A prior administration of heavy metals reduces thymus lymphocyte DNA lesions and lipid peroxidation in gamma-irradiated mice

In the present work we report that a prior injection of Pb, Cd or Zn salt solutions in SHK male mice decreases the effect followed $\gamma$-irradiation on thymus lymphocyte DNA structure and level of lipid peroxidation. It is assumed that the observed phenomenon is caused by activation of protective mechanisms of cells, expression of the genes of antioxidant proteins such as the metallothioneins, etc. Indeed the measurement of malondialdehyde (MDA) in blood plasma showed that the injection of metal salt solutions at median lethal doses a half hour before $\gamma$-irradiation (1 Gy) causes the decrease of the MDA contents at 48 h after irradiation on 100% (Zn), 70% (Cd) and 20% (Pb). However we found that combined exposure of the mice also results to significant decrease of the thymus lymphocytes total number of as compared to the irradiation without metals. The elimination of the cells with high level of DNA lesions and existence at least a subset of cells which would survive the current oxidative stress ($\gamma$-irradiation) possibly represents one path-way of the survival of individual organism facing stress. ln turn the observed decrease of the lesion levels may be reflection of the cell number change