Cnubben N H, van den Berg C L, Rietjens I M
Department of Biochemistry, Agricultural University, Dreijenlaan, Wageningen, The Netherlands.
Toxicol Appl Pharmacol. 1996 Dec;141(2):403-15. doi: 10.1006/taap.1996.0306.
The in vitro and in vivo metabolic profiles of a series of C4-substituted 2-fluoroanilines were determined and compared to their capacity to induce methemoglobinemia and nephrotoxicity in male Wistar rats. Qualitative and quantitative relationships between the biotransformation and the toxic endpoint of the halogenated anilines were defined. The rate of in vitro N-hydroxylation of the aniline derivatives correlated with the capacity of the compounds to induce methemoglobinemia (r = 0.96). In the experiments on the nephrotoxicity, attention was focused on the relative importance of the C4- and C6-hydroxylated metabolites of the C4-substituted 2-fluoroanilines. In vivo, the formation of 4-aminophenol metabolites was demonstrated to vary in the opposite order as the formation of the 6-aminophenol metabolites. 1H-NMR urinalysis and characterization of a set of conventional biochemical urinary parameters revealed the occurrence of nephrotoxicity upon exposure to the aniline derivatives and were most consistent with damage at the proximal tubular site. Comparison of the extent of nephrotoxicity to the extent of formation of the 4-aminophenol and/or 6-aminophenol metabolites, respectively, indicates a predominant role for the C4-hydroxylation route, not the C6-hydroxylation route, in the induction of nephrotoxic effects. Thus, a qualitative relationship is observed for the extent of C4-hydroxylation of the aniline derivatives and the extent of their in vivo nephrotoxicity. In addition, comparison of the extent of 4-aminophenol formation and nephrotoxicity of both 2-fluoroaniline and 2,4-difluoroaniline pointed at a possible role for a bioactivation pathway through oxidative dehalogenation, resulting in direct formation of a 1,4-benzoquinoneimine as the primary metabolite in the case of 2,4-difluoroaniline. Altogether, it is concluded that a decrease in C4-hydroxylation in the series of aniline derivatives results in a metabolic switch to C6- and N-hydroxylation and, consequently, a shift in the type of toxic endpoint observed, i.e., from nephrotoxicity to methemoglobinemia.
测定了一系列C4-取代的2-氟苯胺的体外和体内代谢谱，并将其与它们在雄性Wistar大鼠中诱导高铁血红蛋白血症和肾毒性的能力进行了比较。确定了卤代苯胺生物转化与毒性终点之间的定性和定量关系。苯胺衍生物的体外N-羟基化速率与化合物诱导高铁血红蛋白血症的能力相关（r = 0.96）。在肾毒性实验中，重点关注C4-取代的2-氟苯胺的C4-和C6-羟基化代谢物的相对重要性。在体内，4-氨基酚代谢物的形成与6-氨基酚代谢物的形成呈相反顺序变化。1H-NMR尿液分析和一组常规生化尿液参数的表征揭示了接触苯胺衍生物后肾毒性的发生，并且与近端肾小管部位的损伤最为一致。将肾毒性程度分别与4-氨基酚和/或6-氨基酚代谢物的形成程度进行比较，表明C4-羟基化途径而非C6-羟基化途径在诱导肾毒性作用中起主要作用。因此，观察到苯胺衍生物的C4-羟基化程度与其体内肾毒性程度之间存在定性关系。此外，对2-氟苯胺和2,4-二氟苯胺的4-氨基酚形成程度和肾毒性的比较表明，通过氧化脱卤的生物活化途径可能起作用，在2,4-二氟苯胺的情况下，导致直接形成1,醌亚胺作为主要代谢物。总之，得出的结论是，苯胺衍生物系列中C4-羟基化的减少导致代谢转向C6-和N-羟基化，因此，观察到的毒性终点类型发生转变，即从肾毒性转变为高铁血红蛋白血症。
