Yamashita Y, Sumi N, Arimoto S, Hayatsu H
Graduate School of Natural Science and Technology, Okayama University, Japan.
Mutat Res. 1995 Dec;348(4):163-8. doi: 10.1016/0165-7992(95)90004-7.
N-Nitrosodialkylamines are promutagens and proclastogens, requiring metabolic activation for their actions. Previously, we showed that direct-acting bacterial mutagens can be formed from N-nitrosodialkylamines on exposure to near-UV. We have now found that N-nitrosodialkylamines with near-UV irradiation are clastogenic to Chinese hamster lung cells. When the cells in culture were irradiated with near-UV for 3 h in the presence of N-nitrosodimethylamine (NDMA), N-nitrosodiethylamine (NDEA), N-nitrosopyrrolidine (NPYR), N-nitrosopiperidine (NPIP) or N-nitrosomorpholine (NMOR), and then further incubated for a total period of 24 h with the N-nitrosodialkylamines, chromosome aberrations were induced. Neither the N-nitrosodialkylamine nor near-UV alone were clastogenic. Severe clastogenicity (> 50% of cells examined showing aberrations) was observed for 0.5 mM NDEA, NPYR and NPIP. The order of the clastogenic activity was NDEA, NPYR > NPIP, NDMA > NMOR. This order differed from that of bacterial mutagenicity previously reported for these N-nitrosodialkylamines plus near-UV, in which NMOR gave the strongest activity. The chromosome aberrations induced by the NPYR and NDEA plus near-UV in CHL-cells were inhibited by superoxide dismutase, glutathione and L-cysteine. Dimethylsulfoxide or D-mannitol, scavengers of hydroxy radical, and L-histidine, a scavenger of single oxygen, were ineffective. These results suggest that superoxide formed by a synergistic action of an N-nitrosodialkylamine and near-UV is the cause of the chromosome aberrations observed, an assumption consistent with the known ability of superoxide to cleave DNA.
N-亚硝基二烷基胺是前诱变剂和断裂剂，其作用需要代谢激活。此前，我们发现N-亚硝基二烷基胺在近紫外光照射下可形成直接作用的细菌诱变剂。我们现在发现，经近紫外光照射的N-亚硝基二烷基胺对中国仓鼠肺细胞具有断裂作用。当培养的细胞在存在N-亚硝基二甲胺（NDMA）、N-亚硝基二乙胺（NDEA）、N-亚硝基吡咯烷（NPYR）、N-亚硝基哌啶（NPIP）或N-亚硝基吗啉（NMOR）的情况下用近紫外光照射3小时，然后再与N-亚硝基二烷基胺一起孵育总共24小时，会诱导染色体畸变。单独的N-亚硝基二烷基胺或近紫外光都没有断裂作用。对于0.5 mM的NDEA、NPYR和NPIP，观察到严重的断裂作用（>50%的检测细胞显示畸变）。断裂活性的顺序为NDEA、NPYR>NPIP、NDMA>NMOR。这个顺序与之前报道的这些N-亚硝基二烷基胺加近紫外光的细菌诱变性顺序不同，在之前的顺序中NMOR活性最强。超氧化物歧化酶、谷胱甘肽和L-半胱氨酸可抑制NPYR和NDEA加近紫外光在CHL细胞中诱导的染色体畸变。羟基自由基清除剂二甲亚砜或D-甘露醇以及单线态氧清除剂L-组氨酸无效。这些结果表明，N-亚硝基二烷基胺和近紫外光协同作用形成的超氧化物是观察到的染色体畸变的原因，这一假设与超氧化物已知的切割DNA的能力一致。
