Effects of zinc, copper, and selenium on placental cadmium transport

The objective of the present study was to evaluate the potential effects of zinc, copper, and selenium on placental cadmium transport. From November 2002 through January 2003, a total of 47 healthy pregnant women from Da-Ye City, Hubei Province in Central China participated in the study. Their age, parity, gestational age, pregnancy history, and lifestyle data were obtained by questionnaire interview. The placental, whole-blood, and cord blood levels of cadmium were determined by inductively coupled plasma mass spectrometer (ICP-MS), whole-blood zinc was measured by flame atomic absorption spectrometry (F-AAS), whole-blood copper by ICP-MS, and selenium was by atomic fluorescence spectrophotometry (AFS). The cord blood cadmium concentration (0.020-1.48 microg/L) was significantly lower than in maternal blood (0.80-25.20 microg/L, p<0.01). The placental cadmium concentration was from 0.082 to 3.97 microg/g dry weight. Multiple linear regression analysis indicated that lower levels of maternal blood copper were significantly associated with higher cadmium concentrations in cord blood. Placental cadmium in women with lower levels of maternal blood zinc was significantly higher than in those with normal zinc levels. The placental cadmium level in women with lower whole-blood selenium was significantly lower than in subjects with normal selenium levels. It was concluded that the essential elements copper, selenium, and zinc might significantly affect placental cadmium transport.     

Mercury,cadmium, zinc,copper and selenium in harbour porpoise (Phocoena phocoena) from West Greenland

Muscle, liver, kidney and skin samples taken from 78 harbour porpoises (Phocoena phocoena) were analysed for mercury, cadmium, zinc, copper and selenium. The highest concentrations of mercury were found in the liver (geometric mean 4.17 g/g wet weight), whilst the highest concentrations of cadmium were in the kidney (g.m. 13.2 g/g ww). The levels of cadmium were more than ten times higher than in harbour porpoises from the North Sea and the British NW coast, whilst the mercury levels were about the same. The importance of the cadmium content in the prey is discussed, but this attempt did not revealed the differences. Very high levels of zinc (g.m. 359 g/g ww) and selenium (g.m. 28.6 g/g ww) were found in skin samples, respectively seven and ten times more than in liver. A significant correlation was found between age and the level of mercury and cadmium in all organs. The concentration of mercury and selenium in liver and skin samples and of cadmium and zinc in kidney samples were highly correlated.     

Zinc,cadmium, mercury and selenium in minke whales,belugas and narwhals from West Greenland

Summary Samples of muscle, liver and kidney from 24 minke whales (Balaenoptera acutorostrata), 43 belugas (Delphinapterus leucas), and 98 narwhals (Monodon monoceros) were analyzed for zinc, cadmium, mercury, and selenium. Highly significant age accumulation of mercury was found. A lower level of significance of age accumulation of cadmium in belugas and narwhals is probably due to the fact that some of the highest cadmium concentrations are in subadults and young adults. The maximum concentrations of cadmium and mercury are very high: 1.68, 73.7, and 125 g cadmium, and 9.88, 42.8, and 4.61 g mercury per g wet weight of narwhal muscle, liver and kidney, respectively. The cadmium concentrations are correlated in the three organs, as are mercury and to a lesser extent selenium concentrations. The concentrations of mercury and selenium in liver are highly correlated.     

Determination of iron, copper, zinc, magnesium and selenium in plasma and erythrocytes in neurosurgical patients.

