A comparative study on the effect of MNU on human lymphocyte cultures in vitro evaluated by O⁶-mdG formation, micronuclei and sister chromatid exchanges induction

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• 作者：Stephanou ; G. ; Vlastos ; D. ; Vlachodimitropoulos ; D. ; Demopoulos ; N.A.
• 关键词：Immuno-slot-blot ; Sister chromatic exchanges ; Micronuclei ; O⁶-Methyldeoxyguanosine
• 刊名：Cancer Letters
• 出版年：1996
• 期刊代码：44_03043835
• 类别：med
• 出版时间：December 3, 1996
• 卷：109
• 期：1-2
• 页码：109-114
• 文件大小：447 K

摘要

N-Nitroso-compounds are a large group of chemicals present in a number of environmental sources and many of them are mutagens as well as carcinogens in experimental animals. Among the known N-nitroso-compounds, N-nitroso-N-methylurea (MNU) is a strong mutagen. In this study an effort has been made to compare the ability of MNU to methylate the O⁶-guanosine site in DNA and to induce micronuclei and sister chromatic exchanges in human lymphocyte cultures in vitro. To quantitate O⁶-methyldeoxyguanosine (O⁶-mdG) a highly sensitive immunoassay, immuno-slot-blot (ISB), has been used. For the evaluation of micro nuclei (MN) the cytokinesis block micronucleus method has been used. Different concentrations (75, 100, 125 μg/ml) were tested. At the highest concentration tested for the MN induction, 125 μg/ml, the occurrence of binucleates and micro nuclei is higher than twice in relation to control and a reduction in NDI is also observed. The same concentrations were used for the estimation of sister chromatid exchanges (SCEs) induction. The mean number of SCEs at 125 μg/ml is almost three times that of the control level. The concentrations tested for the quantitation of O⁶-mdG were 200, 300 and 400 μg/ml and this was done because for the test system we used and for the given experimental conditions the first indication of O⁶-mdG formation was at 200 μg/ml. Our results show that methylation of O⁶-guanosine increases with concentration and at 400 μg/ml the concentration of O⁶-mdG is 5.83 fmol/μg DNA, while at the control level it is 2.40 fmol/μg DNA. Since O⁶-mdG formation is observed in higher concentrations than those of MN and SCE induction it would be interpreted that O⁶-mdG levels are not correlated with the studied cytogenetic effects although one has to take into consideration the total promutagenic lesions in DNA, induced by MNU, as well as AGT repair activity.