Liver Selenium Concentrations Research Articles

Concentrations of Mercury and Selenium in Tissues of Double-Crested Cormorants (Phalacrocorax auritus) from Southern Florida

-Tissues from 99 Double-crested Cormorants (Phalacrocorax auritus) collected between 1994 and 1997 from southern Florida, were analyzed for concentrations of mercury and selenium. These concentrations were correlated with each other, including concentrations of mercury and selenium in liver. Mercury and selenium in liver increased from a mean of 15 and 8 mg kg'l wet weight (ww) in the fall, winter and spring to a mean of 41 and 13 mg kg'l ww in the summer, respectively. Similarly, concentrations of mercury in brain increased from a mean of 1.3 mg kg-1 ww in the fall, winter and spring to a mean of 2.2 mg kg'1 ww in the summer. Concentrations of selenium in liver increased with age. Sex, physical condition, year, and geographic location of recovery had no significant effect on mercury and selenium concentrations. Between 12 and 15% of the cormorants studied had hepatic selenium and mercury concentrations of over 20 and 50 mg kg'1 ww, respectively (considered lethal in some avian species). Liver selenium concentrations of over 3 mg kg' ww and brain mercury concentrations above 2 mg kg-' ww (related to reproductive failure in adult loons and mallards) were observed in 57% and 32% of the cormorants studied, respectively. These results could mean that Double-crested Cormorants in southern Florida might be at risk of mercury and selenium poisoning. Received 17 November 1997, accepted 3 March 1998.

Influence of Gender on Selenoprotein W, Glutathione Peroxidase and Selenium in Tissues of Rats

After feeding a commercial rodent chow for 8 weeks, tissues from male and female rats were collected and examined for selenium content, glutathione peroxidase (GPX) activities and selenoprotein W (Se-W) levels. There were no differences (P > 0.05) between plasma selenium content, plasma GPX activity, whole blood selenium content, or whole blood GPX activity between male and female rats. There was also no gender effect on selenium concentration in muscle, brain, spleen, and skin, but selenium concentration in liver was higher (P < 0.05) in female than in male rats. Western blots indicated that the tissue distribution of Se-W was similar in male and female rats. Se-W protein level was high in testes of male rats but very low in ovaries of female rats. Muscle and skin from female rats had significantly higher (P < 0.05) Se-W levels than from male rats. Consistent with Se-W content, the Se-W mRNA levels from female skins were significantly higher (P < 0.05) than from male rats. The expression of Se-W was different in various tissues and gender influenced this regulation in some tissues.

Effects of mild chronic heat exposure on the concentrations of thiobarbituric acid reactive substances, glutathione, and selenium, and glutathione peroxidase activity in the mouse liver.

To determine whether mild and chronic heat stress leads to oxidative stress and to differentiate such effects of different exposure periods, we kept male ICR-mice at an ambient temperature of either 35 degrees C or 25 degrees C for 6 hours, 3 days, or 7 days and measured the concentrations of thiobarbituric acid reactive substances (TBARS), glutathione (GSH), selenium (Se), and glutathione peroxidase (GSH-Px) activities in the liver. Since the food consumption of the heat-exposed group was only half that of the control, we prepared pair-fed groups, which were kept at 25 degrees C and whose food consumption were limited to those of the heat-exposed group for the 3-day and the 7-day exposure. TBARS concentrations of the liver was significantly higher in the heat group than the control after the 3-day exposure, while there was no significant difference among the groups after the 7-day exposure. There was no significant difference in GSH concentrations between the heat-exposed group and the control after the 7-day exposure, when the GSH concentration of the pair-fed group was significantly lower than that of the control. Hepatic cytosolic Se GSH-Px activity in the heat group was significantly less than that in the control group after the 6-hour exposure and it tended to be lower in the heat group than that of the control group after the 7-day exposure, while there was no difference in the total GSH-Px activity among the three groups. Our results showed that mild and chronic heat exposure may cause oxidative damage to organisms and that GSH-related anti-oxidative systems would play an important role to defensive reaction.