A direct method for determination of Fe, Cu, Zn, Mg and Se in erythrocytes was developed. The aim of the present study was to establish a method for examining perioperative levels of the above mentioned elements simultaneously in erythrocytes and plasma by atomic absorption spectrophotometry in 11 patients undergoing neurosurgery for acute spinal nerve compressions because of intervertebral disk prolapses. Reference values for erythrocytes were 11.49 +/- 3.48 mmol/mmol Hb; 0.82 +/- 0.087 mmol/mmol Hb; 9.01 +/- 2.20 mmol/mmol Hb; 0.104 +/- 0.032 mmol/mmol Hb; 0.07 +/- 0.050 mmol/mmol Hb for iron, copper, zinc, magnesium, and selenium, respectively. Postoperative erythrocyte concentrations did not differ significantly compared to those obtained preoperatively and remained within the reference ranges perioperatively. For plasma the following reference values were used: 19.0 +/- 8.0 mmol/l (Fe); 20.1 +/- 8.2 mmol/l (Cu); 15.4 +/- 4.6 mmol/l (Zn); 0.9 +/- 0.15 mmol/l (Mg); 1.02 +/- 0.3 mmol/l (Se). There was a significant decrease in the concentration of copper in plasma (13.41 +/- 3.46 mmol/l, p < 0.1) and zinc (10.73 +/- 2.73 mmol/l, p < 0.1) immediately postoperative, iron (10.56 +/- 3.91 mmol/l, p < 0.1) and zinc on day 1 (11.28 +/- 1.88 mmol/l, p < 0.10), and a significant postoperative increase of copper on day 5 (18.81 +/- 3.97 mmol/l, p < 0.1), postoperatively. The mean plasma concentrations of iron, copper, zinc magnesium and selenium remained within the reference ranges during the entire period.     

Selenium, zinc, and copper concentrations in the blood and milk of lactating women

The aim of the study was to determine Se, Zn, and Cu concentrations in blood plasma and milk of lactating women from central Poland who were in different stages of lactation and to investigate the relationship between the content of trace elements in mothers’ blood and concentrations of microelements in their milk. Se and Zn concentrations in blood plasma of mothers were the lowest and Cu was the highest on the first 4 d of lactation (colostrum, n=43) and were found to be 34.9±11.8 μg/L, 0.51±0.13 mg/L, and 1.70±0.55 mg/L, respectively. The highest plasma level of Se and Zn and the lowest content of Cu could be observed between d 10 and 30 of lactation (mature milk, n=41), and were found to be 54.3±14.6 μg/L for Se (p<0.001), 0.76±0.20 mg/L for Zn (p<0.001), and 1.03±0.30 mg/L (p<0.001) for Cu. The results of Se, Zn, and Cu determination in breast milk samples demonstrate a pattern of decline in their concentration with advancing stages of lactation. We found out that Se, Zn, and Cu concentrations were the highest in colostrum (n=43) and amounted to 24.8±10.1 μg/L, 8.2±2.8 mg/L, and 0.45±0.11 mg/L, respectively. The content of all determined microelements declined significantly during the time of lactation. Statistically significant linear correlation was found between concentrations of Zn in blood plasma and milk in the first stage of lactation. Weak but statistically significant linear correlations were also found between plasma Se content in plasma and in transitional and mature milk of breast-feeding women.     

Leukocyte selenium, zinc, and copper concentrations in preeclamptic and normotensive pregnant women

