INCREASED SUSCEPTIBILITY OF MICROCYTIC RED-BLOOD-CELLS TO IN-VITRO OXIDATIVE STRESS

Oxidative damage to erythrocytes in thalassaemia has been related to g eneration of free radicals by an excess of denaturated alpha- or beta globin chains, intracellular iron overload and low concentration of no rmal haemoglobin (HGB). Two good indicators of such oxidative damage a re the high red blood cell (RBC) malonyldialdehyde (MDA) production de tected following exogenous oxidant stress and the decrease of pyrimidi ne 5-nucleotidase (P5N), the most sensitive enzyme to SH-group damage in vivo. Conflicting data, however, have so far accumulated in the lit erature concerning differences in oxidative damage between the differe nt forms of thalassaemia and iron deficiency anaemia (IDA). In the pre sent study, oxidative susceptibility, as defined by the production of MDA in vitro and antioxidant capacity, as measured by the activity of RBC glutathione peroxidase (GPx), superoxide dismutase (SOD) and by re duced glutathione (GSH), have been studied in microcytic RBCs from pat ients with beta-thalassaemia trait, Spanish (delta beta)degrees-thalas saemia heterozygotes (delta beta-thalassaemia trait) and iron deficien cy anaemia (IDA). The results are consistent with the existence of sig nificant differences in the severity and pattern of oxidative stress s usceptibility between beta-thalassaemia trait (increased MDA productio n and higher SOD and GPx activities) and the other two forms of microc ytosis (delta beta thalassaemia trait and IDA). Furthermore, the findi ng of normal P5'N activity in delta beta thalassaemia trait, gives fur ther support to the less intense peroxidative environment of RBCs in t his form of thalassaemia when compared to beta-thalassaemia trait, cha racterized by acquired RBC P5'N deficiency due to oxidative damage.