Zinc, cadmium and selinium in Greenland fish

Concentrations of zinc, cadmium, mercury and selenium in muscle, liver, kidney, spleen and bone in marine fish from Greenland are presented. Tissue differences are apparent for all elements. Except for mercury, higher concentrations are found in liver and kidney than in muscle. In general, the mercury concentration is positively correlated with fish length while selenium concentration shows a negative correlation. No such correlations are evident for cadmium and zinc. Significant differences in heavy metals levels are often found between geographic locations. Although there is tendency for higher concentrations of cadmium, mercury and selenium in fish from North West Greenland compared to fish from other areas of Greenland, the geographical variation is not consistent. The results indicate that high natural year to year variations in element levels (up to 3 times) occur in fish. Mercury and cadmium concentrations show relatively strong inter-organ correlations, whereas this is not the case for selenium and zinc. Zinc and cadmium show a high degree of association in all tissues.

Study on biological activity of selenium-enriched mussel extract

In this study on the biological activity of selenium-enriched mussel extract, rats were randomly separated into three weight groups fed a basal selenium-deficient diet, diet supplemented by selenium from sodium selenite, and selenium enriched mussel extract, respectively. Body weights of the rats were determined and metabolic experiment was conducted after 4 weeks. The rats were killed after 8 weeks. Glutathione peroxidase activity and selenium content in liver and blood were determined. The results showed that selenium in mussel extract could be better absorbed by the rats and effectively promote their growth. There were no significant differences in glutathione peroxidase activity between the rats fed mussel extract or sodium selenite. Compared with sodium selenite group, the selenium content in blood and liver was significantly higher in the rats fed mussel extract.

Effect of doses of protected polyunsaturated fatty acids on indicators of selenium status of sheep

In monogastric animals, dietary polyunsaturated fatty acids ( pufa) have been shown to increase glutathione peroxidase ( gsh-px) activity in plasma and erythrocytes and to decrease plasma selenium concentration. Ruminants feeding on grass can have a high intake of pufa. In this experiment, sheep were dosed orally with protected pufa ( Pr-PUFA) for five weeks at 5 g kg liveweight −1 three times per week for the first week and at 8 g kg −1 for the following four weeks. The Pr-PUFA did not affect GSHPx activity in erythrocytes or plasma or liver selenium concentration, but did reduce the selenium concentration in muscles by between 20 and 30 per cent. In addition, liver iron concentration was reduced by about 42 per cent. The results suggest that dietary PUFA may affect the distribution of selenium rather than its absorption.

Heavy metals in laughing gulls: Gender, age and tissue differences

AbstractWe examined concentrations of lead, cadmium, mercury, manganese, selenium, and chromium in feathers, liver, kidney, heart, and muscle of known‐aged laughing gulls (Larus atricilla) that hatched in Barnegat Bay, New Jersey and were collected at John F. Kennedy International Airport, New York 1 to 7 years later. Concentrations differed significantly among tissues, and “tissue” entered all the regression models explaining the greatest variation in metal levels. Age of bird contributed significantly to the models for lead, cadmium, selenium, and chromium. Although there were significant gender differences in all body measurements except wing length, there were few differences in metal levels. Males had significantly higher lead levels in feathers, and females had significantly higher selenium levels in heart and muscle tissue. For lead, 3‐year olds had the highest levels in the heart, liver, and kidney, and levels were lower thereafter. Mercury levels in feathers and heart decreased significantly with age. Cadmium levels increased significantly with age for feathers, heart, liver, and muscle, although there was a slight decrease in the 7‐year olds. Selenium levels decreased significantly with age for all tissues. Chromium levels increased with age for liver and heart.

