Okochi E, Kurahashi A, Mochizuki M
Kyoritsu College of Pharmacy, Tokyo, Japan.
Mutat Res. 1997 Jan 3;373(1):99-105. doi: 10.1016/s0027-5107(96)00194-7.
A chemical model system for cytochrome P450, a porphyrin and an oxidant, was used in Ames assay as a substitute for S9 mix. In the presence of tetrakis(pentafluorophenyl)porphyrinatoiron(III) chloride [Fe(F5P)Cl] and tert-butyl hydroperoxide (t-BuOOH), mutagenicity of N-nitrosodibutylamine (NDB) in Salmonella typhimurium TA1535 was detected. The mutagenicity depended on the pre-incubation period, and also on the concentration of an oxidant and of bacteria. In the chemical model system, pH affected the mutagenicity of NDB, which suggested that as observed in an enzymatic activating system, the mutagenicity was due to the labile alkylating species which was derived from NDB activated in the chemical activation system and was sensitive to pH. Under the optimum conditions; a higher concentration of an oxidant, a higher concentration of bacterial culture, and a weakly acidic medium, mutagenicity of N-nitrosodipropylamine in S. typhimurium TA1535 was also detected. Besides N-nitrosodialkylamines, 2-aminofluorene (2-AF) and benzo[a]pyrene (BaP) were also used as mutagens. Mutagenicity of 2-AF and BaP in S. typhimurium TA1538 were both detected in the same system as used in detecting the mutagenicity of N-nitrosodialkylamines. Ames test using a metalloporphyrin/oxidant model system makes it possible to detect mutagenicity derived from both base pair substitution mutagens and frameshift mutagens without using enzymatic activating system. These results demonstrate that the assay with the chemical model system is useful in detecting unstable unknown active mutagens or investigating the mechanisms of the metabolic pathway of mutagens or carcinogens in a protein-free medium.
一种用于细胞色素P450的化学模型系统，即卟啉和氧化剂，在艾姆斯试验中被用作S9混合物的替代品。在四（五氟苯基）卟啉铁（III）氯化物[Fe(F5P)Cl]和叔丁基过氧化氢（t-BuOOH）存在的情况下，检测了N-亚硝基二丁胺（NDB）在鼠伤寒沙门氏菌TA1535中的致突变性。致突变性取决于预孵育时间，还取决于氧化剂和细菌的浓度。在化学模型系统中，pH影响NDB的致突变性，这表明正如在酶促活化系统中所观察到的，致突变性是由于不稳定的烷基化物种，该物种源自化学活化系统中活化的NDB，并且对pH敏感。在最佳条件下；较高浓度的氧化剂、较高浓度的细菌培养物和弱酸性介质，还检测到了N-亚硝基二丙胺在鼠伤寒沙门氏菌TA1535中的致突变性。除了N-亚硝基二烷基胺外，2-氨基芴（2-AF）和苯并[a]芘（BaP）也被用作诱变剂。2-AF和BaP在鼠伤寒沙门氏菌TA1538中的致突变性在与检测N-亚硝基二烷基胺致突变性相同的系统中均被检测到。使用金属卟啉/氧化剂模型系统进行艾姆斯试验使得无需使用酶促活化系统就能够检测来自碱基对取代诱变剂和移码诱变剂的致突变性。这些结果表明，使用化学模型系统进行的检测对于检测不稳定的未知活性诱变剂或研究无蛋白质培养基中诱变剂或致癌物代谢途径的机制是有用的。
