Effect of prolonged supplementation with daily supplements of selenomethionine and sodium selenite on glutathione peroxidase activity in blood of New Zealand residents.

Glutathione peroxidase (EC 1.11.1.9, GSH-Px) activities and selenium (Se) concentrations in blood of 12 New Zealand residents were followed during prolonged supplementation with physiological doses (100 microgram Se) of sodium selenite (selenite-Se) or selenomethionine (Semet-Se). GSH-Px activities increased in all subjects but at 17 wk the mean increase was not significantly greater for Semet-Se (6.2 +/- SD 3.2 units/g Hb) than for selenite-Se (3.7 +/- 1.8 units/g Hb). After dosing ceased, GSH-Px activities for most subjects returned to predosing values in 17 to 40 wk, but in some subjects activities remained high. Increases in Se concentrations in whole blood, erythrocytes, and plasma were greater after Semet-Se than after selenite-se. Se concentrations tended to plateau after selenite-Se while after Semet-Se they continued to rise as long as dosing continued. Enzyme activity of one of four subjects supplemented daily with 500 microgram selenite-Se was unchanged, despite a great increase in plasma Se. Blood Se and GSH-Px of 23 New Zealand residents who ingest regular large doses (0.5 to 3 mg Se) mainly of selenite-Se showed that those who dosed weekly had greater values than the less frequent dosers. Three subjects showed extremely high values. It is suggested that each individual might have an optimal level of GSH-Px activity, so that the level reached is a balance between Se intake and other factors, including possible stressor effect of selenite.

Effect of daily supplements of selenium on patients with muscular complaints in Otago and Canterbury.

The alleged beneficial effect of selenium (Se) on fibromuscular rheumatism in residents of low soil-Se areas of New Zealand has been explored. Three dosing trials, two of them double blind trials, using physiological daily supplements (100 micrograms Se) of sodium selenite or selenomethionine and a placebo have been carried out. Blood Se and glutathione peroxidase (EC 1.11.1.9; GSHPX) activities were monitored and clinical assessment of the efficacy of the treatment was made during the trials. Blood Se and GSHPX activities rose in all patients who received Se whereas those in control groups remained more or less constant throughout the study. Clinical assessment of muscular symptoms showed that approximately half of the patients in both trial groups and placebo groups responded to treatment. Thus we have been unable to give conclusive evidence of a response to Se supplementation for relief of muscular complaints.

Relation between erythrocyte selenium concentrations and glutathione peroxidase (EC 1.11.1.9) activities of New Zealand residents and visitors to New Zealand.

1. Erythrocyte, plasma and whole blood selenium concentrations and glutathione peroxidase (EC 1.11.1.9; GSHPx) activities were measured (1) in 104 healthy New Zealand residents living in Otago, a low-soil-Se area (2) in sixty-four surgical patients, including nineteen patients on total parenteral nutrition and twenty-three cancer patients (3) in fifty-two 'overseas subjects' (twenty-five visitors to Otago from outside New Zealand and twenty-seven Otago residents on return from overseas travel). 2. Blood Se concentrations reflected dietary Se intake; means for Otago patients, healthy subjects and overseas subjects were different 0.043, 0.059, 0.136 micrograms Se/ml blood respectively) and mean for overseas residents was greater than for New Zealand overseas travellers. 3. Erythrocyte Se concentration was always greater than plasma Se, and plasma Se was a smaller proportion of erythrocyte Se for patients compared with the controls. 4. GSHPx activities were different in the three groups, and varied directly with erythrocyte Se until a plateau was reached at approximately 0.14 micrograms Se/ml erythrocytes. 5. Overseas subjects showed no relationship between erythrocyte Se and GSHPx activity. This agrees with some overseas studies and the significance of this finding is discussed. 6. Plasma Se concentration remained the most sensitivie index of short-term changes in Se status, and erythrocyte Se and GSHPx activities for long-term changes in New Zealand subjects. Use of these measurements for overseas subjects with higher blood levels is discussed.

Blood selenium and glutathione peroxidase activity in normal subjects and in surgical patients with and without cancer in New Zealand.

