Mohn G R, Kerklaan P R, ten Bokkum-Coenradi W P, ten Hulscher T E
Mutat Res. 1983 Aug;113(5):403-15. doi: 10.1016/0165-1161(83)90230-3.
The feasibility of performing tests for repairable DNA damage in animal assay procedures was investigated by using repair-proficient and repair-deficient derivatives of E. coli K12 strain 343/113, including mutations in the uvrB, recA, polA and dam genes. To avoid variations in the relative recovery of viable cells from different samples, the strains were further marked with auxotrophic growth requirements, so that mixtures could be treated and the survival of each strain determined individually on media containing the corresponding growth factors. Spot tests were performed with the various strains to re-assess the necessity of using a combination of repair deficiencies, when genotoxic agents of differing mode of action are to be detected. Liquid suspension tests on mixtures of the different strains, furthermore, confirmed that the survival of the individual strains can be determined separately on selective media after treatment with methyl methanesulfonate (MMS) and methyl nitrosourea (MNU). These tests were also used to demonstrate that dimethyl nitrosamine (DMNA) is activated by Aroclor-1254-induced rat-liver S9 fractions to genotoxic products, as measured by the low survival of a recA derivative compared with the repair-proficient wild-type strain. Intrasanguineous host-mediated assays using the present derivatives of E. coli K12/343/113 showed that the various strains, injected simultaneously into mice, could be recovered in amounts sufficient for the individual determination of the relative survival in liver, spleen, lungs, kidneys, pancreas and the blood stream of the host animals. Using a mixture of the repair-proficient parent and the recA derivative inoculated into mice that were subsequently treated with MMS, NMU or DMNA, we found that these chemicals induce a larger decrease in survival in the recA strain as compared with the wild-type in cells recovered from the liver and the spleen. The order of genotoxic potency so determined was DMNA greater than MNU greater than MMS; this is similar to the ranking of the carcinogenicity of these compounds in rodents and probably also reflects the various degrees of DNA alkylation in cells of the livers of the treated animals. The general usefulness of the host-mediated differential DNA repair assay for detecting genotoxic factors in various organs of animals remains to be assessed by using chemical mutagens of different modes of action.
利用大肠杆菌K12菌株343/113的修复 proficient和修复 deficient衍生物，包括uvrB、recA、polA和dam基因的突变，研究了在动物试验程序中进行可修复DNA损伤测试的可行性。为避免不同样品中活细胞相对回收率的差异，这些菌株进一步标记了营养缺陷型生长需求，以便处理混合物，并在含有相应生长因子的培养基上单独测定每个菌株的存活率。对各种菌株进行斑点试验，以重新评估在检测不同作用方式的遗传毒性剂时使用修复缺陷组合的必要性。此外，对不同菌株混合物进行的液体悬浮试验证实，在用甲磺酸甲酯（MMS）和甲基亚硝基脲（MNU）处理后，可以在选择性培养基上分别测定各个菌株的存活率。这些试验还用于证明，通过与修复 proficient的野生型菌株相比recA衍生物的低存活率来衡量，二甲基亚硝胺（DMNA）被Aroclor - 1254诱导的大鼠肝脏S9组分激活为遗传毒性产物。使用大肠杆菌K12/343/113的当前衍生物进行的体内宿主介导试验表明，可以同时注射到小鼠体内的各种菌株，能够以足够的数量回收，用于单独测定宿主动物肝脏、脾脏、肺、肾、胰腺和血流中的相对存活率。使用接种到小鼠体内的修复 proficient亲本和recA衍生物的混合物，随后用MMS、NMU或DMNA处理，我们发现与从肝脏和脾脏回收的细胞中的野生型相比，这些化学物质在recA菌株中诱导的存活率下降更大。如此确定的遗传毒性效力顺序为DMNA大于MNU大于MMS；这与这些化合物在啮齿动物中的致癌性排名相似，可能也反映了处理动物肝脏细胞中DNA烷基化的不同程度。宿主介导的差异DNA修复试验在检测动物各个器官中的遗传毒性因子方面的一般实用性，仍有待通过使用不同作用方式的化学诱变剂来评估。
