Studies on ferrous ion-induced lipid peroxidation of rat liver mitochondria. I. Effect of inorganic phosphate.

Effect of inorganic phosphate on ferrous ionand ascorbate-induced lipid. peroxidations of isolated rat liver mitochondria was investigated. As a result it has been shown that phosphate accelerates the ferrous ion.induced lipid peroxidation; namely, phos. phate shortens the induction lag period of the lipid peroxidation reaction but the malondialdehyde after onset of its production is yielded at the same rate in various concentrations of phosphate. On the other hand, phosphate inhibits ascorbate.induced lipid peroxidation. There are stoichiometric interactions between the concentration of phos. phate and the induction period. Oxygen uptake by mitochondria was observed in the presence of both ferrous ion and phosphate at initial step of the reaction without being accompanied by malondialdehyde production, and afterwards there occurred malondialdehyde production with rapid rate of the oxygen uptake. Possible mechanisms and interactions among ferrous ion, ascorbate and phosphate were discussed. ∗PMID: 4281994 [PubMed indexed for MEDLINE] Copyright c ©OKAYAMA UNIVERSITY MEDICAL SCHOOL Acta Med. Okayama 28, 299-'-310 (1974) STUDIES ON FERROUS ION-INDUCED LIPID PEROXIDATION OF RAT LIVER MITOCHONDRIA. I. EFFECT OF INORGANIC PHOSPHATE Goki YAMAMOTO, Masatada TANABE, Hiroshi WAKABAYASHI, G6nosuke HASHIMOTO and Michio YAMAMOTO Department of Radiation Medicine, Okayama University Medical School, Okayama, Japan (Director: Prof. M. Yamamoto) Receivedfor publication, April 23, 1974 Abstract: Effect of inorganic phosphate on ferrous ionand ascorbate-induced lipid. peroxidations of isolated rat liver mitochondria was investigated. As a result it has been shown that phosphate accelerates the ferrous ion.induced lipid peroxidation; namely, phos. phate shortens the induction lag period of the lipid peroxidation reaction but the malondialdehyde after onset of its production is yielded at the same rate in various concentrations of phosphate. On the other hand, phosphate inhibits ascorbate.induced lipid peroxidation. There are stoichiometric interactions between the concentration of phos. phate and the induction period. Oxygen uptake by mitochondria was observed in the presence of both ferrous ion and phosphate at initial step of the reaction without being accompanied by malondialdehyde production, and afterwards there occurred malondialdehyde production with rapid rate of the oxygen uptake. Possible mechanisms and interactions among ferrous ion, ascorbate and phosphate were discussed. Effect of inorganic phosphate on ferrous ionand ascorbate-induced lipid. peroxidations of isolated rat liver mitochondria was investigated. As a result it has been shown that phosphate accelerates the ferrous ion.induced lipid peroxidation; namely, phos. phate shortens the induction lag period of the lipid peroxidation reaction but the malondialdehyde after onset of its production is yielded at the same rate in various concentrations of phosphate. On the other hand, phosphate inhibits ascorbate.induced lipid peroxidation. There are stoichiometric interactions between the concentration of phos. phate and the induction period. Oxygen uptake by mitochondria was observed in the presence of both ferrous ion and phosphate at initial step of the reaction without being accompanied by malondialdehyde production, and afterwards there occurred malondialdehyde production with rapid rate of the oxygen uptake. Possible mechanisms and interactions among ferrous ion, ascorbate and phosphate were discussed. The presence of unsaturated fatty acids in the phospholipid of mitochondrial membrane appeared to be essential for energy transfer reactions (1). It is of importance to consider the possibility that some intermediates of oxidative phosphorylation are associated with the polyunsaturated fatty acids which lead to lipid peroxide formation or accumulation under certain conditions (2). It has been reported that lipid peroxides may be formed during normal activity of electron transport chain in vitamine E-deficient rat liver mitochondria (3). Phosphate induces mitochondrial swelling which is dependent on electron transport and generation of high energy intermediates in the process of oxidative phosphorylation (4,5). It is of interest to know the interaction of phosphate with lipid peroxidation in mitochondria. Mitochondrial lipid peroxidation has been demonstrated correlatively with mitochondrial membrane alterations (swelling, lysis and disintegration) (2, 6, 7). Ferrous ion seems to be specific to the initiation of lipid peroxidation in mitochondria (8-11). However, the mechanism of mitochondrial lipid peroxidation