Plasma selenium

This is illustrated for the non-pregnant subjects in this example in Figure 4 The slope for the first 3 days corresponds to a pool size of 230 ug Se An interesting coincidence is that the plasma selenium concentrations and the estimated plasma volumes (very similar in these subjects) correspond to about 230 ug of circulating plasma selenium This may, of course, be coincidence, but since plasma and urine can exchange things in the kidneys one might speculate that there is perhaps more to it than coincidence ... 

Whole blood selenium levels can vary between 10 and 3000 ng Se/ml. These levels reflect dietary Intake. With an Se intake of about 50 pg/day, plasma Se levels in humans are about 70 ng/ml, and red blood cell Se is about 90 ng/ml (Levander et a ., 1983). Maximal activity of GSH peroxidase, as determined by assays of the platelet enzyme, is supported where the plasma selenium level is about 100 ng/ml. 

Selenium has functions in many selenoproteins and also in relation to the immune response. There is an association between low plasma selenium concentrations and oral cancer (1). Selenium compounds inhibit tumorigenesis in a variety of animal models, and added selenium in human diets might reduce the risk of cancer (SEDA-21, 240). 

In 15 patients who had a serious adverse reaction to valproate (including behavioral changes and emesis in six, raised aspartate transaminase in three, raised aspartate transaminase and pancreatitis in one, thombocytopenia in two, and unexpected death in two), erythrocyte glutathione peroxidase activity and plasma selenium and zinc concentrations were significantly reduced, whereas erythrocyte glutathione reductase activity was significantly raised... 

Studies with infants have clearly shown that plasma Se levels respond to dietary Se levels. A very rough correlation may be made from the available data. A 2.5-fold increase in selenate intake provoked a 66% rise in plasma selenium levels (T5o ala et al, 1996). 

The concentrations of selenium in whole blood and in plasma and/or serum are related to dietary intake. About 50% to 60% of the total plasma selenium is present as the protein selenoprotein P, a highly basic protein having multiple histidine residues and about 10 atoms of selenium per molecule, Around 30% of plasma selenium is present as glutathione peroxidase (GSHPx-3) and the remainder is incorporated into albumin as selenomethionine. ... 

Early animal studies and human population surveys used whole blood as the main indicator of selenium status. Whole blood selenium can be determined after acid digestion using a fluorometric method. The more convenient carbon furnace atomic absorption spectroscopy (CFAAS) assay for plasma and/or serum selenium is now the most widely used procedure. The main components of plasma selenium are extracellular glutathione peroxidase (GSHPx 3) and selenoprotein P. 

Plasma selenoprotein P, plasma GSPHx-3, and total plasma selenium concentration are aU lowered by the APR to injury or infection. This effect should be considered when interpreting plasma selenium values in postoperative patients or those with infection or inflammatory disease. 

In summary, there are many possible markers for selenium status. In practice, measurement of plasma selenium or GSHPx provides a good estimate of status and in particular the adequacy of recent intake, provided they are interpreted in the knowledge of changes in the APR. For a better index of long-term intake, platelet, red cell, or neutropinl GSHPx, or hair or nail selenium can also be measured. 

The reference interval for selenium in whole blood, plasma or serum, hair, and nails should be established locally, since these indices are affected by dietary selenium intake. Plasma selenium adult values lie in the interval 63 to 160pg/L (0.8 to 2.0pmol/L). Values of less than 40 pg Se per L (0.5pmoI/L) indicate probable selenium depletion. 

Nichol C, Herdman J, Sattar N, O Dwyer PJ, St JO, Littlejohn D, Fed G. Changes in the concentrations of plasma selenium and selenoproteins after minor elective surgery further evidence for a negative acute phase response Clin Chem 1998 44 1764-6. 

Selenium toxicity may occur when patients receive doses exceeding 200 mcg/kg per day for prolonged periods. Selenium status may be assessed by measuring plasma selenium concentrations, which will reflect recent selenium intake. Decreased concentrations may indicate selenium deficiency, but reductions also have been observed in patients with malignancies, liver failure, and pregnancy. Assays that... 

