RESUMEN
In recent years, it has been hypothesized that an increase in oxidative stress in patients with Down syndrome account for the appearance of different diseases such as atherosclerosis, accelerated cell aging, cellular mutagenicity and neurological disorders that often occur in these patients. The antioxidant defense system enzymes have been shown to be altered due to increased gene dosage on chromosome 21 and overproducetion of superoxide dismutase. The purpose of this study was to investigate the activity of glutathione peroxidase enzyme [GPX] and the level of selenium [Se] as indicators of antioxidative metabolism in Down syndrome patients. The study was conducted on forty patients with Down syndrome. They were 21 males and19 females. Their ages ranged between 1 year and 11 years [mean 3.95 +/- 2.5 years]. Another group was randomly chosen as a control group, it included 10 normal infants and children, 5 males and 5 females. Their ages ranged between 1 year and 11 years [mean 3.95 +/- 4.47 years]. All cases and controls were subjected to plasma glutathione peroxidase enzyme assay and plasma selenium level determination. There was a significant increase in GPX activity in Down syndrome patients compared to the control group. There was no statistical significant difference between cases and controls as regards selenium level. In Down syndrome group, there was no significant difference in GPX and selenium levels between males and females and between different age groups. There was a significant negative correlation between GPX activity and Se level in Down syndrome patients. Down syndrome patients have increased activity of glutathione peroxidase enzyme and although they have normal plasma Se level, there is a significant negative correlation between selenium level and GPX activity. This finding suggests that the selenium requirement of the enzyme is not met and there is a relative selenium deficiency