[Low doses of radiation decrease the level of spontaneous and gamma-induced chromosomal mutagenesis in bone marrow cells of mice in vivo].

Low doses of ionizing radiation are known to induce adaptive response (AR), which is characterized in most cases by temporary nature, though the possibility of long-term persistence of AR is not ruled out. In this investigation we studied the effect of low doses of gamma-radiation on both high-dose radiation-induced and spontaneous level of cytogenetic damage throughout the life of mice. SHK male mice 2 months old were used. Priming doses of 0.1 and 0.2 Gy (0.125 Gy/min, gamma-radiation from 60Co) were used. A challenging dose of 1.5 Gy (1 Gy/min) was used in the experiments using a routine AR experimental design. The frequency of micronucleated polychromatic erythrocytes in bone marrow cells of primed, primed and challenged, and control groups was assessed at various times of animal life span. It was shown that: a) single low-dose gamma-irradiation induces a cytogenetic AR which can be revealed at 1, 3, 6, 9, 12 months after priming; b) single low-dose gamma-irradiation decreases the cytogenetic damage to a level below the spontaneous rate at the end of lifetime (20 months) of animals; c) ability to induce adaptive response does not depend on the age of animals at the moment of priming irradiation. In conclusion, the mechanisms underlying AR not only protect from chromosome damage induced by high-dose irradiation but also may play a role in spontaneous mutagenesis during aging of animals.