Inhibition of DNA repair by cadmium and lead in sheep lymphocytes: protective interaction of magnesium

The effects of magnesium on the genotoxicity of cadmium chloride and lead acetate were investigated. The DNA repair as the genotoxicity test was determined in cultured sheep lymphocytes treated with the heavy metals in combination with UV-induced DNA damage. Excision repair was performed by incorporation of [³H]-thymidine into DNA of lymphocytes synchronised with hydroxyurea in G₁/S phase. The results show that DNA repair was strongly affected by cadmium (Il) but only slightly in cells treated with lead, indicating rather mitogenic properties. Repair inhibition made by cadmium was restored after treatment of lymphocyte cultures with 0.4 mM. of magnesium chloride for six hours. In conclusion, genotoxicity of Cd or Pb to lymphocytic DNA was markedly decreased by the presence of Mg in culture media.