Preeclampsia is an important cause of maternal and perinatal mortality worldwide. The etiology of this relatively common medical complication of pregnancy, however, remains unknown. We studied the relationship between maternal leukocyte selenium, zinc, and copper concentrations and the risk of preeclampsia in a large hospital-based case-control study. One hundred seventy-one women with proteinuric pregnancy-induced hypertension (with or without seizures) comprised the case group. Controls were 184 normotensive pregnant women. Leukocytes were separated from blood samples collected during the patients’ postpartum labor and delivery admission. Leukocyte concentrations for the three cations were measured by inductively coupled plasma-mass spectrometry (ICP-MS). Concentrations for each cation were reported as micrograms per gram of total protein. Women with preeclampsia had significantly higher median leukocyte selenium concentrations than normotensive controls (3.23 vs 2.80 μg/g total protein, p<0.0001). Median leukocyte zinc concentrations were 31% higher in preeclamptics as compared with controls (179.15 vs 136.44 μg/g total protein, p<0.0001). Although median leukocyte copper concentrations were slightly higher for cases than controls, this difference did not reach statistical significance (17.72 vs 17.00 μg/g total protein, p=0.468). There was evidence of a linear increase in risk of preeclampsia with increasing concentrations of selenium and zinc. The relative risk for preeclampsia was 3.38 (adjusted odds ratio [OR]=3.38, 95% confidence interval [CI]=1.53–7.54) among women in the highest quartile of the control selenium distribution compared with women in the lowest quartile. The corresponding relative risk and 95% CI for preeclampsia was 5.30 (2.45–11.44) for women in the highest quartile of the control zinc distribution compared with women in the lowest quartile. There was no clear pattern of a linear trend in risk with increasing concentration of leukocyte copper concentrations (adjusted for linear trend in risk =0.299). Our results are consistent with some previous reports. Prospective studies are needed to determine whether observed alterations in selenium and zinc concentrations precede preeclampsia or whether the differences may be attributed to preeclampsia-related alterations in maternal and fetal-placental trace metal metabolism.     

Beneficial effect of goat milk on bioavailability of copper, zinc and selenium in rats

We studied the effects of dietary inclusion of freeze-dried goat and cow milk on the utilization of copper, zinc and selenium, and on the metabolic fate of copper and zinc, in rats using a standard (non-milk) control diet recommended by the American Institute of Nutrition and diets based on goat or cow milk. For animals given the goat milk diet, the apparent digestibility coefficient (ADC) of copper is similar to that obtained with the standard diet and higher than that in animals given the cow milk diet. The copper balance was higher among the rats given the goat milk and the standard diets than among those given cow milk. The ADC and retention of zinc and selenium were higher for the goat milk diet than for the other two diets. The copper content in the kidneys and in the femur was greater when the animals consumed a goat milk diet than a cow milk diet. Zn deposits in femur, testes, liver, kidney, heart and longissimus dorsi muscle were greatest with the goat-milk diet, followed by the standard diet and were lowest for the rats given cow-milk diet. This study shows that the goat-milk has an important and beneficial effect on the bioavailability of copper, zinc and selenium.     

Zinc,cadmium, mercury and selenium in polar bears (Ursus maritimus) from Central East Greenland

Muscle, liver, and kidney tissues from 38 polar bears (Ursus maritimus) caught in the Scoresby Sound area, Central East Greenland, were analysed for zinc, cadmium, mercury and selenium. In general, cadmium concentrations were low in muscle, liver and kidney tissue, with geometric means (g.m.) of 0.022 (range: <0.015–0.085), 0.841 (range: 0.092–3.29) and 13.1 (range: 1.04–115) g Cd/g wet weight (ww) respectively. This finding can be explained by low cadmium levels in the blubber of ringed seals. The concentration of mercury in muscle tissue was low (g.m. 0.071; range: 0.039–0.193 g Hg/g ww), whereas concentrations in liver and kidney tissue were relatively high (liver: g.m. 7.87; range: 1.35–24.8 g Hg/g ww, and kidney: g.m. 15.2; range: 1.59–66.6 g Hg/g ww). Mercury and cadmium were positively correlated with age in liver and kidney. Zinc was positively correlated with age in kidney, and selenium was correlated with age in liver. Contrary to other marine mammals, polar bears had higher mercury levels in the kidneys than in the liver. In all three tissues polar bears had significantly lower cadmium levels than ringed seals from the same area. Mercury levels were likewise significantly lower in the muscle tissue of polar bears than in ringed seals, whereas levels in the liver and kidney were significantly higher. The previous geographic trend for cadmium and mercury found in Canadian polar bears could be extended to cover East Greenland as well. Hence cadmium levels were higher in Greenland than in Canada, while the opposite was the case for mercury. Greenland polar bears had higher mercury and cadmium contents in livers and kidneys than polar bears from Svalbard. The mercury levels in muscle and liver tissue from polar bears from East Greenland were twice as high as found in bears from western Alaska, but half the levels found in northern Alaska. Cadmium and zinc were partially correlated in kidney tissue, and this was found for mercury and selenium as well. Cadmium and zinc showed molar ratios close to unity with the highest concentrations occurring in kidney tissue, while the levels of zinc exceeded cadmium in muscle and liver tissue by up to several decades. Mercury and selenium showed molar ratios close to unity in liver and kidneys.     

