Cadmium-induced dna single-strand scissions and their repair in cultured chinese hamster cells

Abstract

DNA lesions induced by cadmium chloride (CdCl 2) were characterized using the technique of alkaline or neutral elution for cell-DNA in cultured V79 cells. A marked increase in elution of the DNA was observed on elution of the proteinase-K-digested cell lysates with alkaline eluting solution (pH 12.2) after treatment with 5.10 −5M CdCl 2 for 2 h. In contrast, no increase in elution of the DNA was observed when the same cell lysates were eluted with an eluting solution of pH 9.6. These findings indicate that the DNA lesions induced by cadmium were DNA single-strand but not double-strand scissions. The DNA single-strand scissions by cadmium were partly rejoined after 4 h of repair incubation. However, the DNA lesions were not rejoined up to the control level in the technique of alkaline elution, even after 20 h of repair incubation. On the other hand, an apparent increase in elution of the DNA was observed by combined treatment with cadmium and inhibitors of repair DNA synthesis, hydroxyurea (HU) and 1-β-D-arabinofuranosylcytosine (ara-C), for 4 h when compared to elution of the DNA from the cells treated with cadmium alone or HU and ara-C. These results indicate that cadmium-induced DNA single-strand scissions accumulated as a result of inhibition of repair DNA replication by HU and ara-C. Thus, it is concluded that cadmium-induced DNA single-strand scissions were repairable and their repair might be dependent upon the excision repair mechanism.