STUDIES BY ELECTRON-PARAMAGNETIC-RESONANCE OF THE IMPORTANCE OF IRON IN THE HYDROXYL SCAVENGING PROPERTIES OF ASCORBIC-ACID IN PLASMA - EFFECTS OF IRON CHELATORS

Ascorbic acid is considered to be the most important antioxidant of pl asma. Its oxidation leads to the ascorbyl free radical (AFR), detected by electron paramagnetic resonance (EPR) spectroscopy. The purpose of this study was to investigate by EPR the interaction of plasma AFR le vels in different situations of oxidative stress. Our results showed t hat plasma AFR remains constant after rat feeding with vitamin C (5 mg or 50 mg per 100 g body weight). We also demonstrated that: (1) the a scorbyl free radical (AFR) level was increased after direct addition o f iron Fe3+/EDTA to plasma, the optimal level was reached after additi on of 8 mu M Fe3+/EDTA (1:2); (2) this AFR production was associated w ith the formation of hydroxyl radicals. Iron chelators (deferrioxamine . a synthetic iron chelator and apotransferrine. a biological iron che lator) added just before the Fe3+/EDTA complex inhibited the increase of AFR signal induced by this complex. The scavenging effect of plasma was significantly correlated with the AFR production. Therefore, AFR, which is naturally present in plasma, could be used as an index of ox idative stress in which free radicals or adverse iron mobilisation are implicated. (C) Elsevier, Paris.