Leptin in bovine colostrum and milk.

We studied leptin content in bovine colostrum, milk and plasma during the first month of lactation, and investigated relationships between selected milk components and milk leptin in five multiparous dairy cows. Colostrum/milk yield and composition were measured on days 0, 10, 20, and 30 of lactation. Leptin was assayed using a multi-species leptin RIA kit. Leptin concentration was 56 % lower in mature milk (day 10) than colostrum (13.90 vs. 6.14 microg/l; p < 0.001), but remained steady over the twenty days afterwards. Daily secretion of leptin into mature milk was 28 % lower than into colostrum (173.2 microg/d vs. 220.0 microg/d; p = 0.09) notwithstanding an 80 % increase in production. Colostrum and milk leptin levels correlated with fat (0.90; p < 0.001) and choline phospholipid (0.76; p < 0.05). Plasma and milk leptin decreased during the first month, but remained higher in milk, and highest in colostrum. Thus, leptin is present in large quantities in colostrum, less so and more variably in untreated milk, and is likely to be decreased in skimmed milk. These findings have implications for the use of untreated milk and colostrum-based (functional) food products.     

Effects of nationwide addition of selenium to fertilizers on foods,and animal and human health in Finland: From deficiency to optimal selenium status of the population

Despite different geological features the Nordic countries are generally selenium-poor areas. In each country various factors such as food importation and life-style determine the selenium (Se) intake. Due to an extremely low Se intake in the 1970s in Finland, 0.025 mg/day, an official decision was made in 1984 to supplement multinutrient fertilizers with Se in the chemical form of sodium selenate. Almost all fertilizers used in Finland since 1985 have contained Se. Currently all crop fertilizers contain 15 mg Se/kg. Finland is still the only country to take this country-wide measure.In a national monitoring programme, sampling of cereals, basic foodstuffs, feeds, fertilizers, soils, and human tissues has been carried out annually since 1985 by four governmental research organizations. Sampling of foods has been done four times per year and human blood has been obtained annually from the same (n = 60) adults. The accuracy of analyses has been verified by annual interlaboratory quality control. During this programme the selenium concentration of spring cereals has increased on average 15-fold compared with the level before the Se fertilization. The mean increase in the Se concentration in beef, pork and milk was 6-, 2- and 3-fold. In terms of Se, organically grown foods of plant origin are generally comparable to products produced before the Se supplementation of fertilizers. Milk from organically fed cows is 50% lower in Se than the usual milk. The average dietary human intake increased from 0.04 mg Se/day/10 MJ in 1985 to a present plateau of 0.08 mg Se/day/10 MJ, which is well above the current nutrition recommendations. Foods of animal origin contribute over 70% of the total daily Se intake. The mean human plasma Se concentration increased from 0.89 μmol/L to a general level of 1.40 μmol/L that can be considered to be an optimal status. The absence of Se deficiency diseases and a reference population have made conclusions on the impact on human health difficult. However, the rates of cardiovascular diseases and cancers have remained similar during the pre- and post-supplementation indicating medical and life-style factors to be much stronger determinants than Se. The nationwide supplementation of fertilizers with sodium selenate is shown to be effective and safe in increasing the Se intake of the whole population. Also, the health of animals has improved.     