Biogeochemical interactions affecting hepatic trace element levels in aquatic birds

AbstractKnowledge of elemental interactions is important to the toxicological assessment of wildlife in the geochemical environment. This study determines the concentrations of Al, As, B, Ba, Be, Cd, Cr, Cu, Fe, Pb, Li, Mg, Mn, Hg, Mo, Ni, Se, Ag, V, and Zn in aquatic bird liver, fish liver, whole bivalves, insects, and waters in several aquatic ecosystems in northern California. There is evidence of strong in vivo and environmental interactions, including the observation of manganese as a possible cofactor or indicator in selenium bioaccumulation. The nearest neighbor selenium correlation in aquatic bird liver tissue that results from this work is Cd–Mn–Se–Hg–As. The correlation of liver selenium to manganese in vivo and the result that the majority of the variance in liver selenium concentration is contained in the manganese term of the regression model relating Se to Cd, Mn, and Hg is new knowledge in the study of aquatic birds. A linear relationship between liver selenium and environmental manganese (water and sediment) is found in the data, suggesting a water chemistry compartmentalization or activation of toxicants. Alternatively, the hepatic concentrations of selenium, manganese, and iron suggest induction of enzymes in response to oxidative stress.

Toxicity of seleno-L-methionine, seleno-DL-methionine, high selenium wheat, and selenized yeast to mallard ducklings

The toxicity of four chemical forms of selenium (seleno-L-methionine, seleno-DL-methionine, selenized yeast, and high selenium wheat) was compared in day-old mallard ducklings (Anas platyrhynchos). In the first experiment, in which the basal diet was 75% wheat, survival after 2 weeks was lower for ducklings fed 30 micrograms/g selenium as seleno-L-methionine (36%) than for ducklings fed 30 micrograms/g selenium as seleno-DL-methionine (100%) or 30 micrograms/g selenium from high selenium yeast (88%). The concentration of selenium at 2 weeks in the livers of survivors was similar for ducklings fed 15 micrograms/g selenium as seleno-DL-methionine (12 micrograms/g, wet weight), seleno-L-methionine (11 micrograms/g), and high selenium wheat (11 micrograms/g), but was lower when the selenium came from selenized yeast (6.2 micrograms/g). When fed 30 micrograms/g selenium from the various sources, the selenium concentrations in liver were 20 micrograms/g for seleno-DL-methionine, 19 micrograms/g for seleno-L-methionine, and 9.9 micrograms/g for selenized yeast. In a second experiment, in which the basal diet was a commercial duck feed, survival after 2 weeks was 100% in ducklings fed 30 micrograms/g selenium as seleno-DL-methionine, seleno-L-methionine, or selenized yeast. Selenium concentrations in liver were similar for ducklings fed the 30-micrograms/g selenium diets as the DL or L forms of selenomethionine (27 and 25 micrograms/g), but lower for ducklings fed selenized yeast (13 micrograms/g).(ABSTRACT TRUNCATED AT 250 WORDS)

Comparison of maternal blood and fetal liver selenium concentrations in cattle in California

SUMMARY Selenium concentration was measured in paired maternal blood samples and fetal liver specimens collected at a San Joaquin County, Calif, slaughterhouse (beef = 19, dairy = 54) and from bovine aborted fetuses submitted to the California Veterinary Diagnostic Laboratory System (CVDLS; beef = 20, dairy = 20). Of the slaughterhouse samples and specimens, dairy maternal blood selenium concentration was significantly (P &lt; 0.001) higher (mean ± sd; 0.22 ± 0.056 µg/ml) than that for beef breeds (0.137 ± 0.082 µg/ml). The CVDLS mean maternal blood selenium concentration for the dairy-breed samples (0.192 ± 0.028 µg/ml) was similar to that for the slaughterhouse dairy-breed samples, but was greater than that for the slaughterhouse beef-breed samples. Slaughterhouse mean fetal liver selenium content also was higher (P &lt; 0.001) for the dairy breeds (0.777 ± 0.408 µg/g), compared with the beef breeds (0.443 ± 0.038 µg/g). Mean fetal liver selenium content for slaughterhouse specimens was higher (P &lt; 0.002) than that for the CVDLS specimens (beef, 0.244 ± 0.149 µg/g; dairy, 0.390 ± 0.165 µg/g). At the CVDLS, dairy fetal liver content was greater (P &lt; 0.001) than that for beef breeds. Mean ratio of fetal liver selenium content to maternal blood selenium concentration was 3.53 ± 1.89 for dairy breeds at the slaughterhouse (liver-to-blood correlation [r] = 0.38), and was 2.11 ± 1.00 for dairy breeds at the CVDLS (r = 0.31) and 3.43 ± 1.50 for beef breeds (r = 0.58). Both slaughterhouse breed ratios were significantly (P &lt; 0.002) greater than the CVDLS dairy-breed ratio. On the basis of these results, breed and source location should be taken into account when interpreting selenium values. Fetal liver selenium content should only be used as a screening test and combined with whole blood selenium concentration from clinically normal herdmates to evaluate herd selenium status.

