Selenium, zinc and copper in Down's syndrome (trisomy 21): blood levels and relations with glutathione peroxidase and superoxide dismutase.

Increased superoxide dismutase and glutathione peroxidase activities have been reported in erythrocytes of subjects with Down's syndrome. Since these enzymes contain specific trace-elements as essential components, we have determined copper, zinc and selenium levels in plasma and erythrocytes of 29 trisomy 21 patients compared with 32 age-matched controls and examined the relations with the enzymes' activities. In plasma, mean zinc and copper levels were normal, but selenium was found to be significantly decreased (p less than 0.001). In red cells, the increase of activity of the selenoenzyme glutathione peroxidase (p less than 0.001) was not accompanied by an increase of erythrocyte selenium, but a significant correlation was found between these two values (r = 0.67, p less than 0.001). Zinc and copper levels in red cells were significantly higher than normal (p less than 0.001) and this increase could be partly explained by the increased activity of the copper and zinc containing enzyme superoxide dismutase (p less than 0.001). Low plasma selenium and the strong relation between erythrocyte selenium and glutathione peroxidase activity we found in Down's syndrome should stimulate interest in a more detailed investigation of selenium status and metabolism of these patients.