SEARCH · PubMed Health

Results for “Selenomethionine”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 19 recordsLinked to original sources

PubMed1975

Metabolic studies in rats of (75-Se)selenomethionine and of 75-Se incorporated in vivo into rabbit kidney.

1. [75-Se]selenomethionine was administered to four rabbits and after 4 d their kidneys were removed and homogenized. The long-term fate in rats of an oral dose of this kidney homogenate (RK-75-Se) was compared with that of an oral dose of ]75-Se]selenomethionine mixed with unlabelled rabbit kidney homogenate. 2. Urinary adn faecal radioactivities were measured during the 1st week and whole-body radioactivity was determined for 10 weeks. Rats were killed at weekly intervals for 4 weeks for analysis of tissue distribution of 75-Se. 3. Intestinal absorption of RK-75-Se was 87%; that of [75-Se]selenomethionine was 91%. Urinary excretion of absorbed RK-75-Se was 13-3% and that of [75-Se]selenomethionine was 7-6%, in the 1st week. 4. Whole-body retention of 75-Se was greater for [75-Se]selenomethionine than for RK-75-Se but after the 1st week decreased at a similar rate in both groups. Tissue distribution of retained 75-Se was also similar in both groups. 5. The initial utilization of 75-Se in rabbit kidney is different from that of [75-Se]selenomethionine. However, after the 1st week 75-Se from these sources appears to be metabolized similarly, suggesting that Se from both is ultimately incorporated into the same metabolic pool.

Animals↗

PubMed1979

Vitamin B6 dependence of selenomethionine and selenite utilization for glutathione peroxidase in the rat.

The biological availability of selenium from sodium selenite and selenomethionine for glutathione peroxidase activity was studied. Rats were fed ad libitum for 2 weeks a basal diet deficient in both selenium and vitamin B6, and then for the subsequent 2 weeks the same diet supplemented with vitamin B6 (2.5 micrograms as pyridoxine-HCl/g diet) or selenium (2 microgram/g diet) or both. In the presence of vitamin B6, selenite and selenomethionine increased equally the glutathione peroxidase activity in both the liver and erythrocytes above that of selenium-unsupplemented controls. In the absence of vitamin B6, selenomethionine was less effective in the liver and ineffective in the erythrocytes while selenite was equally effective in both tissues and was as effective as in the presence of vitamin B6. These results indicate that selenite selenium is readily available for glutathione peroxidase induction as compared with selenomethionine, and establish that vitamin B6 is involved in the metabolism of selenomethionine to supply selenium for glutathione peroxidase.

Animals↗

PubMed1976

Biological potency of selenium from sodium selenite, selenomethionine, and selenocystine in the chick.

Experiments were conducted to determine the relative effectiveness of selenium (Se) from sodium selenite, selenomethionine and selenocystine for promoting weight gain and preventing exudative diathesis. The chicks used were hatched from eggs low in Se. They were fed a basal diet made up mostly of corn (low in Se) and torula yeast or the basal diet supplemented with various levels of Se from sodium selenite, selenomethionine, or selenocystine. At 10 mug. of added Se per kg of diet, sodium selenite and selenocystine were about equal in promoting weight gain and preventing exudative diathesis. Selenomethionine was less effective. Tissues from chicks fed the various Se sources providing 60 mug. Se per kg of diet for four weeks were analyzed for Se. The content of tissues from chicks fed sodium selenite or selenocystine was similar. Chicks fed selenomethionine had a higher concentration of Se in the pancreas and breast muscle than chicks fed the other two Se sources, but a lower concentration in the kidney, liver, and heart. The level of Se in the kidney, liver, or heart which a Se source produces seems to be more important for preventing exudative diathesis than that which is found in the pancreas or muscle.

Animals↗

PubMed1979

Catalytic action of L-methionine gamma-lyase on selenomethionine and selenols.

We examined the catalytic action of L-methionine gamma-lyase (EC 4.4.1.11) on selenomethionine (2-amino-4-(methylseleno)butyric acid), methaneselenol, l-hexaneselenol, and benzeneselenol. The enzyme catalyzes alpha, gamma-elimination of selenomethionine to yield alpha-letobutyrate, ammonia, and methaneselenol, and also its gamma-replacement reaction with various thiols to produce S-substituted homocysteines. Selenomethionine is an even better substrate than methionine in alpha, gamma-elimination but is less effective in gamma-replacement. In addition, L-methionine gamma-lyase catalyzes gamma-replacement reaction of methionine and its derivatives with selenols to form the corresponding Se-substituted selenohomocysteines, although selenols are less efficient substituent donors than thiols. This is the first proven mechanism for the incorporation of selenium atom into amino acids.

