Weber G L, Sipes I G
Department of Pharmacology/Toxicology, College of Pharmacy, University of Arizona, Tucson 85721.
Toxicol Appl Pharmacol. 1992 Mar;113(1):152-8. doi: 10.1016/0041-008x(92)90020-s.
In vitro studies using rat and human hepatic microsomes have shown that the halogenated hydrocarbon 1,2,3-trichloropropane (TCP) is bioactivated to the direct acting mutagen 1,3-dichloroacetone (DCA). The presence of DCA in microsomal incubations was confirmed by gas chromatography-mass spectrometry. DCA formation was totally dependent on the presence of NADPH. The rate of DCA formation using rat and human microsomes was 0.268 +/- 0.029 and 0.026 +/- 0.006 nmol/min/mg protein +/- SE, respectively. When hepatic microsomes were isolated from rats pretreated with the cytochrome P-450 inducers, phenobarbital, and dexamethasone, 24- and 2.5-fold increases, respectively, in the rate of DCA production, were observed. Pretreatment with beta-naphthoflavone resulted in a 50% inhibition in DCA formation. The inhibitors of cytochromes P-450, SKF 525-A and 1-aminobenzotriazol, produced 85 and 70% inhibitions of DCA formation, respectively. When alcohol dehydrogenase and NADH were added to microsomal incubations, two TCP-related alcohols, 1,3-dichloro-2-propanol and 2,3-dichloropropanol, were formed. These alcohols are products of the initial microsomal metabolites, DCA and 2,3-dichloropropanal. [14C]TCP equivalents bound covalently to rat hepatic microsomal protein. This binding was increased 8-fold when hepatic microsomes from phenobarbital pretreated rats were used. The addition of either glutathione or N-acetylcysteine to the incubations completely inhibited this binding. In the presence of N-acetylcysteine, 1,3-(2-propanone)-bis-S-(N-acetylcysteine) (PDM) was the only N-acetylcysteine conjugate detected. It represented 87% of TCP microsomal metabolism. The formation of PDM implicates DCA as the major microsomal protein-binding metabolite of TCP. The formation of DCA, a direct-acting mutagen, may be responsible for the mutagenicity of TCP in systems using rat hepatic microsomes. Its role in the tumorigenicity and carcinogenicity of TCP remains to be established.
利用大鼠和人肝微粒体进行的体外研究表明，卤代烃1,2,3 - 三氯丙烷（TCP）可生物活化生成直接作用的诱变剂1,3 - 二氯丙酮（DCA）。通过气相色谱 - 质谱法证实了微粒体孵育中DCA的存在。DCA的形成完全依赖于NADPH的存在。使用大鼠和人微粒体时，DCA的形成速率分别为0.268±0.029和0.026±0.006 nmol/分钟/毫克蛋白±标准误。当从用细胞色素P - 450诱导剂苯巴比妥和地塞米松预处理的大鼠中分离肝微粒体时，观察到DCA生成速率分别增加了24倍和2.5倍。用β - 萘黄酮预处理导致DCA形成受到50%的抑制。细胞色素P - 450抑制剂SKF 525 - A和1 - 氨基苯并三唑分别对DCA形成产生85%和70%的抑制。当将乙醇脱氢酶和NADH添加到微粒体孵育体系中时，形成了两种与TCP相关的醇，即1,3 - 二氯 - 2 - 丙醇和2,3 - 二氯丙醇。这些醇是初始微粒体代谢产物DCA和2,3 - 二氯丙醛的产物。[14C]TCP等效物与大鼠肝微粒体蛋白共价结合。当使用来自苯巴比妥预处理大鼠的肝微粒体时，这种结合增加了8倍。向孵育体系中添加谷胱甘肽或N - 乙酰半胱氨酸可完全抑制这种结合。在N - 乙酰半胱氨酸存在下，1,3 -（2 - 丙酮）- 双 - S -（N - 乙酰半胱氨酸）（PDM）是唯一检测到的N - 乙酰半胱氨酸缀合物。它占TCP微粒体代谢的87%。PDM的形成表明DCA是TCP主要的微粒体蛋白结合代谢产物。直接作用诱变剂DCA的形成可能是TCP在使用大鼠肝微粒体的系统中具有诱变性的原因。其在TCP的致瘤性和致癌性中的作用仍有待确定。
