Liver selenium and testis phospholipid hydroperoxide glutathione peroxidase are associated with growth during selenium repletion of second-generation Se-deficient male rats

We have previously shown that changes in glutathione peroxidase-1 (GPX1; H2O2:oxidoreductase, EC 1.11.1.9), plasma thyroid hormone and glutathione-S-transferase were not associated with changes in growth observed in second-generation (F2) severely Se-deficient rats; we also found that liver phospholipid hydroperoxide glutathione peroxidase (GPX4; EC 1.11.1.12) activity falls in first-generation (F1) Se-deficient rats to 41% of levels in Se-adequate rats. The purposes of this study were to determine the effect of F2 Se deficiency on GPX4 and to detect early changes in Se parameters associated with growth after single, small Se injections. Se-deficient male F2 weanling rats were randomly divided into two groups and fed a Se-deficient crystalline amino acid (0.003 microg Se/g diet; -Se) diet or that diet supplemented for 14 d with 0.2 microg Se/g diet (+Se) as Na2SeO3. Growth of -Se rats was 55% of the rate of +Se rats. Liver Se, GPX1 activity, GPX4 activity and testis GPX4 activity in -Se rats at 14 d were 1, 2, 23 and 13%, respectively, of levels in +Se rats. In a series of experiments, additional F2 male weanling rats were fed the -Se diet for 14 d and then were given an intraperitoneal single saline injection of 0, 1 or 5 microg Se/100 g body weight (BW) as Na2SeO3 and killed 1 or 7 d later. Rats injected with 1 or 5 microg Se/100 g BW grew 36 or 48%, respectively, above the rate of saline-injected rats. Liver Se concentration increased 367% and testis GPX4 activity doubled in rats 1 d after injection of 1 microg Se/100 g BW compared with saline-injected rats; these parameters were further elevated with 5 microg Se/100 g BW injections. Increases in liver Se and testis GPX4 activity were the parameters best associated with improved growth after Se injection, but the molecular role for Se in growth remains unclear.     

Selenium regulation of classical glutathione peroxidase expression requires the 3' untranslated region in Chinese hamster ovary cells

Classical glutathione peroxidase (GPX) mRNA levels fall dramatically in selenium (Se)-deficient animals, but it is not known whether this mechanism is related to the mRNA 3' untranslated region (3'UTR) sequences that have been shown to direct Se incorporation. In this study, we used recombinant GPX constructs to investigate the role of the GPX 3'UTR in Se regulation of GPX mRNA levels in Chinese hamster ovary (CHO) cells. The CHO cells were transfected with GPX (pRc/GPX), GPX lacking the 3'UTR (pRc/Delta3'UTR) or the pRc/CMV vector alone, and GPX activity and GPX mRNA levels were determined in stable transfectants grown in low Se basal medium with a range of added Se concentrations. We identified two pRc/GPX transfectants with significantly elevated GPX activity levels compared with pRc/CMV transfectants. The elevated GPX expression did not dramatically shift the amount of Se that was sufficient for GPX activity to reach the Se-adequate plateau level (100 nmol/L added Se). As expected, GPX activity was not significantly different when pRc/Delta3'UTR transfectants were compared with pRc/CMV control transfectants. Among the wild type and transfected CHO cells, Se-deficient GPX activity levels averaged 35 +/- 5% of Se-adequate levels. Selenium-deficient levels of endogenous GPX mRNA as well as recombinant pRc/GPX mRNA averaged 54-58% of Se-adequate levels; 3-4 nmol/L added Se was sufficient for maximal GPX mRNA levels. In contrast, pRc/Delta3'UTR mRNA levels in the unsupplemented cells remained at Se-adequate levels and showed no distinct Se regulation. These studies demonstrate that the GPX 3'UTR is necessary for Se regulation of GPX mRNA levels in addition to its role in Se incorporation.     

