The effect of irradiation on sub-cellular particles- Destruction of sulphydryl groups

SummaryThiol groups of rat-liver nuclei, mitochondria, lysosomes, and microsomes are destroyed by irradiation in vitro with electron doses of 5–50 kilorads. Significant destruction of thiol content occurs in all sub-cellular fractions immediately after a dose of 5 kilorads, the percentage of -SH groups destroyed being 9·5 per cent in the nuclei, 23 per cent in the lysosomes, 9·1 per cent in the mitochondria and 2·8 per cent in the microsomes. The percentage of thiol groups destroyed increased with radiation dose in all fractions. Incubation in air or oxygen at 4°c, 20°c or 37°c after irradiation causes further destruction of sulphydryl groups, but this does not occur after incubation in nitrogen.It is suggested that the destruction of -SH groups is a result of oxidation by free radicals produced in the aqueous phase and is not a result of oxidation by lipid peroxides.