Adaptive response to ionizing radiation-induced chromosome aberrations in rabbit lymphocytes: Effect of pre-exposure to zinc, and copper salts

Various stress conditions including exposure to low-dose radiation and low concentrations of chemical mutagens can induce an adaptive response to subsequent radiation-induced chromosome damage. In this study, the effect of pretreatment of rabbit lymphocytes with zinc or copper salts on radiation-induced chromosome damage was investigated, Pretreatment of rabbit peripheral lymphocytes with Zn (50 mu M in vitro or 100 mu mol/g body weight in vivo) resulted in resistance to gamma radiation (2.0 Gy)-induced chromosome aberrations such as dicentrics plus centric rings and cells with chromosome aberrations. On the other hand, pretreatment with Cu (50 mu M in vitro) did not show any protective effect on radiation-induced chromosome damage in rabbit lymphocytes. However, the concentration of metallothionein increased in activated lymphocytes 24 h after in vitro pretreatment with both Zn and Cu. In addition, gamma-radiation-induced calf thymus DNA damage could be prevented directly by the addition of Zn-metallothionein in the cell free system. These results suggest that the induction of zinc-metallothionein synthesis may act as one of the defensive mechanisms to the induction of cytogenetic adaptive response to ionizing radiation while copper-metallothionein did not show any radioprotective effect.