重铬酸钾和氧化还原物质反应致质粒DNA断链

目的　在体外研究六价铬化合物诱导质粒ＤＮＡ 链断裂的作用。方法　采用质粒松弛法。结果　重铬酸钾（０ ．５ ｍｍｏｌ／Ｌ） 、抗坏血酸（１ ｍｍｏｌ／Ｌ） 、谷胱甘肽（５ ｍｍｏｌ／Ｌ） 或过氧化氢（１７ｍｍｏｌ／Ｌ） 单独作用都不能诱导明显的ＤＮＡ 单链断裂。然而,将重铬酸钾和具有氧化还原功能的物质与ＤＮＡ 共同温浴,发现重铬酸钾和抗坏血酸、谷胱甘肽或过氧化氢反应后可明显诱导质粒ＤＮＡ 单链断裂。重铬酸钾和过氧化氢（１７ ｍｍｏｌ／Ｌ） 还诱导质粒ＤＮＡ 双链断裂。结论　抗坏血酸、谷胱甘肽和过氧化氢可能在重铬酸钾的致癌过程中起重要作用。

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

OBJECTIVE: To study plasmid DNA breakage induced by hexavalent chromium (Cr(VI +)) compound in vitro. METHODS: DNA breakage was observed using plasmid relaxation method. RESULTS: 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. CONCLUSION: 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).