title: In vivo and in vitro variations of human erythrocyte glutathione peroxidase activity as result of cells ageing, selenium availability and peroxide activation.
abstract: 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 vivo 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 increase, and these variations are inversely related to the initial GSH-Px activity  in youngest cells. In vitro experiments with the addition of acetyl-phynyl-hydrazine strongly suggest that elevation of GSH-Px activity may be due to allosteric enzyme activation by activated oxygen.
mesh_terms: D000747:Anemia, Hypochromic / Q000201:enzymology; D001853:Bone Marrow / Q000201:enzymology; D004789:Enzyme Activation / Q000187:drug effects; D004905:Erythrocyte Aging; D004912:Erythrocytes / Q000201:enzymology*; D005979:Glutathione Peroxidase / Q000097:blood*; D006801:Humans; D066298:In Vitro Techniques; D010544:Peroxidases / Q000097:blood*; D010545:Peroxides / Q000378:metabolism; D012643:Selenium / Q000494:pharmacology
chemical_list: D010545:Peroxides; D010544:Peroxidases; D005979:Glutathione Peroxidase; D012643:Selenium