氧自由基对大肠癌细胞rRNA基因活性和DNA含量的影响

目的探讨氧自由基对癌细胞核酸和基因活性的影响。方法采用计算机图像分析法测定叔丁基脂氢过氧化物（ｔｂｏｏＨ）对直肠腺癌ＨＲ８３４８细胞系间期细胞核及中期染色体上核仁组织区嗜银蛋白（ＡｇＮＯＲｓ）的作用，同时测定ＤＮＡ含量和细胞毒效应。结果１０－６ｍｏｌ／Ｌ的ｔｂｏｏＨ能使体外生长的大肠癌细胞出现细胞毒作用；ＡｇＮＯＲｓ颗粒在ｔｂｏｏＨ作用早期以聚集型为主，颗粒面积增大，而晚期颗粒分散，数量明显减少。早期ＡｇＮＯＲｓ颗粒增大并非是染色体上ｒＲＮＡ基因活性位点的增多，而是与间期细胞核内ＡｇＮＯＲｓ的聚集状态有关；晚期间期细胞内ＡｇＮＯＲｓ减少则是由ｔｂｏｏＨ引起染色体上ｒＲＮＡ基因位点减少所致。ｔｂｏｏＨ还可引起癌细胞ＤＮＡ含量减少。结论细胞基因活性或ＤＮＡ改变是自由基介导细胞损伤的重要机制。

EFFECTS OF OXY-RADICAL ON rRNA GENE ACTIVITY AND DNA CONTENTS OF HR 8348 IN VITRO

PURPOSE To investigate the relationship between free radicals and cytotoxicity and to study the effects of oxy-radical on nucleic acid and gene activity.METHODS The changes of silvered nucleolar organizer regions (AgNORs) induced by tbooH in interphase and metaphase of HR 8348 (a rectal cancer cell line)were observed by means of a computer image analysis. DNA content and cytotoxicity were also measured.RESULTS 10-6 mol/L tbooH could result in cytoxicity of cancer cells. Through rRNA gene activity analysis, it was shown that AgNORs clusters were mainly seen in the early stage of free radical action,later the AgNORs became smaller and dispersed, the mean number of AgNORs per nuclei decreased remarkably. Compared to the results of rRNA gene activity in chromosomes, it was shown that the decreased number of AgNORs in chromosomes were responsible for interphase AgNORs decrease in late stage of tbooH treatment. In this stage,the contents of DNA were also decreased.CONCLUSIONS It is suggested that the changes of gene activity and DNA content in cancer cells induced by free radicals may be an important mechanism for cytoxicity.