This study was carried out in Otago, South Island, where most arable land has a low soil selenium content (less than 0.5 microgram/g) and where selenium (Se) responsive diseases in livestock are common. Se concentration in whole blood, erythrocytes and plasma, and activity of glutathione peroxidase (EC 1.11.1.9) were measured in blood from 104 healthy Otago residents, 80 patients with cancer and 66 noncancer surgical patients. The older residents over 60 years had lower blood Se levels (0.047 +/- 0.010 microgram Se/ml blood) than the young and middle-aged (0.060 +/- 0.012 microgram Se/ml). Blood Se levels of cancer patients were no lower than those of elderly subjects and patients without cancer, and were less than half comparable United States values. Blood Se levels were decreasing in two cancer patients, and the lowest values (less than 0.03 microgram Se/ml blood) were obtained for five cancer patients, and two noncancer patients after a long period of inanition; these were similar to values for patients on parenteral nutrition with negligible intakes. Lower blood Se levels were associated with lower serum albumin and enzyme activities. It is suggested that low Se status of cancer patients was more likely a consequence of their illness than the cause of the cancer.

Selenium concentration and glutathione peroxidase activity in blood of New Zealand infants and children.

The blood selenium (Se) concentrations of New Zealand children were lower than those reported for children living in other countries. This low blood Se was primarily determined by the low dietary intake of the children which, in turn, reflects the low Se content of New Zealand soils. Blood Se also varied geographically, with age, and with differences in quantities and types of food eaten. Children with phenylketonuria and maple syrup urine disease on synthetic diets had low Se intakes and blood Se concentrations compared with children on normal diets, and blood Se was seen to decrease with the length of time on these diets. A strong correlation (r = 0.62, P less than 0.001) was found between the blood Se levels and glutathione peroxidase activities for 107 children. Glutathione peroxidase activities of the children were lower than activities observed in New Zealand adults, refelecting their lower blood Se concentrations.

On supplementing the selenium intake of New Zealanders. 2. Prolonged metabolic experiments with daily supplements of selenomethionine, selenite and fish.

1. The daily intake of selenium by three subjects was supplemented with 100 microgram Se as selenomethionine (Semet-Se) or sodium selenite (selenite-Se)/d for 10-11 weeks, or with 65 microgram Se as in mackerel (Scomber japonicus) (fish-Se)/d for 4 weeks. 2. Urinary and faecal excretion of Se was measured and also Se concentration in whole blood, plasma and erythrocytes. Measurements on blood were made at intervals after supplementation had ceased. 3. Selenite-Se was not as well absorbed (0.46 of the intake) during the first 4 weeks as Semet-Se (0.75 of the intake) and fish Se (0.66 of the intake). 4. Blood Se increased steadily with Semet-Se, from 0.08 to 0.18 microgram Se/ml, but more slowly with selenite-Se, reaching a plateau in 7-8 weeks at 0.11 microgram Se/ml. Plasma Se increased more rapidly with Semet-Se than with selenite-Se, so that initially with Semet-Se plasma Se was greater than erythrocyte Se. 5. Daily urinary excretion increased with all forms of supplement, with initially a greater proportion of absorbed selenite-Se being excreted than Semet-Se or fish-Se. A close relationship was found between plasma Se and 24 h urinary excretion. The findings suggested that there was a rapid initial excretion of presumably unbound Se then a slower excretion of residual unbound, loosely bound or bound Se. 6. Total retentions of 3.5 mg selenite-Se and 4.5 mg Semet-Se were large when compared with an estimate of body content of 6 mg Se, derived in another paper (Stewart, Griffiths, Thomson & Robinson, 1978). Retention of Semet-Se and fish-Se appeared to be reflected in blood Se, whereas for selenite-Se, blood Se reflected retention for only a short period after which Se appeared to be retained without altering the blood Se. This suggested that Semet-Se and selenite-Se were metabolized differently. 7. A double blind-dosing trail with 100 microgram Semet-Se was carried out for 12 weeks on twenty-four patients with muscular complaints in Tapanui, a low-Se-soil area. Blood Se increased in the experimental group (from 0.067 to 0.143 microgrm Se/ml); clinical findings were not conclusive and will be presented elsewhere. 8. Bood Se was measured in New Zealand residents before travelling to Europe or to North America. On return their blood Se was increased, and depending upon the period of time spent outside New Zealand some values reached concentrations found in visitors and new settlers to New Zealand. 9. The results from these studies and the earlier studies of single and multiple dosing have been used to look at the various criteria in use for assessing Se status of subjects. It is suggested that plasma Se be used in preference to 24 h urinary excretion, and in addition to whole blood Se and glutathione peroxidase (EC 1.11.1.9) activity.

Selenium concentrations and glutathione peroxidase activities in whole blood of New Zealand residents.

1. A relationship was found between selenium concentrations and glutathione peroxidase (EC 1.11.1.9) activities in whole blood of 264 New Zealand residents (r 0-71, P less than 0-001). 2. New Zealand residents returning from visits overseas of 7 months to 3 years had elevated blood Se, but normal GSH-Px activities, whereas for some new settlers in New Zealand both Se and GSH-Px activities were high.