In Vivo and in Vitro Variations of Human Erythrocyte Glutathione Peroxidase Activity as Result of Cells Ageing, Selenium Availability and Peroxide Activation

Abstract

Erythrocyte glutathione peroxidase (GSH-Px) defects were previously described. A number of non-genetic factors were demonstrated which may influence the GSH-Px activity in human erythrocytes. Se administration in vivo was followed in 4 subjects by elevation in erythrocyte GSH-Px activity ranging from 30-1400%. Se operates mainly in the bone marrow erythroblasts by facilitating the synthesis of active GSH-Px molecules. Experiments in vitro demonstrate that, in the youngest erythrocytes, Se can raise the enzyme activity, but by a different mechanism. The reticulocyte GSH-Px activity appears to depend on Se availability and may vary over a wide range. In some normal and iron deficient subjects, the GSH-Px activity in the youngest erythrocyte fraction was equal or lower than that previously found in whole erythrocytes of patients affected by hemolytic anemia. During erythrocyte life, GSH-Px activity may diminish or increase, and these variations are inversely related to the initial GSH-Px activity in the youngest cells. In vitro experiments with the addition of acetyl-phenyl-hydrazine strongly suggest that elevation of GSH-Px activity may be due to allosteric enzyme activation by activated oxygen.