrenal glands of rats over a 0.25--24-hr period was determined and compared with that in the blood, liver, and kidneys. The concentration in the adrenal glands and the target to nontarget ratios were much lower than those reported for other adrenocorticosteroid inhibitors. Therefore, these 1,2,3-selenadiazole agents do not have potential as adrenocorticosteroid imaging agents.

Adrenal Cortex↗
PubMed2003

Antigenotoxic properties of selenium compounds on potassium dichromate and hydrogen peroxide.

Selenium is an environmental metal that occurs ubiquitously and is produced throughout the world for various industrial activities. Selenium has been reported to have anticarcinogenic and preventive effects in clinical and epidemiological studies. Selenium supplements can inhibit chemically-induced tumours. From the viewpoint of genotoxicity, selenium has not been adequately studied and an IARC review concluded that there were not sufficient data to consider it a carcinogen for man. In contrast, hexavalent chromium is classified as a known respiratory carcinogen producing DNA damage through free oxygen radicals. In the present study, a collaborative study has been carried out to evaluate the genotoxicity of selenium compounds and their possible interactions with potassium dichromate and hydrogen peroxide. Thus, in laboratory 1 (U.K.), the genotoxic effects of three selenium compounds were examined. Sodium selenate, sodium selenite, and selenous acid were investigated in the Ames test using strain TA102 and in the Comet assay using human lymphocytes, and also investigated for their interaction with potassium dichromate. In the Ames test, it was shown that potassium dichromate produced a highly mutagenic response, whilst the three selenium compounds did not. In combination, sodium selenate reduced the genotoxicity of potassium dichromate, but sodium selenite and selenous acid had no effect. In the Comet assay, potassium dichromate induced DNA damage, but so did the selenium compounds. In combination with potassium dichromate, however, only sodium selenate reduced its effect, whereas sodium selenite and selenous acid exacerbated DNA damage. In laboratory 2 (Spain), in the TK6 lymphoblastoid cell line, the Comet assay showed that sodium selenite was non-genotoxic, while potassium dichromate and hydrogen peroxide induced DNA damage. It was also shown that sodium selenite did not decrease the genotoxicity of potassium dichromate or hydrogen peroxide when administered as a pre-treatment or at the same time, or when potassium dichromate and sodium selenite treatments were for different time periods. Thus, only sodium selenate has shown antigenotoxic properties against potassium dichromate in the Ames test and in human lymphocytes in the Comet assay.

Comet Assay↗
PubMed1987

Acute selenium poisoning of a 2-year-old child.

After ingestion of an unknown amount of a gun blueing compound containing selenious acid (11 ml from the bottle fluid were missing, equivalent to 2.9 g Se) a 2-year-old girl suffered from continuous hyper-salivation, vomiting, diarrhoea, restlessness and muscle spasm. Blood pressure and pulse rate were increased. Symptomatic treatment was performed by parenteral fluid administration. The plasma Se concentration was increased to 20 times normal 5 h after ingestion. Erythrocyte Se exceeded plasma Se, 24 h after intoxication. Urinary Se excretion decreased parallel to the plasma Se concentration. Ten weeks later, the Se content of hair had risen to 10 times normal. The plasma glutathione peroxidase activity showed only a slight increase during the first 36 h, erythrocyte glutathione peroxidase, catalase and superoxide dismutase activities were not significantly altered. The child fully recovered.

Child, Preschool↗
PubMedDate not supplied

The toxicity and bioaccumulation of selenate, selenite and seleno-L-methionine in the cyanobacterium Anabaena flos-aquae.

A laboratory investigation was conducted to study the toxicity and bioaccumulation of seleno-L-methionine, selenate and selenite in the cyanobacterium Anabaena flos-aquae. The first sub-lethal effects of seleno-L-methionine, selenite and selenate occurred at 0.1, 3.0, and 3.0 mg/L, respectively with a decrease in chlorophyll a concentration (P less than 0.0001). Selenium bioconcentration factors (BCF) were in the order of seleno-L-methionine, selenite, and selenate. Significant decreases in intracellular selenium concentration were observed at both the no effect (NOEL) and low effect levels (LOEL) at each oxidation state tested in the given experiment (p less than 0.0001). Mechanisms for the assimilation, toxicity and regulation of selenium are presented.

