[Plasmid DNA breakage caused by reaction of intracellular redox compound with potassium dichromate]

To study plasmid DNA breakage induced by hexavalent chromium (Cr(VI +)) compound in vitro.

DNA breakage was observed using plasmid relaxation method.

pUC 118 plasmid DNA single strand breakage can not be caused by either ascorbic acid (1 mmol/L), or glutathione (5 mmol/L), or hydrogen peroxide (H(2)O(2), 17 mmol/L) or potassium dichromate (K(2)Cr(2)O(7), 0.5 mmol/L) alone. But, if DNA was incubated warmly with K(2)Cr(2)O(7) and intracellular redox compound, pUC118 plasmid DNA single strand breakage could be induced by K(2)Cr(2)O(7), ascorbic acid, or glutathione, or products of peroxidation reaction. K(2)Cr(2)O(7) (0.5 mmol/L) and H(2)O(2) (17 mmol/L) also could cause some double-strand breakage in plasmid.

It suggests that ascorbic acid, glutathione and H(2)O(2) can play an important role in carcinogenicity of K(2)Cr(2)O(7).