Oesch F, Metzler M, Fabian E, Kamp H, Bernshausen T, Damm G, Triebel S, Döhmer J, Landsiedel R, Van Ravenzwaay B
Institute of Toxicology, University of Mainz, Wackernheim D-55263, Germany.
Xenobiotica. 2010 Jan;40(1):72-82. doi: 10.3109/00498250903353464.
The in vitro mammalian metabolism of the fungicide zoxamide is related to its in vitro mammalian toxicity. After incubation of zoxamide with rat liver microsomes leading to practically 100% metabolism (mostly hydroxylated zoxamide), the cytotoxicity (methyl thiazole tetrazolium (MTT) test) and the mitosis-inhibiting potential (shown by cell count and by cell cycle analysis) for V79 were not distinguishable from those of zoxamide, demonstrating that the hydroxylation of zoxamide did not change the cytotoxicity or mitosis-inhibiting potential as determined by these assays. After incubation of zoxamide with rat liver S9 predominantly leading to conjugation with glutathione, and after incubation of zoxamide with rat liver slices predominantly leading to the glucuronide of the hydroxylated zoxamide, these activities were eliminated demonstrating that the glutathione conjugate and the glucuronide had lost the activities in these assays due either to no intrinsic potential of these conjugates or to their inability to penetrate the plasma membrane of mammalian cells. It is concluded that the metabolic hydroxylation of zoxamide did not change its activity in the assays used for investigating its influence on cell proliferation, cell cycle and cytotoxicity, while the formation of conjugates with glutathione or glucuronic acid led to the apparent loss of these activities. Thus, with zoxamide as a prototype, it was shown that, in principle, mammalian metabolism and its relationship to mammalian detoxication of fungicidal mitosis inhibitors may be reasonably anticipated from in vitro studies. In addition, the results provide a rational for the observed absence of typically mitosis inhibition-associated toxicities of zoxamide in mammals in vivo.
杀菌剂唑菌酰胺的体外哺乳动物代谢与其体外哺乳动物毒性相关。唑菌酰胺与大鼠肝微粒体孵育后，几乎100%发生代谢（主要为羟基化唑菌酰胺），此时V79细胞的细胞毒性（甲基噻唑四氮唑（MTT）试验）和有丝分裂抑制潜力（通过细胞计数和细胞周期分析显示）与唑菌酰胺本身的情况无明显差异，这表明唑菌酰胺的羟基化并未改变这些检测方法所测定的细胞毒性或有丝分裂抑制潜力。唑菌酰胺与大鼠肝脏S9孵育后主要生成谷胱甘肽结合物，与大鼠肝切片孵育后主要生成羟基化唑菌酰胺的葡萄糖醛酸苷，这些活性均消失，这表明谷胱甘肽结合物和葡萄糖醛酸苷在这些检测中失去活性，原因可能是这些结合物本身没有内在活性，或者是它们无法穿透哺乳动物细胞的质膜。研究得出结论，唑菌酰胺的代谢羟基化在用于研究其对细胞增殖、细胞周期和细胞毒性影响的检测中并未改变其活性，而与谷胱甘肽或葡萄糖醛酸形成结合物导致这些活性明显丧失。因此，以唑菌酰胺为原型表明，原则上，从体外研究中可以合理预测哺乳动物代谢及其与杀真菌有丝分裂抑制剂的哺乳动物解毒作用之间的关系。此外，这些结果为唑菌酰胺在体内哺乳动物中未观察到典型的与有丝分裂抑制相关的毒性提供了合理依据。
