Effects of in vivo exposure to low doses of different radiator nuclides on DNA repair capability

Objective: To elucidate the effects and mechanism of in vivo exposure to low doses of different radiator nuclides on DNA repair capability. Methods: The DNA excision repair capacity, as measured by UV-induced unscheduled DNA synthesis (UDS), of splenic lymphocytes and germ cells from inbred BALB/c male mice was observed after injection of different dose of 235UO2F2 or 147Pm(NO3)3 into tail vein. Results: UV-induced UDS of the splenic lymphocytes was significantly increased (P<0.05 or 0.01) when the mice were exposed to 235UO2F2 at doses of 0.1-20 μg/kg body weight or 147Pm at doses of 37-185 Bq/g body weight, and UV-induced UDS of the germ cells was also increased at above doses of 147Pm (P<0.05 or 0.01). While the UV-induced UDS of these cells was decreased at doses of 3 700 kBq/g body weight of 147Pm (P<0.05 or 0.01). Non-UV-induced UDS showed a significant increase on the 12th day after 235UO2F2 injection(P < 0.05 or 0.01). The values of UV-induced UDS in PHA activated but non-proliferating (hydroxyurea treated) lymphocytes were lower than those of lymphocytes unexposed to PHA at the same doses of 235UO2F2(P < 0.05 or 0.01). Conclusion: Low doses of internally deposited 235UO2F2 and 147Pm have a continuous damage effect on DNA of the murine somatic and germ cells so that a significant stimulative effect on DNA excision repair of the cells is induced. But higher doses of 147Pm irradiation have a significant inhibitory effect on DNA repair of those cells.The stimulative effect occurs only in a limited range of dose. In PHA stimulated but non-proliferating lymphocytes, the DNA repair synthesis is significantly inhibited after UV-irradiation