Kompleksnost metabolizma slobodnih radikala u humanim eritrocitima
Complexity of free radical metabolism in human erythrocytes
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The auto-oxidation of oxyhaemoglobin to methaemoglobin generating superoxide anion radical (O2 .-) represents the main source of free radicals in the erythrocytes. Hydrogen peroxide is produced by O2 .- dismutation or originates from the circulation. Human erythrocytes are also exposed to the prooxidative actions of nitric oxide (NO) from circulation. Free radicals that may induce reactions with direct dangerous consequences to erythrocytes are also preceded by the reaction of O2 .- and NO producing per oxynitrite. In physiological settings, erythrocytes show a self-sustaining activity of antioxidative defense (AD) enzymes, such as: superoxide dismutase (SOD, EC 1.11.16), catalase (CAT, EC 188.8.131.52), glutathione peroxidase (GSHPx, EC 184.108.40.206) and glutathione reductase (GR, EC 220.127.116.11), as well as low molecular weight antioxidants: glutathione and vitamins E and C. Their coordinate actions protect the erythrocyte's biomacromolecules from free radical-mediated damage. Since there is no de novo synthesis of AD enzymes in mature erythrocytes, their defense capacity is limited. Free radicals influence antioxidative enzymes capacities and relative share of particular components in the whole anti oxidative system. Therefore, by measuring changes in the activity of individual AD components, as well as their inter relations by statistical canonical discriminate methods, valuable data about the complexity, overall relations and coordinated actions in the AD system in erythrocytes and its relevance for systemic effects can be acquired.