Rosser P F, Ramachandran P, Sangaiah R, Austin R N, Gold A, Ball L M
Department of Environmental Sciences and Engineering, School of Public Health, University of North Carolina at Chapel Hill 27599-7400, USA.
Mutat Res. 1996 Aug 12;369(3-4):209-20. doi: 10.1016/s0165-1218(96)90026-9.
The genotoxic environmental contaminant 1-nitropyrene is metabolised in mammalian systems by pathways more complex than the straightforward nitroreduction which accounts for most of its biological activity in bacteria. In order to evaluate the role of O-acetyltransferase (OAT) activity in generation of genotoxic intermediates from 1-nitropyrene, the mutagenicity of the major primary oxidised metabolites of 1-nitropyrene was characterised in the Ames Salmonella typhimurium plate incorporation assay with strain TA98, and with variants of TA98 deficient (TA98/1,8-DNP6) or enhanced (YG1024) in O-acetyltransferase. 1-Nitropyren-3-ol was more mutagenic in the absence than in the presence of S9, while 1-nitropyren-4-ol, 1-nitropyren-6-ol and 1-nitropyren-8-ol required S9 for maximum expression of mutagenicity. 1-Nitropyren-4-ol (176 rev/nmol without S9, 467 rev/nmol with S9 in TA98) and 1-nitropyren-6-ol (13 rev/nmol without S9, 266 rev/nmol with S9 in TA98) were overall the most potent nitropyrenol isomers assayed. 1-Acetamidopyren-8-ol and 1-acetamidopyrene 4,5-quinone were only minimally active. 1-Acetamidopyren-3-ol exhibited direct-acting mutagenicity. 1-Acetamidopyren-6-ol, previously shown to be a major contributor to mutagenicity in the urines of rats dosed with 1-nitropyrene (Ball et al., 1984b), was confirmed as a potent (359 rev/nmol) S9-dependent mutagen. Both the direct-acting and the S9-dependent mutagenicity of all the compounds studied was enhanced in the OAT-overproducing strain and much diminished (though not always entirely lost) in the OAT-deficient strain, showing that OAT amplifies expression of the genotoxicity of these compounds. 1-Acetamidopyren-6-ol required both S9 and OAT activity in order to exhibit any mutagenicity; this finding strongly implicates N-hydroxylation followed by O-esterification, as opposed to further S9-catalyzed ring oxidation, as a major route of activation for urinary metabolites of 1-nitropyrene.
基因毒性环境污染物1-硝基芘在哺乳动物系统中的代谢途径比在细菌中占其大部分生物活性的直接硝基还原更为复杂。为了评估O-乙酰转移酶（OAT）活性在1-硝基芘产生基因毒性中间体过程中的作用，在鼠伤寒沙门氏菌TA98菌株以及O-乙酰转移酶缺陷型（TA98/1,8-DNP6）或增强型（YG1024）的TA98变体的艾姆斯平板掺入试验中，对1-硝基芘主要的初级氧化代谢产物的致突变性进行了表征。1-硝基芘-3-醇在无S9时比有S9时更具致突变性，而1-硝基芘-4-醇、1-硝基芘-6-醇和1-硝基芘-8-醇需要S9才能使致突变性最大程度表达。1-硝基芘-4-醇（在TA98中，无S9时为176回复突变数/纳摩尔，有S9时为467回复突变数/纳摩尔）和1-硝基芘-6-醇（在TA98中，无S9时为13回复突变数/纳摩尔，有S9时为266回复突变数/纳摩尔）总体上是所检测的最具活性的硝基芘醇异构体。1-乙酰氨基芘-8-醇和1-乙酰氨基芘-4,5-醌活性极低。1-乙酰氨基芘-3-醇表现出直接作用的致突变性。1-乙酰氨基芘-6-醇，先前已证明是给1-硝基芘染毒的大鼠尿液中致突变性的主要贡献者（Ball等人，1984b），被确认为一种强效的（359回复突变数/纳摩尔）依赖S9的致突变剂。所研究的所有化合物的直接作用和依赖S9的致突变性在OAT高产菌株中均增强，而在OAT缺陷菌株中则大大降低（尽管并非总是完全丧失），这表明OAT会放大这些化合物的基因毒性表达。1-乙酰氨基芘-6-醇为了表现出任何致突变性既需要S9也需要OAT活性；这一发现强烈表明，与进一步的S9催化的环氧化相反，N-羟基化随后进行O-酯化是1-硝基芘尿液代谢产物的主要活化途径。