Cis-acting elements are required for selenium regulation of glutathione peroxidase-1 mRNA levels

Classical glutathione peroxidase (GPX1) mRNA levels can decrease to less than 10% in selenium (Se)-deficient rat liver. The cis-acting nucleic acid sequence requirements for Se regulation of GPX1 mRNA levels were studied by transfecting Chinese hamster ovary (CHO) cells with GPX1 DNA constructs in which specific regions of the GPX1 gene were mutated, deleted, or replaced by comparable regions from unregulated genes such as phospholipid hydroperoxide glutathione peroxidase (GPX4). For each construct, stable transfectants were pooled two weeks after transfection, divided into Se-deficient (2 nM Se) or Se-adequate (200 nM Se) medium, and grown for an additional four days. On day of harvest, Se-deficient GPX1 and GPX4 activities averaged 13 +/- 2% and 15 +/- 2% of Se adequate levels, confirming that cellular Se status was dramatically altered by Se supplementation. RNA was isolated from replicate plates of cells and transfected mRNA levels were specifically determined by RNase protection assay. Analysis of chimeric GPX1/GPX4 constructs showed that the GPX4 3'-UTR can completely replace the GPX1 3'-UTR in Se regulation of GPX1 mRNA. We did not find any GPX1 coding regions that could be replaced by the corresponding GPX4 coding regions without diminishing or eliminating Se regulation of the transfected GPX1 mRNA. Further analysis of the GPX1 coding region demonstrated that the GPX1 Sec codon (UGA) and the GPX1 intron sequences are required for full Se regulation of transfected GPX1 mRNA levels. Mutations that moved the GPX1 Sec codon to three different positions within the GPX1 coding region suggest that the mechanism for Se regulation of GPX1 mRNA requires a Sec codon within exon 1. Lastly, we found that addition of the GPX1 3'-UTR to beta-globin mRNA can convey significant Se regulation to beta-globin mRNA levels when a UGA codon is placed within exon 1. We conclude that Se regulation of GPX1 mRNA requires a functional selenocysteine insertion sequence (SECIS) in the 3'-UTR and a Sec codon followed by an intron.     

Selenium regulates gene expression for estrogen sulfotransferase and alpha 2U-globulin in rat liver

Dietary intake of the essential trace element selenium (Se) regulates expression of genes for selenoproteins and certain non-Se-containing proteins. However, these proteins do not account for all of Se's biological effects. The objective of this work was to identify additional genes whose expression is regulated by Se. Identification of these genes may reveal new functions for Se or define mechanisms for its biological effects. Weanling male Sprague-Dawley rats were fed a Torula yeast-based Se-deficient basal diet or the same diet supplemented with 0.5 mg Se/kg diet as sodium selenite for 13 weeks. Total RNA was used as template for RNA fingerprinting. Two differentially expressed cDNA fragments were identified and cloned. The first had 99% nucleotide identity with rat liver estrogen sulfotransferase (EST) isoform-6. The second had 99% nucleotide sequence identity with rat liver alpha 2u-globulin. The mRNA levels for both were markedly reduced in Se deficiency. Laser densitometry showed that EST mRNA in Se deficiency was 7.3% of that in Se-adequate rat liver. The level of alpha 2u-globulin mRNA in Se-deficient rat liver was only 12.6% of that in Se-adequate rat liver. These results indicate that dietary Se may play a role in steroid hormone metabolism in rat liver.     

A review of relationships between active living and determinants of health

To clarify the relationship between selenium (Se) deficiency and functional disorders, the authors determined the Se concentration, anti-oxidant enzyme activity, and other parameters in rats fed a Se-deficient diet. Rats fed the Se-deficient diet showed a decrease in Se concentration and glutathione peroxidase (GSH-Px) activity in plasma, erythrocytes, heart, liver, and skeletal muscle from the first week after the initiation of the diet, an increase in heart lipid peroxide concentration from the second week, and an increase in liver glutathione S-transferase activity from the fourth week. From the twelfth week, a decrease in the growth rate in the rats fed the Se-deficient diet was observed. In spite of this growth impairment, no changes in electrocardiogram, muscle tone, degree of hemolysis, plasma biochemistry, or hematological values were detected. In summary, the authors found that a reduction of body Se is easily induced, but that the appearance of functional disorders following Se deficiency is difficult to detect in rats.     