Comparison of Maternal Blood and Fetal Liver Selenium Concentrations in California Cattle

Selenium (Se) concentrations were measured inpaired maternal blood and fetal liver samples from aCalifornia slaughterhouse (SH) (beef=19, dairy=54) andfrom bovine abortions submitted to the California VeterinaryDiagnostic Laboratory System (CVDLS)(beef=20, dairy=20).

Age dependency of selenium and cadmium content in human liver, kidney, and thyroid.

Selenium and cadmium concentrations were investigated in 60 autopsy tissue samples obtained from fetal life up to adulthood (defined in this study as 25-87 y of age) in Styria, a moderately industrialized region in Austria that has a low selenium supply. During the first 2 y after birth, median liver selenium concentrations were slightly lower (i.e., 1.5 nmol/g wet weight) than concentrations found in fetal life (i.e., 2.9 nmol/g) and adulthood (2.1 nmol/g). Whereas in the fetal period median selenium content in the kidney cortex (2.1 nmol/g) and the thyroid gland (1.6 nmol/g) was lower than that found in the liver, the reverse was true for adults (i.e., kidney, 5.5 nmol/g; thyroid, 4.3 nmol/g). Tissue cadmium concentrations approached 0 during gestation. Accumulation in the kidney and liver commenced immediately after birth. In the thyroid gland of adults, significantly higher concentrations of cadmium were found. Median concentrations in adults showed no statistical significant age dependency (i.e., liver, 7.6 nmol/g; kidney, 59.8 nmol/g; thyroid, 11.2 nmol/g). In summary, the data revealed very low tissue selenium concentrations and low cadmium burdens for the Styrian population that was not exposed occupationally.

Contaminants and Sea Ducks in Alaska and the Circumpolar Region

We review nesting sea duck population declines in Alaska during recent decades and explore the possibility that contaminants may be implicated. Aerial surveys of the surf scoter (Melanitta perspicillata), white-winged scoter (M. fusca), black scoter (M. nigra), oldsqaw (Clangula hyemalis), spectacled eider (Somateria fischeri), and Steller's eider (Polysticta stellei) show long-term breeding population declines, especially the latter three species. The spectacled eider was recently classified threatened under the Endangered Species Act. In addition, three other diving ducks, which commonly winter in coastal areas, have declined from unknown causes. Large die-offs of all three species of scoters during molt, a period of high energy demand, were documented in August 1990, 1991, and 1992 at coastal reefs in southeastern Alaska. There was no evidence of infectious diseases in those scoters. The die-offs may or may not be associated with the long-term declines. Many scoters had elevated renal concentrations of cadmium (high of 375 micrograms/g dry weight [dw]). Effects of cadmium in sea ducks are not well understood. Selenium concentrations in livers of nesting white-winged scoters were high; however, the eggs they laid contained less selenium than expected based on relationships for freshwater bird species. Histological evaluation found a high prevalence of hepatocellular vacuolation (49%), a degenerative change frequently associated with sublethal toxic insult. Cadmium and selenium mean liver concentrations were generally higher in those birds with more severe vacuolation; however, relationships were not statistically significant. We do not know if sea duck population declines are related to metals or other contaminants.