Benzene Derivatives↗

PubMed1978

Selective uptake of 75Se-selenomethionine by thymoma with pre red cell aplasia.

Red cell aplasia and an enlarging anterior mediastinal mass developed in a patient being followed for thyroid carcinoma. Differential diagnosis included thymoma and metastatic thyroid carcinoma. Preoperative scanning demonstrated significant uptake of 75Se-selenomethionine whereas 67Ga-galiium citrate failed to visualize the mass. Subsequent thoracotomy revealed a lymphocytic thymoma which was resected, resulting in reversal of the red cell aplasia. The use of 75Se-selenomethionine scanning maybe a useful adjunct in the preoperative evaluation of suspected thymomas.

Adenocarcinoma↗

PubMed1979

Dose dependent uptake of 125I-toluidine blue of 75Se-selenomethionine in the parathyroids of rabbits.

Different dosages of 125I-toluidine blue and 75Se-selenomethionine were injected intravenously into rabbits, and the concentration of radioactivity was measured in the parathyroids and surrounding tissues. The response of i.v. injected glucagon was also determined. It was found that 0.16 mg 125I-toluidine blue gave a concentration ratio of parathyroid/thyroid and parathyroid/muscle which was significantly higher than both lower and higher doses at 1 minute after i.v. injection of the labelled dye. Glucagon had little or no effect on the uptake of 125I-toluidine blue and 75Se-selenomethionine.

Animals↗

PubMed1979

The distribution of 75Se-adenosyl selenomethionine in the rat with observations on its potential as a prostate scanning agent.

The preparation of 75Se-adenosyl selenomethionine is described. Following injection into male rats 63% of the administered label was excreted in 24 h, predominantly in the urine. The remaining activity appeared to have joined the S-adenosyl methionine pool residing mainly in the liver and kidney. The maximum incorporation into the ventral prostate was 2 to 4 h after injection at 0.7% injected dose/g wet weight. These results indicate that 75Se-adenosyl selenomethionine is not a suitable radiopharmaceutical for diagnostic scanning of the prostate.

Animals↗

PubMed1978

Studies on the microcytotoxicity test. III. Comparison of [75Se]selenomethionine with [3H]proline, Na2, 51CrO4 and [125I]iododeoxyuridine for pre-labelling target cells in long-term cytotoxicity tests.

Four intracellular radioisotope labels, [3H]proline, Na2 51CrO4, [75Se]selenomethionine and [125I]iododeoxyuridine, were evaluated for use in a pre-labelling long-term microcytotoxicity assay for cell-mediated immunity. Adherent rat tumour cells established in tissue culture were used as targets and the basic variables studied were labelling efficiency, toxicity and spontaneous release rates. [125I]Iododeoxyuridine was found unsuitable on account of its high toxicity and correspondingly high spontaneous release rate, and Na2 51CrO4 for its toxicity and low labelling efficiency. Of the two other radiolabels, [75Se]selenomethionine had the advantage over [3H]proline of higher labelling efficiency (especially in Ham's F10 medium), lower toxicity, and being a gamma-emitter. Furthermore, released 75Se was shown to be non-reutilisable and its retention by target cells provided an accurate measure of cell survival in an alloimmune system. Methods of calculating the results of pre-labelling cytotoxicity tests based on the total radioactivity in target cells at the beginning of the assay were found to be invalid.

Animals↗

PubMed1978

Use of [75Se]selenomethionine in immunoglobulin biosynthetic studies.

The gamma-emitting amino acid analog, [75Se]selenomethionine, has been used as a biosynthetic label for immunoglobulins secreted by plasmacytomas in tissue culture. The secreted products are structurally intact with respect to their antibody combining sites and their class and allotype antigenic specificities. A component of [75Se]selenomethionine preparations was found to bind to fetal calf serum proteins, in a manner releasable by mercaptoethanol, but not by sodium dodecyl sulfate (SDS) and urea. Methods for circumventing the problems caused by this binding are described.

Animals↗

PubMed1976

The metabolism of [75Se]selenomethionine in four women.

1. The long-term fate of an oral dose [75Se]selenomethionine was studied in four women. 2. Urinary and faecal excretion, respiratory losses and whole-body retention of 75Se were measured, and also 75Se turnover in whole body, plasma and erythrocyte during a period of 33-34 weeks. 3. Intestinal absorption of [75Se]selenomethionine by the four subjects was 95.5-97.3% of the administered dose. 4. Urinary excretion accounted for 6-9% of absorbed 75Se in the first 2 weeks. No radioactivity was detected in expired air.

