Crocidolite-induced lipid peroxidation in rat lung microsomes. I. Role of different ions

Lipid peroxidation is increased by ferrous or ferric ions in rat lung microsomes both from rats pretreated with 3-methylcholanthrene and from untreated controls. This increase was dependent on the concentration of these ions in the reaction mixture. Crocidolite alone increased peroxidation in microsomal fractions. However, addition of ferric or ferrous ions with the crocidolite did not give a greater increase in the amount of peroxidation in microsomes. Chelation with EDTA of iron, whether originally present as free ions in the solution or attached to crocidolite, prevented lipid peroxidation. NADPH alone, when added to the microsomal fractions, did not produce any significant effect. However, when added concomitantly with crocidolite fibers, NADPH reduced the effect of crocidolite on lipid peroxidation. Magnesium, manganese, and calcium ions did not produce any significant effect on lipid peroxidation in the presence or absence of crocidolite. A reduced pH enhanced the rate of lipid peroxidation in line with increased solubility of iron salts at these pH values. All the above observations, taken together, lead to the conclusion that it is the iron in the crocidolite that is responsible for the latter's ability to enhance lipid peroxidation.