In vivo and in vitro variations of human erythrocyte glutathione peroxidase activity as result of cells ageing, selenium availability and peroxide activation.

Cases showing erythrocyte glutathione peroxidase (GSH‐Px) defects have been previously described. Our experiments demonstrate that a number of non genetic factors may influence the GSH‐PX activity in human erythrocytes. Selenium administration in vivo was followed in four subjects by elevation in erythrocyte GSH‐Px activity ranging from 30% to 1400%. Selenium 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, selenium can raise the enzyme activity, but by a different mechanism. The reticulocyte GSH‐Px activity appears to depend on selenium 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 haemolytic anaemia. During erythrocyte life, GSH‐Px activity may either diminish or increas...