Modulation of embryonic glutathione peroxidase activity and phenytoin teratogenicity by dietary deprivation of selenium in CD-1 mice

Selenium (Se)-dependent and -independent glutathione (GSH) peroxidases detoxify H2O2 and lipid hydroperoxides, which may mediate the teratogenicity of phenytoin and related xenobiotics. To test this hypothesis, CD-1 mice were placed on Se-deficient diets for 15, 25 or 40 days and bred so that the day of analysis corresponded to gestational day 11. In Se-replete control animals, embryonic peroxidase activities were only 5% of activities in maternal liver (P < .05). After 15 days of Se deprivation, maternal activities for H2O2 (reflecting Se-dependent peroxidase) and cumene hydroperoxide (CmOOH) (reflecting both Se-dependent and -independent peroxidases) were reduced to 20% (P < .05) and 35% of controls, respectively. At this time, the incidence of fetal cleft palates initiated by phenytoin (55 mg/kg intraperitoneally on gestational days 11, 12 and 13) was doubled, from 12% to 25% (P < .05). Selenite rescue (Na2SeO3, 350 micrograms/kg intraperitoneally on day 9) restored maternal and embryonic peroxidase activities and completely inhibited phenytoin-initiated postpartum lethality and fetal resorptions in animals that had been Se depleted for 15 days. After 40 days of Se deprivation, maternal and embryonic peroxidase/H2O2 activities were reduced to < 1% and 27% of Se-replete controls, respectively. In contrast, maternal peroxidase/CmOOH activity was increased to 70% of controls, reflecting induction of Se-independent peroxidase, compared with that with 15 days' depletion. Phenytoin-initiated cleft palates with 40 days' depletion appeared to be reduced (16%) compared with Se-replete controls (24%) (P < .07). In 40-day Se-depleted animals given selenite rescue, the 10% incidence of cleft palates was significantly lower than that in the 40-day Se-replete group (24%) but not the Se-depleted group (16%). This is the first demonstration of reduced Se-dependent GSH peroxidase activities in embryonic tissues with dietary Se-deprivation. The results implicate reactive oxygen species and lipid hydroperoxides in the mechanism of phenytoin teratogenicity and suggest that GSH peroxidases are important embryoprotective enzymes.     

Molecular cDNA cloning and tissue distribution of mRNA encoding a novel ATP-binding cassette (ABC) half-transporter

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.     

Double-positive thymocytes resistant to antigen-MHC-induced negative selection lack active caspase

The aim of the current study was to elucidate the synergism of dietary calcium restriction and exhaustive exercise in the antioxidant enzyme system of rat soleus muscle, and to investigate the involvement of neutrophils in exercise-induced muscle damage. Forty-eight male Wistar rats were assigned to the following groups: control (C) or calcium-restricted [1 month (1 M) or 3 months (3 M)]. Each group was subdivided into acutely exercised or non-exercised groups. Soleus muscle from each rat was analysed to determine the levels of antioxidant enzymes [Mn-superoxide dismutase (SOD), Cu, Zn-SOD, glutathione peroxidase (GPX), and catalase (CAT)]. Dietary calcium restriction resulted in calcium deficiency and upregulated the antioxidant enzymes examined except GPX. Conversely, exhaustive exercise significantly decreased GPX and CAT, but not SODs activities in the calcium-restricted (1 M and/or 3 M) rats. Contents of immunoreactive Mn-SOD and Cu,Zn-SOD were only increased in the 3 M rats. During calcium restriction, the mRNA expression of both forms of SOD showed initial upregulation, followed by downregulation. Exhaustive exercise significantly increased the mRNA expressions only in the 3 M rats. Moreover, exhaustive exercise markedly increased myeloperoxidase activity in soleus muscles from the 1 M and 3 M rats compared with the C rats, and significantly enhanced the ability of neutrophils to generate superoxide in the 3 M rats. The results demonstrate that dietary calcium restriction upregulates certain antioxidant enzyme activities in rat soleus muscle, indicating an enhanced resistance to potential increases in intracellular reactive oxygen species. The results also suggest that exhaustive exercise may cause oxidative damage in soleus muscle of calcium-deficient rats through the activation of neutrophils.     

