重铬酸钾和氧化还原物质反应致质粒DNA断链

Plasmid DNA Breakage Caused by Reaction of Intracellular Redox Compound with Potassium Dichromate

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。

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 2O 2, 17 mmol/L) or potassium dichromate (K 2Cr 2O 7, 0.5 mmol/L) alone. But, if DNA was incubated warmly with K 2Cr 2O 7 and intracellular redox compound, pUC118 plasmid DNA single strand breakage could be induced by K 2Cr 2O 7, ascorbic acid, or glutathione, or products of peroxidation reaction. K 2Cr 2O 7 (0.5 mmol/L) and H 2O 2 (17 mmol/L) also could cause some double strand breakage in plasmid. Conclusion It suggests that ascorbic acid, glutathione and H 2O 2 can play an important role in carcinogenicity of K 2Cr 2O 7.