Contaminants and sea ducks in Alaska and the circumpolar region.

We review nesting sea duck population declines in Alaska during recent decades and explore the possibility that contaminants may be implicated. Aerial surveys of the surf scoter (Melanitta perspicillata), white-winged scoter (M. fusca), black scoter (M. nigra), oldsqaw (Clangula hyemalis), spectacled eider (Somateria fischeri), and Steller's eider (Polysticta stellei) show long-term breeding population declines, especially the latter three species. The spectacled eider was recently classified threatened under the Endangered Species Act. In addition, three other diving ducks, which commonly winter in coastal areas, have declined from unknown causes. Large die-offs of all three species of scoters during molt, a period of high energy demand, were documented in August 1990, 1991, and 1992 at coastal reefs in southeastern Alaska. There was no evidence of infectious diseases in those scoters. The die-offs may or may not be associated with the long-term declines. Many scoters had elevated renal concentrations of cadmium (high of 375 micrograms/g dry weight [dw]). Effects of cadmium in sea ducks are not well understood. Selenium concentrations in livers of nesting white-winged scoters were high; however, the eggs they laid contained less selenium than expected based on relationships for freshwater bird species. Histological evaluation found a high prevalence of hepatocellular vacuolation (49%), a degenerative change frequently associated with sublethal toxic insult. Cadmium and selenium mean liver concentrations were generally higher in those birds with more severe vacuolation; however, relationships were not statistically significant. We do not know if sea duck population declines are related to metals or other contaminants.

Ruminant uptake of nickel and other elements from industrial air pollution in the Norwegigan-Russian border area

Concentrations of the elements aluminium, arsenic, cadmium, chromium, cobalt, copper, lead, mercury, nickel, selenium and zinc in liver, and of nickel in kidneys, were studied in reindeer, moose and sheep from South Varanger in eastern Finnmark and comparable districts in western Finnmark, Norway. The study included samples from 31 reindeer, 10 moose and 10 sheep from Jarfjord (South Varanger); 31 reindeer, 27 moose and 15 sheep from Pasvik (South Varanger); and 40 reindeer, 16 moose and 15 sheep from western Finnmark. Levels of arsenic, copper, nickel and selenium were much higher in reindeer from one or both areas in South Varanger than in reindeer from western Finnmark. Levels of chromium, cobalt and zinc were also significantly higher in South Varanger reindeer than in reindeer from the reference area. Within South Varanger the highest levels of these elements were invariably found in the Jarfjord area. For the other elements studied hepatic levels in South Varanger were similar to or lower than in western Finnmark. Also in moose, higher levels of nickel and of selenium (Jarfjord only) were found in the South Varanger samples than in samples from western Finnmark. In sheep, on the other hand, levels in South Varanger samples were similar to levels in western Finnmark for all the elements studied. Comparing the results with reports on pollution of air and vegetation, it was concluded that for all the elements showing higher levels in reindeer and moose from South Varanger compared to the reference areas, the effect most probably was a result of atmospheric transport of industrial pollution from the nearby Russian towns Nikel and Zapoljarnij. The geographical and interspecies differences within the South Varanger samples support this conclusion.

Evaluation of chemopreventive effect of dietary selenium-rich egg on mouse skin tumor induced by 2'-(4-nitrophenoxy)oxirane and 12-O-tetradecanoylphorbol-13-acetate.