Cyanobacteria↗
PubMed1992

Comparison of molecular properties of rat plasma and erythrocyte selenium-dependent glutathione peroxidase.

The molecular structure of plasma and erythrocyte selenium-dependent glutathione peroxidase (GSH-Px) was studied in rats drinking water containing [75Se]selenious acid, 1.3 mg Se/L. Substantial differences were found using three-step fractionation, including gel filtration of crude plasma and erythrocyte lysate, gel filtration of 75Se-GSH-Px treated by mercaptoethanol, and SDS-electrophoresis. Native plasma 75Se-GSH-Px, which exhibited a molecular weight (M(r)) of approx. 700,000, could be destroyed by mercaptoethanol action, resulting in disintegration of enzyme into several different 75Se-protein fragments and release of part of low-mol-wt 75Se. Native erythrocyte 75Se-GSH-Px M(r) value was found to be 113,000; two 75Se-protein fragments arose after mercaptoethanol treatment without 75Se release from the enzyme. The 75Se-subunits of 22,500 and 21,900 were isolated from plasma and erythrocyte 75Se-GSH-Px, respectively. Another minor 75Se-GSH-Px was identified in erythrocyte lysate (M(r) 214,000, subunit 22,100), which was considered to be a dimer of the above-mentioned erythrocyte enzyme. It can be assumed, based on these data, that native plasma GSH-Px, in contrast to erythrocyte enzyme, represents a high-molecular wt complex composed of several tetramers linked with S-S bonds. A certain part of selenium present in this complex is probably not selenocysteine and may be released with the mercaptoethanol treatment.

Animals↗
PubMedDate not supplied

Metabolic differences and similarities of selenium in blood and brain of the rat following the administration of different selenium compounds.

A common intermediate, i.e., selenite, was found in the serum of the rat; the maximum levels occurred 3 h after administration independent of chemical forms. This indicates that both the reduction of selenate to selenite, and oxidation of seleno-dl-methionine to selenite existed in the metabolic pathways of the rat. We found that water-soluble selenium compounds led to a similar maximum content in blood and serum, but seleno-dl-methionine had a higher affinity for the brain and, by gel filtration chromatography, for the higher mol-wt (25-100 K Da) fractions of serum protein, when compared with inorganic forms.

Animals↗
PubMedDate not supplied

Comparison of whole blood selenium values and erythrocyte glutathione peroxidase activities of normal individuals on supplementation with selenate, selenite, L-selenomethionine, and high selenium yeast.

The selenium levels and the glutathione peroxidase activity GSH-PX of whole blood and of erythrocytes, respectively, were determined in 139 normal Danes and related to sex and smoking habits. No differences were found in relation to sex apart from a higher GSH-PX activity of females when assayed with tertiary butyl hydroperoxide. Smokers showed significantly lower selenium values than non-smokers (p less than 0.05), but the two groups had identical GSH-PX activities. Individuals from the above-mentioned group were divided into four groups, receiving daily oral doses of 200 micrograms of selenium in the form of selenite, selenate, L-selenomethionine, and selenium as contained in yeast. Whole blood selenium values and the erythrocyte glutathione peroxidase activities were determined during three months of supplementation followed by a withdrawal period of four months. Both the inorganic selenium compounds and the organic derivatives gave rise to steady state levels of GSH-PX after one month of supplementation. However, the selenium levels in the groups receiving organic selenium showed a steady rise during the whole period, whereas those supplemented with inorganic selenium leveled off after a period of one to three months. The data for smokers and nonsmokers revealed identical results when organic selenium was supplemented. However, selenite gave rise to significantly higher selenium levels and GSH-PX activities in smokers than in non-smokers. Less significant (p less than 0.08) elevations of both parameters were also observed among the smokers in the selenate group. By taking both the selenium level and the GSH-PX activity into consideration, organic selenium (i.e., L-(+) selenomethionine) was judged to be more bioavailable than selenite and selenate.

Adult↗