Cancer Research Campaign Section of Genome Damage and Repair, Paterson Institute for Cancer Research, Christie Hospital NHS Trust, Manchester, M20 9BX, UK.
Biomarkers. 1999;4(4):254-62. doi: 10.1080/135475099230787.
Outbred 7-week old male Wistar rats were exposed for 21 days to N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) via the drinking water and N7-methyl deoxyguanosine 3'-monophosphate (N7-MedGp) levels in DNA from the pyloric mucosa (target tissue) and white blood cells (wbc: non-target tissue) were determined by (32)P-postlabelling. Exposure to MNNG resulted in the non-linear, dose-related formation of N7-medGp in both tissues. Adduct levels in the pyloric mucosa were determined to be 1058, 5.4 and 1.1 μmole N7-medGp mole(-1) deoxyguanosine 3'-monophosphate (dGp) after exposure to 4.1, 0.62 and 0.006 mg MNNG kg(-1) day(-1) respectively whereas adduct levels in the wbc DNA were lower at 5.2, 0.52 and 0.68 μmoles N7-medGp mole(-1) dGp after exposure to 4.1, 0.62 and 0.062 mg MNNG kg(-1) day(-1) respectively. In addition, the persistence of N7-medGp was investigated. Loss of adduct occurred rapidly, with a decrease of 87 and 97% respectively in target tissue and wbc DNA by 48 h after cessation of 4.1 mg MNNG kg(-1) day(-1) exposure; 14 days post-MNNG treatment, however, N7-medGp was still detectable (0.46 μmole N7-medGp mole(-1) dGp) in pyloric mucosal DNA. The quantitation of N7-medGp after exposure to low doses of carcinogen, i.e. 0.006 mg MNNG kg(-1) day(-1), approaching environmentally relevant levels has not been previously reported, and indicates that the (32)P-postlabelling assay developed here possesses sufficient sensitivity to quantitate N7- medGp in human DNA arising from environmental exposure to methylating agents.
经饮用水摄入 N-甲基-N'-硝基-N-亚硝胍（MNNG），21 天后，对杂交 7 周龄雄性 Wistar 大鼠进行染毒，采用（32）P-后标记法测定胃幽门黏膜（靶组织）和白细胞（wbc：非靶组织）中的 N7-甲基脱氧鸟苷 3'-单磷酸（N7-MedGp）水平。MNNG 暴露导致两种组织中 N7-medGp 的形成呈非线性、剂量相关性。经 4.1、0.62 和 0.006mgMNNGkg-1day-1 染毒后，胃幽门黏膜中的加合物水平分别为 1058、5.4 和 1.1μmoleN7-medGp 摩尔-1 脱氧鸟苷 3'-单磷酸（dGp），而白细胞 DNA 中的加合物水平分别为 5.2、0.52 和 0.68μmolesN7-medGp 摩尔-1 dGp。此外，还研究了 N7-medGp 的持久性。加合物的损失迅速发生，在停止 4.1mgMNNGkg-1day-1 染毒 48 小时后，靶组织和 wbcDNA 中的加合物分别减少 87%和 97%；然而，MNNG 处理 14 天后，胃幽门黏膜 DNA 中仍可检测到 N7-medGp（0.46μMoleN7-medGp 摩尔-1 dGp）。以前没有报道过在接触低剂量致癌物（即 0.006mgMNNGkg-1day-1）后定量测定 N7-medGp 的情况，这表明此处开发的（32）P-后标记法具有足够的灵敏度来定量测定人类 DNA 中因环境暴露于甲基化剂而产生的 N7-medGp。