Some physicochemical and enzymic properties of selenium-containing abzyme

We successfully prepared the Se-containing abzyme (Se-abzyme) with glutathione peroxidase (GPX) activity and further studied its physicochemical and enzymic properties and stabilities. Data showed that the isoelectric point of the abzyme was 6.95-7.08, and its molecular weight was 158 KD. The ranges of optimum pH and temperature of the Se-abzyme were wider than the native GPX. The store stability of the abzyme was higher than the native GPX. The Se content in the abzyme was found to be 5 mol Se/mol abzyme by X-ray photoelectron spectrum, and binding constant 1.11 x 10(7)M-1 by using ELISA method. The Se-abzyme was inhibited competitively by dithiobis(2-nitrobenzoic acid) (DTNB), and inhibition constant was determined to be 1.25 x 10(-3)M-1.     

Selenium-dependent and selenium-non-dependent glutathione peroxidase in patients with Balkan endemic nephropathy

We studied the activity of erythrocyte selenium (Se)-dependent, Se-non-dependent glutathione peroxidase (GSH-Px), and superoxide dismutase (SOD) in uremic patients (UP) in clinically healthy members from families affected with Balkan nephropathy (HMF/BEN) and in healthy volunteers from endemic settlements (control group). The SOD activity was not significantly different in the groups studied and the Se-non-dependent GSH-Px activity in HMF/BEN and UP was not different from the control group. However, the activity of Se-dependent GSH-Px in UP was lower compared with the control group, whereas the mean value of the Se-dependent GSH-Px activity in HMF/BEN was not significantly different when compared with the other two investigated groups.     

Levels of major selenoproteins in T cells decrease during HIV infection and low molecular mass selenium compounds increase

It has been observed previously that plasma selenium and glutathione levels are subnormal in HIV-infected individuals, and plasma glutathione peroxidase activity is decreased. Under these conditions the survival rate of AIDS patients is reduced significantly. In the present study, using 75Se-labeled human Jurkat T cells, we show that the levels of four 75Se-containing proteins are lower in HIV-infected cell populations than in uninfected cells. These major selenoproteins migrated as 57-, 26-, 21-, and 15-kDa species on SDS/PAGE gels. In our earlier studies, the 57-kDa protein was purified from T cells and identified as a subunit of thioredoxin reductase. The 26- and 21-kDa proteins were identified in immunoblot assays as the glutathione peroxidase (cGPX or GPX1) subunit and phospholipid hydroperoxide glutathione peroxidase (PHGPX or GPX4), respectively. We recently purified the 15-kDa protein and characterized it as a selenoprotein of unknown function. In contrast to selenoproteins, low molecular mass [75Se]compounds accumulated during HIV infection and migrated as a diffuse band near the front of SDS/PAGE gels.     

Selenium intake as a modulator of responsiveness to oxidative stress

A deficiency in important components of the endogenous antioxidative defense system (AODS) against the production of reactive oxygen species, including free radicals, results in the accumulation of oxidative damage, inducing oxidative stress. A dietary deficiency in selenium (Se), an important part of AODS, can increase the sensitivity of a living system to oxidative stress. We investigated the effects of Se supplementation, in the form of Se-enriched yeast, on the AODS resistance of red blood cells (RBC) to experimentally induced oxidative stress. We analyzed the alterations in main components of the AODS, such as the amount of reduced (GSH) oxidized glutathione (GSSG), Se-dependent glutathione peroxidase (GSH-Px), Se content, catalase (CAT), and thiobarbituric acid reactive substances (TBARS), in RBC of male Wistar rats exposed to gamma rays and supplemented with Se-enriched yeast (SeY) in drinking water. The results suggested that the increased Se level generally exhibited a protective effect against whole body irradiation, reducing the expenditure of the AODS components in defense. These reductions differed depending on the time observed and the parameter investigated but, generally, SeY supplementation induced a faster restoration of the AODS after this kind of oxidative stress.     

