Zijlstra J A, Vogel E W
Department of Radiation Genetics and Chemical Mutagenesis, University of Leiden, Sylvius Laboratories, The Netherlands.
Mutat Res. 1988 Nov;202(1):251-67. doi: 10.1016/0027-5107(88)90188-1.
It is determined to what extent certain inhibitors of the xenobiotic metabolizing enzyme systems have an influence on the mutagenicity of various pro-mutagens in Drosophila. 1-Phenylimidazole (PhI) is used as an inhibitor of the cytochrome P-450 (P-450) mediated monooxygenase activities. Iproniazid (Ipr) is a typical monoamine oxidase (MAO) inhibitor which as well seems capable of inhibiting to a certain extent P-450 mediated metabolism. N, N-Dimethyl benzylamine (N, N-DMB) is used as a competitive substrate for the N-oxidizing flavin-containing dimethylaniline monooxygenase (FDMAM). The enzyme-inhibiting activities of PhI and Ipr were determined in vitro using microsomes obtained from Drosophila larvae and adults. Both compounds were capable of inhibiting benzo[a]pyrene (BP) hydroxylation and p-nitroanisole (p-NA) demethylation, although for Ipr 100-fold higher concentrations were required compared to PhI. As model-mutagens were used: the nitrosamines dimethylnitrosamine (DMN) and diethylnitrosamine (DEN), the triazenes 1-(2,4,6-trichlorophenyl)-3,3-dimethyltriazene (Cl3PDMT), 1-(3-pyridyl)-3,3-dimethyltriazene (PyDMT) and dacarbazine (DTIC), the hydrazines procarbazine (PCZ), 1,1-dimethylhydrazine (1,1-DMH) and 1,2-dimethylhydrazine (1,2-DMH) as well as the pyrrolizidine alkaloid seniciphylline (SPh). Simultaneous or pretreatment with Ipr results in a clear decrease of the mutagenicity of Cl3PDMT, while PhI pretreatment leads to an increased mutagenicity. This indicates that these two inhibitors do not inhibit the same enzyme or isozyme. For SPh too, Ipr pretreatment results in some decrease of the mutagenicity. This is in contrast to DEN, where the activation is clearly inhibited by PhI while Ipr has only a minor effect. For DMN, DTIC and PCZ both Ipr and PhI pretreatment caused considerable decreases of the mutagenicity. Inhibition of the FDMAM catalyzed activity by N,N-DMB resulted in an increase of mutagenicity with Cl3PDMT, in a moderate decrease of mutagenicity with DTIC, and a marked decrease with DMN, which was strongly inhibited. In contrast to the clear-cut mutagenicity of PCZ, 1,1-DMH and 1,2-DMH are not mutagenic in Drosophila. No change was observed upon inhibition of the various metabolizing activities. Apart from using strain differences in metabolizing activities and enzyme induction, enzyme inhibition can also be used to determine the influence of metabolism on the in vivo mutagenicity of promutagens in Drosophila.
研究确定了某些外源性生物代谢酶系统抑制剂对果蝇中各种前诱变剂的诱变性有多大程度的影响。1-苯基咪唑（PhI）用作细胞色素P-450（P-450）介导的单加氧酶活性的抑制剂。异烟肼（Ipr）是一种典型的单胺氧化酶（MAO）抑制剂，它似乎也能够在一定程度上抑制P-450介导的代谢。N，N-二甲基苄胺（N，N-DMB）用作含黄素的二甲基苯胺单加氧酶（FDMAM）N-氧化的竞争性底物。使用从果蝇幼虫和成虫获得的微粒体在体外测定PhI和Ipr的酶抑制活性。两种化合物都能够抑制苯并[a]芘（BP）羟基化和对硝基苯甲醚（p-NA）去甲基化，尽管与PhI相比，Ipr需要高100倍的浓度。使用的模型诱变剂有：亚硝胺二甲基亚硝胺（DMN）和二乙基亚硝胺（DEN）、三氮烯1-(2,4,6-三氯苯基)-3,3-二甲基三氮烯（Cl3PDMT）、1-(3-吡啶基)-3,3-二甲基三氮烯（PyDMT）和达卡巴嗪（DTIC）、肼丙卡巴肼（PCZ）、1,1-二甲基肼（1,1-DMH）和1,2-二甲基肼（1,2-DMH）以及吡咯里西啶生物碱千里光叶碱（SPh）。Ipr同时使用或预处理会导致Cl3PDMT的诱变性明显降低，而PhI预处理会导致诱变性增加。这表明这两种抑制剂抑制的不是同一种酶或同工酶。对于SPh，Ipr预处理也会导致诱变性有所降低。这与DEN形成对比，在DEN中，PhI明显抑制其活化，而Ipr只有轻微影响。对于DMN、DTIC和PCZ，Ipr和PhI预处理都会导致诱变性显著降低。N，N-DMB对FDMAM催化活性的抑制导致Cl3PDMT的诱变性增加，DTIC的诱变性适度降低，DMN的诱变性显著降低，DMN受到强烈抑制。与PCZ明确的诱变性不同，1,1-DMH和1,2-DMH在果蝇中没有诱变性。抑制各种代谢活性后未观察到变化。除了利用代谢活性和酶诱导方面的品系差异外，酶抑制也可用于确定代谢对果蝇体内前诱变剂诱变性的影响。