Association Between Zinc, Copper, and Iron Concentrations in Breast Milk and Growth of Healthy Infants in Tabriz, Iran

The aims of this study were to determine the effect of breast milk zinc, copper, and iron concentrations on infants’ growth and their possible correlations with maternal dietary intake. Milk samples and information on food intake were collected from 182 lactating women. Concentrations of zinc, copper, and iron in milk were analyzed using atomic absorption spectrophotometry. The infant’s weight for age Z-score (WAZ) and height for age Z-score (HAZ) were calculated. The mean milk zinc, copper, and iron concentrations were 1.85?±?0.5, 0.53?±?0.3, and 0.85?±?0.2 mg/l, respectively. Only zinc mean level was lower than the recommended range. Association between zinc, copper, and iron concentrations of milk and WAZ or HAZ of infants were not significant. However, the WAZ of infants whose mothers' milk zinc was more than 2 mg/l was significantly (P?<?0.039) higher than for others. The mean dietary zinc (5.31?±?2.3 mg/day) and copper (1.16?±?0.7 mg/day) intake of mothers was significantly less than the required daily intake (RDA) recommendations (P?<?0.05). The mean dietary iron intake (11.8?±?8.2 mg/day) was significantly higher than RDA recommendation (P?<?0.001). No significant association was found between maternal mean dietary zinc, copper, and iron intakes with their concentrations in milk. Dietary consultation or/and zinc supplementation is suggested for lactating women and infants.     

Concentrations of cadmium,lead, selenium,and zinc in human blood and seminal plasma

The concentrations of cadmium, lead, selenium, and zinc in blood and seminal plasma were determined in 76 Singapore males. Except for zinc, the concentrations were generally higher in blood than in seminal plasma (cadmium, 1.31 μg/L vs 0.61 μg/L; lead, 82.6 μg/L vs 12.4 μg/L, and selenium, 163.6 μg/L vs 71.5 μg/L). The mean concentration of zinc in seminal plasma was more than 30 times higher than in blood (202 mg/L vs 6.2 mg/L). Significant positive correlations were found between the concentrations in blood and seminal plasma for the two essential trace elements: selenium (r=0.45,p<0.001) and zinc (r=0.25,p<0.05). However, no relationships were found between the concentrations in blood and seminal plasma for two toxic metals (cadmium and lead). Significant inverse correlations were observed between Cd and Zn (r=−0.40,p<0.01), and Pb and Se (r=−0.32,p<0.05) in blood, whereas significant positive correlations were noted between Cd and Se (r=0.45,p<0.01), Cd and Zn (r=0.35,p<0.05), and Se and Zn (r=0.57,p<0.001) in seminal plasma. The physiological significance of these relationships are also discussed in this paper.     

Trace Element Levels in Hashimoto Thyroiditis Patients with Subclinical Hypothyroidism

The present study was conducted to evaluate the serum copper, zinc, magnesium, and selenium levels in patients with subclinical hypothyroidism in the iodine-rich region of Ankara, Turkey. The effects of hormone replacement therapy on these elements were also studied in these patients. Basal levels of selenium and iron in patients were significantly lower than control group (67.7 +/- 10.4 vs. 83.7 +/- 17.3 microg/dl, p = 0.02; 55.7 +/- 38 vs 275.7 +/- 24, P = 0.03 microg/dl). Serum magnesium levels were significantly higher in patient group (2.16 +/- 0.31 vs 1.95 +/- 0.13 mg/dl, P < 0.0001). There was a correlation between selenium levels with hsCRP (r = -0.408, p = 0.007). HsCRP levels in patients with selenium levels <80 microg/l (n = 31) was significantly higher than hsCRP levels in patients with selenium levels >80 microg/l (n = 12; 1.99 +/- 1.0; 1.02 +/- 0.9, p = 0.014). None of these biochemical risk factors and trace elements have changed after euthyroidism in patients with SH when compared to pretreatment levels. Selenium deficiency may contribute to cardiovascular disease risk in these patients.     