Adult↗

PubMed1977

Effects of selenite and selenomethionine on glutathione peroxidase in the rat.

The activity of glutathione (GSH) peroxidase (EC 1.11.1.9) decreased in tissues of rats fed a diet deficient in selenium. A single dose of 300 mug selenium by stomach tube increased GSH peroxidase activity within 48 hours. The effects of selenite and selenomethionine on GSH peroxidase activity were roughly similar. This study provides evidence that selenium from both selenite and selenomethionine is readily available for synthesis of the selenoenzyme GSH peroxidase in rat tissues.

Animals↗

PubMed1979

Oscillations in tissue uptake of 75Se-L-selenomethionine in rats and mice adapted to controlled feeding schedules.

The amino acid 75Se-L-selenomethionine was used to study variations in amino acid uptake by various tissues of rats and mice adapted to a schedule of controlled feeding and lighting conditions. Food only became available for an 8-hour period at the beginning of the 12-hour dark period of the 24-hour cycle. Systematic oscillations were observed in the uptake of selenomethionine by the liver, pancreas, blood, kidneys, skeletal muscle, bone and brain of both rats and mice but only very small changes were noted in the spleen, lung and heart. The level of the uptake into the liver and pancreas and possibly the kidney appear to be related to the dietary state of the animals.

Amino Acids↗

PubMed1979

Growth-hormone and somatostatin effects on [75Se]selenomethionine uptake by the pancreas.

The imaging of the pancreas with [75Se]selenomethionine has a low rate of reliability. This study was carried out in order to elucidate some factors that may be important in affecting the degree of uptake of the tracer by the pancreas. Studies were carried out in animals to observe the effects of growth-hormone (GH), somotostatin (SRIF), L-DOPA, and apomorphine administration on the distribution of [75Se]selenomethionine. Intravenously administered GH significantly depressed pancreatic uptake of Se-75 in mice and dogs and depressed the pancreas-to-liver concentration ratio (P/L). The effect of i.p. GH in mice was to decrease the P/L ratio, but the decrease in pancreatic uptake was not statistically significant. There was also a greater effect of GH in dogs than in mice, with pancreatic uptake decreasing from 5.60 +/- 2.17% to 1.24 +/- 0.96% and the P/L from 4.78 +/- 1.85 to 0.97 +/- 0.73. L-DOPA and apomorphine produced effects similar to GH in mice. SRIF in small doses had little effect, but in larger doses it enhanced pancreatic uptake, although not affecting P/L. The results indicate that hypothalamic factors may be important in affecting the function of the exocrine pancreas. Both L-DOPA and apomorphine are known to stimulate GH production through hypothalamic-pituitary pathways. In addition to suppressing GH release, SRIF may have direct effects on the exocrine pancreas.

Animals↗

PubMed1978

[Hypophyseal-adrenocortical system reaction to the prolonged action of low doses of selenomethionine-75Se that form during internal contamination].

A method of radiometry in vivo was applied to study the regularities attending distribution of the absorbed dose and its formation in the course of one year after the administration of 0.033 muCu/g of selenomethionine-75Se to rats, as well as the functional condition of the adaptive hypophysis-adrenal glands system by the determination of plasma corticosterone. A high tropicity of this preparation to the endocrine system organs was demonstrated. Intensification of the functional activity of the adaptive system was indicated by an increase of the blood plasma corticosterone concentration following the administration of a, radioactive preparation and its statistically significant increase (in comparison with control) 3, 6, and 10 months from the beginning of the experiment. The action of acute stress (histamine and formalin) 10 months after the administration of selenomethionine-75Se caused no sharp elevation of the plasma corticosterone concentration characteristic of control rats, this indicating an extreme strain of the hypophysis-adrenal gland system and its incapacity to respond to additional loads. It is supposed that analysis of functional condition of the adaptive system could serve as the key in the assessment of the biological effect of low radiation doses.

Acute Disease↗

PubMed1975

75Se-selenomethionine-labeled lipoproteins in hyperlipidemic and normolipidemic humans.

