PROTECTIVE EFFECT OF MAGNESIUM ON DNA STRAND BREAKS INDUCED BY NICKELOR CADMIUM

Magnesium, an essential metal that is important in the normal function ing of DNA, has been shown to interact with some of the toxic heavy me tals in respect to biochemical and molecular mechanisms and in alterin g the tumorigenic process. This study examined the influence of magnes ium in combination with nickel and cadmium in respect to damage of the DNA molecule. The purpose of this study was to evaluate the influence of magnesium on the amelioration of the toxic metals nickel and cadmi um in respect to sustaining DNA damage. Two types of lymphocytes were used, i.e., primary Fischer 344 rat splenocytes and AHH-1 TK+/-, a hum an B-lymphoblastoid cell line that has been spontaneously transformed. These cells were grown in either a magnesium-free or magnesium-supple mented RPMI 1640 medium that was specifically formulated for this stud y. A 2 x 2 factorial design was employed with magnesium and either nic kel or cadmium serving as the two factors. The experimental groups wer e as follows: +Mg+Ni, +Mg-Ni, -Mg+Ni, -Mg-Ni, with cadmium alternating for the nickel in the subsequent studies. The nickel or cadmium was a dded at a concentration of 50 mumol/L. The presence of double-stranded DNA was determined in each of the respective treatment groups with th e two types of cell lines. Based on the results of this study, nickel is not directly toxic to DNA, whereas cadmium produces damage directly on the DNA molecule. The magnesium has little or no direct influence on the occurrence of DNA damage from nickel since the toxicity of nick el appears to be manifested in areas other than the DNA molecule, such as ia the heterochromatin. The presence of cadmium in the treatment g roup resulted in DNA damage, which in turn was reduced significantly b y the presence of magnesium.