Temple KA, Smith AM, Cockram DB. Selenate-supplemented nutritional formula increases plasma selenium in hemodialysis patients. J Ren Nutr 2000 10 16-23. 

There is a rapid decline in serum selenium levels 1 hour after intravenous administration of sodium selenite or sodium selenate to humans (Burk 1974 Nelp and Blumberg 1965). Burk (1974) found that 50% of the plasma selenium was protein-bound within the first 2 hours after administration 85% was bound within 4-6 hours after administration and 95% was bound after 24 hours. Circulating alpha-2 globulins have been reported to have the greatest affinity for selenium (Hirooka and Galambos 1966a). Burk (1974) found that lipoproteins, primarily the very low density lipoprotein (VLDL) and the low-density lipoprotein (LDL) fractions, were also involved in selenium binding. 

Cenac A, Simonoff M, Moretto P, et al. 1992. A low plasma selenium is a risk factor for peripartum cardiomyopathy. A comparative study in Sahelian Africa. Int J Cardiol 36(l) 57-59. 

Clark LC, Graham GF, Crounse RG, et al. 1984. Plasma selenium and skin neoplasms A case-control study. Nutr C ancer 6 12-21. 

Lewis SA, Hardison NW, Veillon C. 1986. Comparison of isotope dilution mass spectrometry and graphite furnace atomic absorption spectrometry with Zeeman background correction for determination of plasma selenium. Anal Chem 58 1272-1273. 

Perona G, Cellerino R, Guidi GC, et al. 1977. Erythrocytic glutathione peroxidase Its relationship to plasma selenium in man. Scand J Haematol 19 116-120. 

Sesana G, Baj A, Toffoletto F, et al. 1992. Plasma selenium levels of the general population of an area in northern Italy. Sci Total Environ 120(l-2) 97-102. 

Pregnant long-tailed macaques (Macaca fascicularis) given L-selenomethionine for 30 days at doses of 25.0,150.0, or 300.0 (xg Se/kg body weight daily showed dose-dependent increases in erythrocyte and plasma selenium, glutathione peroxidase activities, hair and fecal selenium, and urinary selenium excretion. Adverse effects, including body weight loss, were associated with daily doses of 150.0 and 300.0 xg Se/kg BW and with concentrations of erythrocyte selenium >2.3mg/L,... 

Selenium status is also adversely affected by chronic ethanol intake. Recently, Dutta et aL (1983) showed a significant depression in plasma selenium levels in hospitalized alcoholics. Urinary excretion was also low in these subjects, who were otherwise well nourished. The authors pointed out that alcoholic beverages contain very low levels of selenium. Several investigators have demonstrated that in the selenium-deficient animal, hepatic preneoplastic foci development is enhanced (O Connor et aL, 1983 O Connor and Campbell, 1984). Ethanol could thus indirectly enhance tumor development by depleting selenium stores. 

Susceptibility factors Renal disease Plasma copper, selenium, and zinc concentrations and antioxidant metalloenzymes, glutathione peroxidase (GPX) and superoxide dismutase (SOD), were studied in 17 patients on maintenance hemodialysis, 14 uremic patients, and 14 healthy subjects [46 ]. Plasma selenium concentrations and erythrocyte GPX were significantly lower in those on hemodialysis, and the two were correlated. There was also a correlation between reduced plasma zinc and erythrocyte SOD activity. 

However, evidence for selenosis due to high selenium exposure is rather limited. In regions of the Brazilian Amazon, despite the fact that blood and plasma selenium concentrations surpass levels considered toxic (1000 rg/L), no symptoms of toxicity were found associated with biomarkers. The median levels of blood- and plasma selenium were 228.4 rg/L (range 103.3-1500.2 rg/L) and 134.8 gg/L (range 53.6-913.2 gg/L), respectively. Thus, further investigations assessing selenium chemical form, route of exposure and co-exposure need to be evaluated [222 j. 

In a study in Liverpool, UK, healthy adult subjects with initial plasma selenium concentrations below... 

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