Oxidation of ferrous iron during peroxidation of lipid substrates.
Oxidation of Fe2+ in solution was dependent upon medium composition and the presence of lipid. The complete oxidation of Fe2+ in 0.9% saline was markedly accelerated in the presence of phosphate or EDTA and the ferrous oxidation product formed was readily recoverable as Fe2+ by ascorbate reduction. In contrast, in the presence of either brain synaptosomal membranes, phospholipid liposomes, fatty acid micelles or H2O2, less than 50% of the Fe2+ oxidized during an incubation could be recovered as Fe2+ via reduction with ascorbate. In the presence of unsaturated lipid, oxidation of Fe2+ was associated with peroxidation of lipid, as assessed by the uptake of O2 and formation of thiobarbituric acid-reactive products during incubations. Although relatively little Fe2+ oxidation or lipid peroxidation occurred in saline with synaptosomes or linoleic acid micelles during an incubation with Fe2+ alone, significant Fe2+ oxidation and lipid peroxidation occurred in incubations containing a 1:1 ratio of Fe2+ and Fe3+. Extensive Fe2+ oxidation and lipid peroxidation also occurred with Fe2+ alone in saline incubations with either linolenic or arachidonic acid acid micelles or liposomes prepared from dilinoleoylphosphatidylcholine. While a 1:1 ratio of Fe2+ and Fe3+ enhanced thiobarbituric acid-reactive product formation in incubations containing linolenic or arachidonic micelles, it reduced the rate of O2 consumption as compared with Fe2+ alone. The results demonstrate that oxidation of Fe2+ in incubations containing lipid substrates is linked to and accelerated by peroxidation of those substrates. Furthermore, the results suggest that oxidation of Fe2+ in the presence of lipid or H2O2 creates forms of iron which differ from those formed during simple Fe2+ autoxidation.
D000818:Animals; D001205:Ascorbic Acid / Q000494:pharmacology; D001921:Brain / Q000378:metabolism; D004492:Edetic Acid / Q000494:pharmacology; D005290:Ferric Compounds / Q000378:metabolism; D005296:Ferrous Compounds / Q000378:metabolism*; D006861:Hydrogen Peroxide / Q000494:pharmacology; D008054:Lipid Peroxides / Q000378:metabolism*; D010084:Oxidation-Reduction; D010101:Oxygen Consumption / Q000187:drug effects; D010710:Phosphates / Q000494:pharmacology; D051381:Rats; D013574:Synaptosomes / Q000378:metabolism
D005290:Ferric Compounds; D005296:Ferrous Compounds; D008054:Lipid Peroxides; D010710:Phosphates; D004492:Edetic Acid; D006861:Hydrogen Peroxide; D001205:Ascorbic Acid