Direct ESR measurement of mutagenic slow releasing long-lived radicals in irradiated mammalian cells with adequate dose for radiayion biology

Abstract

We newly found novel slow-releasing long-lived radicals (SRLLRs) in 4 Gy gamma-ray irradiated cultured SHE cells by ESR spectroscopy without any spin-trapping agents. Levels of SRLLRs increased 18 and 36 % with an increase at intervals of 1 and 5 h AFTER irradiation, respectively, and were kept in the same until 12 h at least. Post-treatment of Vitamin C for 2 h suppressed the increase in the levels of SRLLRs. Addition of myxothiazol, as an inhibitor of electron transportation in mitochondria, suppressed the increase in the level of SRLLRs in irradiated cells, and direct addition of hydrogen peroxide to the cells increased the levels of them. These results indicate that SRLLRs are likely to be produced by hydrogen peroxide from dysfunctional mitochondria. Because SRLLRs have a long lifetime over 12 h and reduced by ascorbate, they might be responsible of late effects of radiation including point mutation.