Superoxide dismutase and glutathione peroxidase abnormalities in erythrocytes and lymphoid cells in Down syndrome.

After validating a superoxide dismutase (SOD) assay, this enzyme was measured together with a large series of cell age sensitive marker enzymes, in the erythrocytes of 24 persons with the 24 persons without Down syndrome. In addition to the expected elevation of SOD-1, significant elevations of erythrocyte glutathione peroxidase (GSHPxase) and phosphofructokinase activities were found in Down syndrome. None of these changes could be accounted for by a decreased mean red cell age. The elevation of GSHPxase was also found in lymphoid cells but does not represent a gene dose effect at this locus. Rather, the elevation of GSHPxase in Down syndrome may represent an adaptive metabolic response to the increased hydrogen peroxide produced by the triplicated SOD-1 gene dose in trisomy 21. Since tissue GSHPxase activity can be manipulated via the enzyme's obligatory selenium co-factor, our data suggest the need to establish blood and tissue levels of selenium in Down syndrome and to correlate selenium, GSHPxase and phenotypic dysfunction in this disorder.