Chemoprotective effect of dietary selenium (as sodium selenite or as Se-rich egg) on mouse skin tumor induced by topical application of 2'-(4-nitrophenoxy)oxirane (NPO) as tumor initiator and 12-O-tetradecanoylphorbol-13-acetate (TPA) as tumor promoter was evaluated in relation to the dietary source and levels of selenium. Selenium supplementation (0.3 p.p.m.) to the basal diet (0.07 p.p.m. Se) as sodium selenite or as Se-rich egg brought about a 40 or 37% reduction respectively, in the incidence of papilloma formation at 12 weeks after NPO treatment. Tumor yield (number of papillomas per mouse) at 14 weeks after NPO treatment in the basal diet group, basal diet supplemented with 0.3 p.p.m. Se as sodium selenite group and basal diet supplemented with 0.3 p.p.m. Se as Se-rich egg group were 7.5 +/- 2.1, 2.7 +/- 2.3 and 4.1 +/- 3.5 respectively. Dietary supplementation of 1.0 p.p.m. See as Se-rich egg to the basal diet reduced the incidence and the multiplicity of papillomas during the early phase of promotion (11 weeks) but its antitumor activity decreased thereafter, indicating that the accumulation of tissue selenium above the saturated level may not be beneficial. Selenium concentrations in blood, liver and skin tissue of mice in basal diet group (0.33 +/- 0.02, 0.54 +/- 0.10 and 0.21 +/- 0.03 p.p.m. respectively) increased significantly ( P < 0.05) by the supplementation of 0.3 p.p.m. Se as selenite (0.58 +/- 0.02, 1.17 +/- 0.10 and 0.31 +/- 0.05 p.p.m. respectively), 0.3 p.p.m. Se as Se-rich egg (0.59 +/- 0.02, 1.25 +/- 0.11 and 0.33 +/- 0.06 p.p.m. respectively) and 1.0 p.p.m. Se as Se-rich egg (1.20 +/- 0.05, 2.32 +/- 0.28 and 0.51 +/- 0.01 p.p.m. respectively). Glutathione peroxidase activity in blood of mice of the basal diet group (2.4 +/- 0.4 EU/mg) increased significantly (P < 0.05) by dietary selenium supplementation (3.8 +/- 0.6 EU/mg in 0.3 p.p.m. Selenite; 3.7 +/- 0.8 EU/mg in 0.3 p.p.m. Se as Se-rich egg; 4.9 +/- 0.9 EU/mg in 1/0 p.p.m. Se as Se-rich egg) and the enzyme activities in liver and skin tissue also increased by 0.3 p.p.m. Se (as selenite or Se-rich egg) supplementation, but no further increases in their activities were obtained by 1.0 p.p.m. Se (as Se-rich egg). It is, therefore, concluded that a moderate level of dietary selenium (0.3 p.p.m.) has an efficient chemopreventive activity at the promotional stage of carcinogenesis and that dietary selenium rich egg as well as dietary selenite exerted antitumor activity.

Levels of toxic and essential elements in arctic fox in Svalbard

Concentrations of cadmium, mercury, lead, arsenic, selenium, copper, zinc, manganese and iron in liver, and cadmium in kidneys, were analysed in 95 carcasses of arctic fox (Alopex lagopus) caught in Svalbard during three winter seasons from 1984 through 1986. The hepatic concentration ranges of cadmium, mercury, lead and arsenic were 0.1–2.4, 0.01–2.2, < 0.5–2.9 and 0.01–1.3 μg·g−1 WW, respectively. The range of cadmium concentration in the kidneys was from 0.2 to 13 μg·g−1 WW. Cadmium and mercury concentrations were higher in adult animals than in juveniles. The average concentrations of cadmium and lead were similar to recently published levels in polar bear from Svalbard, but the mercury concentrations were lower. Significant geographical differences were observed between trapping areas. Foxes caught north of Isfjorden had lower levels of liver iron and higher levels of all other elements analysed than those caught south of Isfjorden. The recorded concentrations of heavy metals indicate a moderate degree of exposure, which most likely is of natural origin.