Investigating the feasability and application appropriate to determination of lipoprotein turnover, 75Se-selenomethionine (Se-M) incorporation in lipoproteins was studied in eight hospitalized patients. Three were hyperlipidemic diabetic subjects (HL), and five were normolipidemic but otherwise abnormal subjects (NL). Maximum activity was observed in the VLDL fraction within 2-3 hr, and was followed by a biexponential decay. Incorporation into the LDL-I (density, 1.006-1.019 mug/ml) occurred at a rate which correlated with the rapid decay rate of the VLDL Se-M activity. The decay of the Se-M was single exponential in the LDL-I and LDL-II (density, 1.019-1.063 mug/ml), suggesting undirectional transfer of the label. The HDL fraction showed a rapid initial Se-M uptake which was followed by a slow rise, resulting in a complex time-activity curve. The Se-M activity was significantly higher in the VLDL fraction and slightly lower in the LDL and HDL fractions in the HL as compared to the NL subjects. The VLDL-apoprotein concentration increased by a significantly greater amount in the HL (374 mug/ml) than in the NL subjects (67 mug/ml). There was a significant increase in VLDL-apoprotein turnover in the presence of a fractional turnover rate that was not significantly lower in the three hyperlipidemic subjects compared to the NL controls. In vivo 75Se-selenomethionine labeling allows the estimation of the synthesis and removal rate of apoproteins.

Adult↗

PubMed1976

Further clinical evaluation of the selenomethionine uptake test.

A review of the selenomethionine uptake ratio as a measure of placental function is presented. Attempts at the early identification of the poorly growing fetus were unsuccessful, and the previously published close correlation of results with clinical findings in later pregnancy has not been confirmed. The theoretical basis of the test has been re-examined. Although modification much reduced the incidence of technically unsatisfactory readings, other difficulties prevented the test from being clinically useful. To some extent the aim of the test has been superseded by concurrent developments and advances in care of the premature baby.

Evaluation Studies as Topic↗

PubMed1976

Incorporation of 75Se-selenomethionine into human apoproteins. I. Characterization of specificity in very-low-density and low-density lipoproteins.

Characterization of specificity of incorporation of 75Se-selenomethionine into human apoproteins following in-vivo injection of the radioactive amino acid precursor is reported. Apoprotein fractionation was attained by serial ultracentrifugation, anhydrous partial delipidization, decyl sulfate solubilization with Sephadex G-150 gel filtration into polypeptide fractions, Sf-I, and Sf-II, for VLDL, and LDL subfractions. Similarity of the Sf-I fractions isolated from VLDL, LDL1, and LDL2 was defined by gel exclusion volume, disk-gel electrophoresis, immunodiffusion, and amino acid composition. Enrichment of the Sf-I fractions with 75Se-SM in VLDL and LDL subfractions was observed, suggesting a possible use for this isotopic method for the investigation of apoprotein metabolism.

Amino Acids↗

PubMed1976

Incorporation of 75Se-selenomethionine into human apoproteins. III. Kinetic behavior of isotopically labeled plasma apoprotein in man.

The metabolism of lipoprotein-apoprotein was examined in four subjects with normal lipid metabolism and in one subject with type II hyperlipemia by means of isotopic tracer methodology. Studies were performed after intravenous injection of a radioactive amino acid precursor for apoprotein synthesis (75Se-selenomethionine), in both the basal state and following the acute injection of intravenous heparin. Computer technics were used to evaluate a series of multicompartmental models, and a general model is proposed that yields optimum fitting of experimental data for serum free amino acid precursor, very-low-density lipoprotein-apoprotein (VLD-apoprotein), and low-density lipoprotein-apoprotein (LDL-apoprotein) in man. The analysis demonstrates that approximately half of the transport of 75Se-apoVLDL from the plasma VLDL pool is converted to 75Se-apoLDL. The acute injection of heparin in two normal subjects results in a two-and-a-half-fold increase in this rate of conversion of 75Se-apoVLDL to 75Se-apoLDL. 75Se-apoLDL is metabolized by rapid transport into a recycling extravascular pool and by irreversible catabolism. The fractional rate of recycling is large relative to the fractional rate of catabolism of apoLDL (3.7:1.0), suggesting extravascular recycling as a potential site of regulation of the plasma concentration of apoLDL. In a patient with type II hyperlipemia, the extravascular recycling pathway is reduced and is not corrected with D-thyroxine therapy. However, this therapy did reduce conversion of apoVLDL to apoLDL in this type II patient. The kinetic data support the validity of the compartmental model in simulating both normal and pathologic apoprotein metabolism and that perturbation of physiology seen with heparin injection and D-thyroxine therapy. These data support a quantitative role of apoVLDL as a precursor of apoLDL and identify an important recycling pathway of apoLDL metabolism in addition to that of catabolism.

Adult↗