Predictive models of carpal tunnel syndrome causation among VDT operators

Gpx2 mRNA, encoding a selenium-dependent glutathione peroxidase (GPX-GI), has been found to be highly expressed in the gastrointestinal tract (GI) mucosal epithelium. In this study, we show that GPX-GI is produced in the mucosal epithelium of the adult rat GI tract and that the activity levels are comparable to that from GPX-1. Post-mitochondrial supernatant GPX activity from the mucosal epithelium of the complete length of the small intestine was partially purified. A sample enriched for putative GPX-GI was fractionated by SDS-polyacrylamide gel electrophoresis. Polypeptides of 21 kDa and 22 kDa were digested with trypsin. After resolving the tryptic peptides by high pressure liquid chromatography (HPLC), the major peaks were analyzed for their amino acid sequence by Microflow-HPLC-Tandem Mass Spectrometry and automated Edman degradation sequencing. Both methods revealed that the 21-kDa sample contained rat GPX-GI determined by the sequence homology with the deduced mouse GPX-GI polypeptide sequence. Rat GPX-1 was also detected in the samples. AntiGPX-GI and antiGPX-1 antibodies were used to determine the distribution of the respective isoenzyme activities along the length of the intestine and with respect to the crypt to villus axis in rats. GPX-GI and GPX-1 activities were uniformly distributed in the middle and lower GI tract and with respect to the crypt to villus axis. GPX-GI activity accounted nearly the same percentage of the total GPX activity as GPX-1 in all of the these compartments. Studies on the distal ileum segment of wildtype and Gpx1 gene knockout mice showed that GPX-GI activity was also at parity with GPX-1 in the mucosal epithelium of this segment.     

Low-selenium diet, bone, and articular cartilage in rats

The pathophysiology of secondary osteoarthritis remains largely obscure. Our attention has been drawn to Kashin-Beck disease (KBD), which has been attributed to Se deficiency. To obtain information regarding the prevention, prediction of progression, and treatment of this condition, we performed histological and biochemical studies on bone and articular cartilage specimens obtained from rats fed a low-Se diet. A low-Se diet was prepared and fed to Wistar rats for 3-11 mo, after which the rats were killed under general anesthesia, and their articular cartilages were studied microscopically and electron microscopically. The bone mineral density (BMD) of the femur was determined by the microdensitometry method and ash weight. In addition, serum Se, Ca, P, Alk Phos, T3, T4, and urinary Se were measured. In the low-Se group, impaired weight gain was observed from the 5th mo, and head alopecia was found in 60% of the animals. Microscopically, no clear changes in the articular chondrocytes were apparent, whereas with the electron microscope, chondrocytes in the deep layer showed degeneration of nuclei and endoplasmic reticular ballooning. From the 5th mo, a decrease in BMD (ash weight) was noted. Serum Se concentrations, alkaline phosphatase activity, and urine Se concentrations were decreased in the Se-deficient rats, whereas serum Ca, P, T3, and T4 values did not differ from those of a control group. Also, a decrease in sulfotransferase activity, which is involved in transfer in the process of synthesis of glycosaminoglycan, which is a proteoglycan carbohydrate chain, was found.(ABSTRACT TRUNCATED AT 250 WORDS)     

A high glycemic index starch diet affects lipid storage-related enzymes in normal and to a lesser extent in diabetic rats

The of this study was to evaluate the chronic effects of a high (waxy corn) vs. a low (mung beans) glycemic index starch diet on the lipogenic enzymes, fatty acid synthase (FAS) and lipoprotein lipase (LPL). Normal and diabetic (streptozotocin-injected on d 2 of life) male Sprague-Dawley rats consumed a diet containing 575 g/kg carbohydrates either as waxy cornstarch (WCS) or as mung bean starch (MBS). After 3 wk, neither body weights nor relative epididymal fat pad weights differed. In diabetic rats, the WCS diet induced high basal plasma insulin levels. Plasma triglycerides were not significantly affected by diet in either normal or diabetic rats. Adipose tissue and liver LPL activities were not modified by the type of starch in the diet. In normal rats, FAS activity and gene expression in epididymal adipose tissue but not in liver were greater in rats consuming the WCS diet than in those consuming MBS. To evaluate the implication of insulin in this regulation, two genes regulated by insulin [GLUT4 and phosphoenolpyruvate carboxykinase (PEPCK)] were also studied. The high glycemic index WCS diet compared with the low glycemic index MBS diet resulted in lower hepatic PEPCK mRNA in both normal and diabetic rats. Normal, but not diabetic rats fed WCS had greater GLUT4 gene expression in adipocytes than did those fed MBS. We conclude that the total replacement of 575 g/kg low glycemic index starch by a high glycemic index starch for 3 wk caused the following in normal rats: 1) high FAS activity and mRNA in adipose tissue but not in liver and 2) high GLUT4 gene expression in adipose tissue. In both normal and diabetic rats this same diet resulted in lower hepatic PEPCK mRNA. Therefore, high glycemic index starch diet is implicated in stimulating FAS activity and lipogenesis and might have undesirable long-term metabolic effects.     

