Stimulation of Fe(2+)-induced lipid peroxidation in phosphatidylcholine liposomes by aluminium ions at physiological pH.

The effects of aluminium ions on Fe(2+)-induced lipid peroxidation in egg yolk phosphatidylcholine liposomes were examined under various conditions. The degree of Fe(2+)-induced lipid peroxidation of the liposomes was dependent on pH of the reaction mixture: pH 5.0 > pH 7.4. However, Fe2+ did not induce lipid peroxidation in the liposomes at pH 9.0. The addition of AlCl3 to the liposomal suspension resulted in a marked stimulation of Fe(2+)-induced liposomal peroxidation at pH 7.4, depending on the concentration of AlCl3. On the other hand, Fe3+, Cu2+, Pb2+, Cd2+ and Cr6+ did not induce lipid peroxidation in the liposomes at pH 7.4 regardless of the presence and absence of AlCl3. Fe3+ enhanced Fe(2+)-induced liposomal peroxidation at pH 7.4 but is unrelated to the stimulatory effect of AlCl3. In the absence of AlCl3, Fe(2+)-induced liposomal peroxidation was observed after a lag phase of about 15 min. The lag phase of the reaction was shortened by the addition of AlCl3 in a dose-dependent fashion. The shortening of the lag phase was also observed by the decrease of Fe2+ concentration or by the co-presence of Fe3+ in the reaction mixture. In addition, it was found that AlCl3 stimulates Fe2+ disappearance and Fe3+ formation. The addition of AlCl3 to the liposomal suspension at pH 7.4 resulted in a marked increase of the turbidity of the suspension. On the other hand, the turbidity of the liposomal suspension at pH 5.0 did not change by the addition of AlCl3.(ABSTRACT TRUNCATED AT 250 WORDS)