Mechanism of metabolic activation of the analgetic bucetin to bacterial mutagens by hamster liver microsomes.
作者:TAKEHIKO NOHMI、MOTOI JR. ISHIDATE、AKIRA HIRATSUKA、TADASHI WATABE
DOI:10.1248/cpb.33.2877
日期:——
Bucetin (N-(β-hydroxybutyryl)-p-phenetidine) was found to be mutagenic to Salmonella typhimurium TA100 in the presence of liver 9000g supernatant fractions (S9) prepared from polychlorinated biphenyl (PCB)-treated hamsters and a reduced nicotinamide adenine dinucleotidephosphate (NADPH)-generating system. However, the analgetic was not mutagenic in the presence of NADPH-fortified S9 from PCB-treated rat liver. The mutagenic potency of bucetin was about a quarter of that of the structurally related analgetic, phenacetin. PCB-treated hamster liver microsomes fortified with NADPH activated bucetin to two direct-acting mutagens, N-hydroxyphenetidine and p-nitrosophenetole, through deacylation followed by N-hydroxylation. The nitroso compound arose from N-hydroxyphenetidine via autoxidation. N-(β-Hydroxybutyryl)-p-aminophenol, a major metabolite of bucetin under the conditions used, was not mutagenic to TA 100 either with or without NADPH-fortified S9 from PCB-treated or untreated rats or hamsters. N-Hydroxybucetin, which was about 70 times less mutagenic than N-hydroxyphenacetin in the presence of PCB-treated hamster S9, was not detected as a metabolite of bucetin from the NADPH-fortified reaction mixtures. Although no species difference was observed in p-phenetidine N-hydroxylation, the rate of bucetin deacylation was over 90 times higher in hamsters than in rats. The rate of microsomal deacylation of bucetin was much lower than that of phenacetin or N-butyryl-p-phenetidine. These results suggest that the species difference in bucetin mutagenicity is due to the difference in deacylating activity between rat and hamster liver microsomes, and also that the β-hydroxyl group in the butyryl side chain makes bucetin poorly hydrolyzable in microsomes, resulting in lower mutagenic activity as compared with phenacetin.
研究发现,在多氯联苯(PCB)处理仓鼠肝脏 9000g 上清液馏分(S9)和还原型烟酰胺腺嘌呤二核苷酸(NADPH)生成系统存在的情况下,Bucetin(N-(β-羟基丁酰)-p-苯乙啶)对鼠伤寒沙门氏菌 TA100 具有诱变作用。然而,在来自经多氯联苯(PCB)处理的大鼠肝脏的强化 NADPH S9 存在的情况下,该镇痛剂不具有诱变性。布塞汀的诱变效力约为结构相关的镇痛药苯乙哌啶的四分之一。经 NADPH 强化的多氯联苯处理仓鼠肝脏微粒体通过脱乙酰化和 N-羟基化将布克汀活化为两种直接作用的诱变剂--N-羟基苯乙啶和对亚硝基苯乙醚。亚硝基化合物是由 N-羟基苯乙啶通过自氧化作用生成的。在使用条件下,N-(β-羟基丁酰)-p-氨基苯酚是丁香酚的主要代谢物,无论是否添加 NADPH 强化 S9,都不会对来自 PCB 处理过或未处理过的大鼠或仓鼠的 TA 100 产生诱变作用。在有 PCB 处理过的仓鼠 S9 存在的情况下,N-羟基白屈菜素的诱变性比 N-羟基苯乙酮低约 70 倍,但在 NADPH 强化的反应混合物中未检测到白屈菜素的代谢物。虽然在对苯乙啶 N-羟基化过程中没有观察到物种差异,但仓鼠的丁香酚脱乙酰率比大鼠高 90 多倍。与苯乙酸或 N-丁酰基对苯乙哌啶相比,丁香酮苷的微粒体脱乙酰率要低得多。这些结果表明,布塞汀致突变性的物种差异是由于大鼠和仓鼠肝脏微粒体的脱乙酰活性不同造成的,而且丁酰侧链中的β-羟基使布塞汀在微粒体中的水解性差,导致其致突变活性低于苯乙哌啶。