Pb, Cd, As, and Se concentrations in livers of dead wild birds from the Ebro Delta, Spain

Wild bird populations are susceptible to the environmental presence of toxic elements and substances, especially those that are non-degradable and tend to concentrate through the food chain. Monitoring of such substances in selected bird species could be useful to evaluate the health condition of the species involved and to assess contamination in the ecosystem. One of the most important wild bird sanctuaries of Europe, the Ebro Delta, is situated in NE Spain. The Ebro Delta is an alluvial plain of about 32,000 ha. Because of its special hydrological conditions and geographical situation, the Ebro Delta supports an important and diverse bird population, estimated at 180,000 in the winter period, constituting 311 different species. Most of the Ebro Delta's surface is dedicated to agriculture, principally rice, also serving as an excellent wild bird habitat. Accordingly, agricultural pesticides could be a major problem for wildlife. But in the last few decades the Ebro River and the Tarragona coast have also undergone considerable industrial development. The area is now facing environmental threats by industrial activities, and the ecosystem is becoming contaminated with heavy metals, petroleum hydrocarbons and PCBS. Heavy metal concentrations in marine organisms have been reported, but metal and metalloid concentrations inmore » birds have not been available. This study monitors lead (Pb), cadmium (Cd), arsenic (As) and selenium (Se) concentrations in bird livers from diverse trophic levels in the Ebro Delta. Pb, Cd and As are well recognized as toxic elements, while Se, although causing well known deleterious effects for humans and domestic animals, has only recently been recognized as toxic for aquatic birds. The determination of contaminant loads in several avian species would be useful to control and prevent, when possible, pathological conditions derived from toxic levels of these contaminants for wild bird populations living in the Ebro Delta. 10 refs., 2 tabs.« less

Copper deficiency affects selenoglutathione peroxidase and selenodeiodinase activities and antioxidant defense in weanling rats

Copper deficiency has been postulated result in low selenoglutathione peroxidase (Se-GSHPx) activity, secondary to alterations in the antioxidant defense system. Type I iodothyronine 5'-deiodinase contains selenium; because it is not part of the antioxidant defense system its measurement provides a way to evaluate the influence of copper on selenoenzymes independent of the antioxidant system. Weanling rats were fed the control diet (125.9 nmol Cu/g diet), copper-deficient diet (7.9 nmol Cu/g diet), or the control diet restricted to the intake of the deficient rats (restrict-fed), for 21 d. Rats fed the copper-deficient diet had cardiomegaly, low hematocrit values, and low tissue copper concentrations, but normal liver selenium concentrations. Liver and plasma Se-GSHPx activities were lowest in the deficient rats. Non-Se-GSHPx activity was similar between control and copper-deficient groups. Liver selenodeiodinase activity was lowest in the copper-deficient rats; this reduction was functionally significant as evidenced by low plasma 3,3',5-triiodothyronine and high plasma 3,3',5'-triiodothyronine concentrations.

Plasma and liver selenium levels in the rat during supplementation with 0.5, 2, 6, and 15 ppm selenium in drinking water.

Plasma and liver selenium of Wistar rats were determined after 1, 3, and 6 mo supplementation with 0.5, 2, 6, or 15 ppm selenium as sodium selenite in drinking water. Plasma selenium was not different from control values at additional intake of 0.5 ppm but increased above usual levels at higher intakes. A highly significant correlation was observed between the total quantity of selenium ingested and plasma selenium after 1 mo treatment (r = 0.99, p < 0.01), but was less pronounced after 3 and 6 mo (0.94, p < 0.05, and 0.78, p < 0.05, respectively). The decrease in plasma selenium with time of treatment was more pronounced at higher intakes. There was also a highly significant correlation between total selenium intake and liver selenium concentration (r = 0.99, p < 0.01) after 1 mo of treatment, but this time liver selenium did not change with time, and the correlation remained highly significant throughout the investigation. Liver selenium therefore appears as a more sensitive and more representative measure of selenium intake than plasma selenium. Most supplements did not affect body weight and survival of animals, except when the diet was supplemented with 15 ppm for 6 mo; however, alterations in biochemical parameters concerning lipid status and hepatic function were observed at levels above 2.0 ppm.