Lipid peroxidation in vivo during vitamin E and selenium deficiency in the rat as monitored by ethane evolution

Ethane evolution was monitored from vitamin E and selenium (Se)-deficient rats to determine if lipid peroxidation occurs in vivo when these rats develop fatal organ lesions. Weanling rats were fed a vitamin E and Se-deficient, or supplemented, diet for 40 to 90 days. Each was then prefasted for 4 hours and fasting was continued for 24 to 40 hours while ethane was collected. Approximately 50% of the doubly-deficient rats died as a result of fasting. Pathological signs included hematuria, lung hemorrhage, and liver necrosis. Ethane evolution increased exponentially 10 to 20 hours before death and then declined 2 hours before death. Rats that survived (at least 5 days after ethane collection) evolved 7.4+/-1.3 nmoles ethane/100 g body weight/24 hours compared to 100+/-6 for rats that died. Supplementation of the basal diet with vitamin E (200 IU/kg), Se (0.2 ppm, as Na2SeO3), or both, completely prevented mortality and reduced ethane evolution values to 0.4+/-0.2, 3.1+/-0.4, or 0.2+/-0.2, respectively. These experiments indicate that lipid peroxidation occurs in vivo as a result of vitamin E and Se deficiency, and the peroxidation process greatly accelerates during the terminal phase of the fatal disease.     

Dimensional changes related to ordering in an AuCu-3wt%Ga alloy at intraoral temperature

In this study, the overfed rat was employed as a model for examining the influence of obesity on the regulation of hepatic cytochromes P450 3A and 2C11 (CYP3A and CYP2C11, respectively). These proteins represent the predominant constitutive hepatic P450 enzymes of male rats. Sprague-Dawley rats were chronically fed a standard pelleted diet or an energy-dense diet which typically results in significant increases in body weight, serum triglyceride levels and liver lipid content. Obesity did not influence baseline levels of spectral cytochrome P450 content. Similar baseline activities of CYP3A (testosterone 6 beta-hydroxylation), comparative CYP3A protein levels (Western blot) and steady-state CYP3A mRNA (slot blot), were found in rats fed either diet. Likewise, obesity did not appear to influence CYP2C11 at the enzyme activity (testosterone 2 alpha-hydroxylation) or mRNA levels. Half of the animals in each group received 20 mg phenobarbital (intraperitoneal injection) per animal every 12 hours for three consecutive days. This resulted in similar phenobarbital plasma concentrations in both groups. Phenobarbital treatment increased the concentrations of total cytochrome P450 in both lean and obese rats to the same extent. CYP3A activity, protein and mRNA levels were induced to a similar magnitude in rats fed either diet. Furthermore, obesity did not influence CYP2C11 activity or mRNA levels following administration of phenobarbital. A lack of an effect of obesity and the altered lipid environment on the regulation of CYP3A and CYP2C11 is in contrast to other enzymes studied previously. It is apparent that the consequences of obesity on hepatic cytochrome P450 may be enzyme-specific.     

Comparison of three different methods for radiolabelling human activated T lymphocytes

The purpose of this study was to determine both the selenium (Se) level and glutathione peroxidase (GSH-Px) activity in plasma, erythrocytes and platelets from 51 healthy Japanese individuals. The Se levels (mean +/- SD) of plasma, erythrocytes and platelets were 117.4 +/- 15.7 micrograms/L, 0.954 +/- 0.159 microgram/g hemoglobin, and 4.93 +/- 1.52 ng/mg protein, respectively, and GSH-Px activity was 318 +/- 50 U/L, 18.0 +/- 5.0 U/g hemoglobin, and 0.142 +/- 0.035 U/mg protein, respectively. There was a negative correlation between age and the platelet Se level in men (r = -0.761, p < 0.001), and a positive correlation between the plasma and platelet GSH-Px activities in women (r = 0.663, p < 0.001).