[Effect of low doses of external and internal ionizing radiation on proteinases of cells in the rat cerebral cortex of rats].

Single external gamma-irradiation in a dose of 0.5-2 Gy as well as the long-term (30 days) internal irradiation caused by the everyday influx of Cs-137 and Sr-85 isotopes to the organism have been studied for their effect on the activity and properties of histone-specific proteinase from the nuclei of the rat brain cortex cells. It is found out that external irradiation induces a dose-dependent increase of the activity during the first 24 hours after irradiation followed by its decrease 7-30 days later. Internal irradiation induces a decrease of the enzyme activity at the 30th day as well. Certain specificity of the studied indices depending on the type of irradiation has been also observed.