Studies on ferrous ion-induced lipid peroxidation Part Ⅱ Analysis of the induction period (lag) of ferrous ion-induced lipid peroxidation

The author measured simultaneously Fe(Ⅱ)-induced peroxidation of lipid extracted from rat liver mitochondria by the TBA method and the concentration of Fe(Ⅱ) added to the medium quantitatively using Nitoroso-PSAP reagent. 1) An induction period (lag) at the early phase of the reaction of Fe(Ⅱ)-induced lipid peroxidation was observed as well as in mitochondria. 2) After most of the Fe(Ⅱ) concentration had decreased, the TBA-value, after lagtime, increased sharply. 3) Phosphate added to the medium shortened the lag-time. The lag-time in the presence of phosphate varied with the concentration and pH. However, in each case, there was a correlation between the decrement of Fe(Ⅱ) concentration and the length of lag time as described above. 4) By adding EDTA for various reaction times, Fe was chelated immediately, then the TBA value did not increase. 5) The results suggest: iron interacted with the chain reaction of lipid peroxidation, mainly as Fe(Ⅱ) and/or partially Fe(Ⅲ); Fe(Ⅱ) maintains the lag as a inhibitory action to the resolution into malondialdehyde(MDA) from lipid peroxide; Fe(Ⅲ) was required for the formation of MDA. 6) Using these results, the author discussed the mechanisms of Fe(Ⅱ)-induced lipid peroxidation.