Estimation of Mineral and Trace Element Profile in Bubaline Milk Affected with Subclinical Mastitis

The milk samples from buffaloes of Murrah breed at mid lactation stage, reared at an organised dairy farm, were screened for subclinical mastitis based on bacteriological examination and somatic cell count following International Dairy Federation criteria. Milk samples from subclinical mastitis infected and healthy buffaloes were analysed to evaluate physicochemical alterations in terms of protein, fat, pH, electrical conductivity, chloride, minerals (sodium, potassium and calcium) and trace elements (iron, zinc, copper and selenium). In the present study, protein, fat, zinc, iron, calcium and selenium content was significantly lower (P < 0.001), while pH and electrical conductivity were significantly higher in mastitic milk as compared to normal milk. Concentration of electrolytes mainly sodium and chloride significantly increased with higher somatic cell count in mastitic milk and to maintain osmolality; potassium levels decreased proportionately. Correlation matrix revealed significantly positive interdependences of somatic cell count with pH, electrical conductivity, sodium and chloride. However, protein, fat, calcium and potassium were correlated negatively with elevated somatic cell count in mastitic milk. It is concluded that udder infections resulting in elevated somatic cells may alter the mineral and trace element profile of milk, and magnitude of changes may have diagnostic and prognostic value.     

Interactive Effects of Selenium and Cadmium on Mammary Tumor Development and Growth in MMTV-Infected Female Mice. A Model Study on the Roles of Cadmium and Selenium in Human Breast Cancer

Previous studies demonstrated that the age-corrected breast cancer mortalities in different countries are inversely correlated with the per-capita dietary intakes of selenium and directly with the estimated intakes of cadmium, zinc, and chromium, suggesting that the anticarcinogenic properties of selenium are counteracted by these elements. The tumor-preventative effects of selenium and the converse effects zinc and chromium have already been confirmed experimentally in studies with female inbred C3H mice carrying murine mammary tumor virus (MMTV). Using the same model of human breast cancer, it is now demonstrated that cadmium abolishes the cancer-protecting effects of selenium. In addition, cadmium was also found to interact with zinc, copper, and chromium. At 1.4 ppm in the drinking water, cadmium caused a significant depletion of zinc in vital organs such as the liver, which is held responsible for a delay of the appearance of the mammary tumors by 4 months and their slower growth rates relative to the Cd-unexposed controls. The results of the present study are relevant to human breast cancer prevention as selenium counteracts the effects of cadmium.     

Serum and hair levels of zinc, selenium, iron, and copper in children with iron-deficiency anemia

In the present study, the serum and hair levels of zinc, selenium, and copper were determined in children with iron-deficiency anemia (IDA). A total of 52 anemic children aged 1–4 yr constituted the study group. Fortysix healthy children acted as controls. The copper and zinc levels were measured with an atomic absorption spectrophometer. Serum and hair selenium was determined by a spectroflourometric method. The serum zinc and selenium concentrations in the IDA group were found to be significantly lower and serum copper significantly higher than those in the controls (p<0.05). Lower iron, zinc, and selenium concentrations (p<0.001) but not copper were found in hair (p>0.05).     

Cadmium induced lipid peroxidation in rat testes and protection by selenium

The main goal of this study was to investigate the role of cadmium in the promotion of lipid peroxidation in the homogenates of rat testes and the effect of selenium on lipid peroxidation in testes of rats after cadmium injection. Treatment of rats with cadmium resulted in a time- and dose-related accumulation of the metal ions in testes. The concentrations of cadmium, copper, zinc, selenium and iron in the tissues were determined by an atomic absorption spectrophotometer and lipid peroxidation in testes was measured by a spectrophotometer. Cadmium produced enhanced lipid peroxidation in testes. These cadmium-induced changes were accompanied by a significant increase of iron and copper, and a decrease of zinc in testes. Concurrent treatment with selenium and cadmium reduced the cadmium-induced alterations in lipid peroxidation and essential metal levels. Data suggest that lipid peroxidation was associated with cadmium toxicity in testes and that the addition of selenium was found to be effective in attenuation of this effect.     

