Studies on the lipid peroxidation in mitochondria of x-ray whole body irradiated rat liver Ⅰ. Change of Fe(++) -induced lipid peroxidation of mitochondria isolated from rat liver after irradiation

Lipid peroxidation of biomembrane is important in terms of the mechanism which are involved in the regulation and deterioration of their structure. To elucidate the behavior of lipid peroxidation in biomembrane after x-ray irradiation, the lipid peroxidation induced by Fe(++) in mitochondria after whole body irradiation was investigated, and the results are presented as follows. (1) Mitochondria were isolated from rat liver with the passage of day after 650 R irradiation, and the change of Fe(++) -induced lipid peroxidation was estimated by the TBA assay. Rates of the lipid peroxidation increased after irradiation and reached a maximum 3 days after irradiation, which was shown by shortening the lag of induction period and by the increase of TBA value per mg of protein. The increment of the activity was temporary and then the activity returned. (2) On the 3rd day after irradiation, the rat was more light in weight, and the wet weight of liver per body weight and the yield of mitochondria per tissue equivalent were increased transitorily in parallel with the change of the TBA value. (3) The shortening lag period and the high rate of TBA value depend on the dose of whole body irradiation. (4) The activity of oxidative phosphorylation of the mitochondria on the 3rd day after irradiation did not differ as compared with that of normal mitochondria. (5) These results suggest that the change of Fe(++) -induced lipid peroxidation of mitochondria after whole body irradiation is due to the irradiation. The factors in regulating the rate of lipid peroxidation were discussed