Park J W, Ames B N
Department of Biochemistry, University of California, Berkeley 94720.
Proc Natl Acad Sci U S A. 1988 Oct;85(20):7467-70. doi: 10.1073/pnas.85.20.7467.
The 7-methylguanine adduct in the DNA of rat liver is determined as an indicator of exposure to exogenous and endogenous methylating agents. A method for the analysis of 7-methylguanine adducts has been developed by combining the selectivity of separation of reversed-phase HPLC with the specificity and high sensitivity of electrochemical detection. The sensitivity of the method is about 10,000-fold that of optical methods and is sufficient to determine the endogenous background of DNA methylation. DNA from the liver of normal young rats (6 months old) contains 7-methylguanine at a level of 1 residue per 31,000 bases in mitochondrial DNA and 1 residue per 105,000 bases in nuclear DNA. These levels increase about 2.5-fold in old rats (24 months old). We attribute this strikingly high level of adducts to endogenous methylation, which could contribute to aging and cancer.
测定大鼠肝脏DNA中的7-甲基鸟嘌呤加合物，作为接触外源性和内源性甲基化剂的一个指标。通过将反相高效液相色谱分离的选择性与电化学检测的特异性和高灵敏度相结合，开发出一种分析7-甲基鸟嘌呤加合物的方法。该方法的灵敏度约为光学方法的10000倍，足以测定DNA甲基化的内源性背景。正常年轻大鼠（6个月大）肝脏中的DNA，在线粒体DNA中每31000个碱基含有1个7-甲基鸟嘌呤残基，在核DNA中每105000个碱基含有1个。在老年大鼠（24个月大）中，这些水平增加约2.5倍。我们将这种加合物的极高水平归因于内源性甲基化，它可能与衰老和癌症有关。