Serum levels of selenium, manganese, copper, and iron in colorectal cancer patients

This article describes a study in which four trace elements (Se, Mn, Cu, and Fe) were analyzed in the blood serum of the patients with colorectal cancer from the Moravian region of the Czech Republic. Atomic absorption spectrometry with graphite furnace atomization was used for analysis of selenium and manganese and with flame atomization for analysis of copper and iron. The observed serum concentrations in adenocarcinoma colorectal patients of selenium were significantly lower (41.8 ± 11.6 μg/L) and those of manganese (16.3 ± 4.5 μg/L) and iron (2.89 ± 1.23 mg/L) were significantly higher as compared to the age-matched control group. Copper serum content (0.95 ± 0.28 mg/L) did not significantly differ as compared to healthy population.     

The effect of nationwide selenium enrichment of fertilizers on selenium status of healthy finnish medical students living in south western Finland

In Finland commercial fertilizers have been enriched with sodium selenate since July 1, 1984 in order to compensate for the poor selenium content of the soil. Fertilizers that are used for the production of hay and fodder were supplemented with 6 mg/kg of selenium, whereas fertilizers used for the production of cereals were supplemented with a higher dose, 16 mg/kg fertilizer. The effects of selenium fertilization were first seen in dairy products in June 1985, and from the beginning of August 1985, the effect was evident also in wheat flour, beef, and bovine liver. In this study the selenium status of 108 healthy young adults has been systematically documented since November 1985, at which time the mean selenium serum level (S-Se) was 1.05 umol/L. A steady increase was observed until November 1989, when the maximum level, with a mean of S-Se 1.6 umol/L was reached. After that, a slight decrease has occurred. The mean serum selenium level in autumn 1991 in a new group of 35 students was 1.58 umol/L. This decrease can be explained by the high amount of imported cereals in 1988 and 1989, which was reflected also in the serum selenium levels. The glutathione peroxidase activity in erythrocytes in 1989–1990 was at the same level as in 1985 and 1986.     

Dietary selenium supplementation prolongs pentobarbital induced hypnosis

The present studies characterized the influence of dietary selenium (Na2SeO3) on the duration of pentobarbital (PB) induced hypnosis (sleep) in the rat. Rats were fed semipurified diets varying from 0.01 to 2.0 mg Se/kg for up to 4 weeks. Consumption of diets containing 1.0 and 2.0 mg Se/kg significantly prolonged PB induced hypnosis. Hepatic selenium, but not hepatic glutathione peroxidase activity, correlated with the length of PB induced hypnosis. The prolongation of hypnosis caused by diets containing 1.0 mg Se/kg was substantially reduced or eliminated by repeated exposure to PB. Although single exposure to increasing quantities of PB (60-100 mg/kg body weight) led to a progressive increase in sleep duration, the proportional increase caused by supplemental selenium (2.0 vs 0.1 microg Se/g) remained relatively constant (approximately 25%). Increasing maturity was inversely related to the duration of PB induced hypnosis, regardless of dietary selenium provided. Consumption of the 2.0 mg Se/kg diet prolonged PB induced hypnosis to a greater degree in immature than in mature rats (P < 0.05). Consumption of the selenium enriched diet (2 microg Se/g) resulted in an increase in cytochrome 2B, but had no effect on cytochrome 1A compared to controls (0.1 microg Se/g). Pretreatment of rats with P450 enzymes activators (i.e., PB, Aroclor 1254, or 3-methylcholanthrene) shortened the duration of PB induced sleep and masked the effects of dietary selenium. The current studies document that dietary selenium can influence the response to pentobarbital induced hypnosis and likely relates to changes in drug detoxification enzymes.