Lipid Peroxides (TBA reactive substances)and Fatty Acid Compositions in Mouse Serum with Whole-body Irradiation and in Tumor-bearing Mouse Serum with Local Irradiation

Effects of irradiation on lipid peroxides of mouse serum, Ehrlich solid tumor-bearing mouse serum, which tomor cells were transplanted to the leg, and its tumor tissue were studied by a thiobarbituric acid (TBA) color reaction in the acetic acid condition with (Fe-TBA value) or without (TBA value) ferrous ammonium sulfate. TBA reactive substances were caluculated into the amount of malondialdehyde. Besides, fatty acid and lipid compositions were analyzed as a substrates. Irradiated samples were isolated at 3 days after irradiations. The TBA value of normal mouse serum was expressed 17nmoles/ml of serum, and Fe-TBA value gave 2.4-fold of the TBA value. Although an increase TBA value was not observed by whole-body irradiation, a significant increase of Fe-TBA value was measured, indicating 2.5-fold at 10Gy exposure compared with the normal Fe-TBA value, and 5.5-fold with the TBA value. The TBA value of tumor-bearing mouse serum was 14nmoles/ml as a low rate to that of normal serum, but the Fe-TBA value gave same magnification of that of normal one. The TBA value of tumor-bearing mouse serum was not changed by the local irradiation to the tumor region of leg, but the Fe-TBA value was increased 2.8 and 4.4 times at 10Gy and 20Gy exposures, respectively, comparing with the non-irradiated one, and 7.7 and 10.5 times with the TBA value, respectively. The TBA value of solid tumor homogenate exhibited 1.16nmoles/mg of protein, and the Fe-TBA value, pointed out 5 times as much as the TBA value. Both values slightly increased by the irradiation. These facts suggest that a shift of TBA value of serum hard to get, but Fe-TBA value of serum distinctly increases by the irradiation. The fatty acid composition of mouse serum lipids showed an increment of relative percentages of linoleic and arachidonic acids by the whole-body irradiation. The relative percentage of fatty acid compositon of lipids from solid tumor-bearing mouse serum was similar tendency to that of normal one, and the local exposure to the tumor part was not affected the each percentage. The percentage of high unsaturated fatty acid of tumor lipids similar to that of serum lipids, and a decrease of the percentage of arachidonic acid was accounted by the irradiation. In relative percentages of lipid compositions, the percentage of choleste rolester of serum lipids increased by the whole-body irradiation, and that of phospholipid fraction was not changed. In the case of tumor-bearing mouse serum lipids, an increment of the percentage of cholesterolester was obtained as compared with that of normal serum lipids, and this percentage decreased by the local irradiation to tumor part with an increment of the percentage of phospholipid. The percentage of phospholipid in tumor lipids had decreased by the irradiation. The facts suggest that a cause of the increased Fe-TBA value of tumor-bearing mouse serum by the irradiation to tumor is due to the release of peroxidizable phospholipid into serum from the damaged menbranes of tumor cells at large doses to exposure.