Related Experiment Videos
Selenium repletion and glutathione peroxidase--differential effects on plasma and red blood cell enzyme activity
Insights
Children with chronic gastrointestinal disease on long-term intravenous nutrition showed low selenium and glutathione peroxidase. Selenium supplementation rapidly normalized plasma activity and gradually increased red blood cell activity in new cells.
Area of Science:
- Biochemistry
- Pediatrics
- Nutrition Science
Background:
- Chronic gastrointestinal disease can impair nutrient absorption.
- Intravenous hyperalimentation (IVH) is a life-sustaining therapy for severe GI disorders.
- Nutrient deficiencies, including trace elements like selenium, can occur with long-term IVH.
Observation:
- Three pediatric patients on intravenous hyperalimentation presented with low plasma and red blood cell glutathione peroxidase activity.
- Two patients exhibited marked serum selenium deficiency, with enzyme activities at 4-24% of normal.
- Red blood cell glutathione peroxidase activity showed a delayed increase after selenium repletion, appearing in newly synthesized cells.
Findings:
- Supplementation with sodium selenite (240 micrograms Se/d) normalized plasma glutathione peroxidase activity within 4-5 weeks.
- Red blood cell glutathione peroxidase activity remained low for 4-6 weeks before gradually increasing over 3-4 months.
- Analysis of red blood cells by density gradient revealed that selenium repletion led to increased enzyme activity in younger cells first.
Implications:
- Selenium is crucial for glutathione peroxidase activity, impacting both plasma and red blood cells.
- Intravenous hyperalimentation regimens require careful monitoring for selenium status.
- Understanding the kinetics of red blood cell enzyme synthesis is important for managing nutritional deficiencies.
Abstract:
We studied three children with chronic gastrointestinal disease who had been on intravenous hyperalimentation for periods of time ranging from 4 to 23 months. Each child was found to have low plasma and red blood cell glutathione peroxidase activity. This was associated, in the two children tested, with a marked deficiency of serum selenium. Their plasma glutathione peroxidase levels ranged between 4 and 24% of normal and their red blood cell levels ranged between 4 and 14% of normal. The intravenous alimentation was then supplemented with sodium selenite (240 micrograms Se/d). Within 4-5 weeks, the plasma glutathione peroxidase activity returned to normal. Red cell glutathione peroxidase activity remained essentially unchanged for 4-6 weeks, after which it increased over the following 3-4 months. Red cells were separated by density on a continuous Percoll-diatrizoate gradient. In normal individuals, the specific activity of glutathione peroxidase did not differ across the gradient despite a 2.5-fold difference in the specific activity of pyruvate kinase. When studied initially, glutathione peroxidase activity from the deficient patients did not change across the gradient. As the red cell enzyme activity increased with selenium repletion, the highest specific activity was initially found at the top of the gradient (youngest cells). After 3-4 months of supplementation, the specific activity became equal across the gradient. Thus, with selenium repletion, there is a rapid increase in plasma glutathione peroxidase activity, a 4-6 week lag prior to an increase in red cell enzyme activity, and the increase in red cell activity is due to newly synthesized red cells made in the presence of selenium.