Sequential Metabolism of Secondary Alkyl Amines to Metabolic-Intermediate Complexes: Opposing Roles for the Secondary Hydroxylamine and Primary Amine Metabolites of Desipramine, (<i>S</i>)-Fluoxetine, and <i>N-</i>Desmethyldiltiazem
作者:Kelsey L. Hanson、Brooke M. VandenBrink、Kantipudi N. Babu、Kyle E. Allen、Wendel L. Nelson、Kent L. Kunze
DOI:10.1124/dmd.110.032391
日期:2010.6
Three secondary amines desipramine (DES), ( S )-fluoxetine [( S )-FLX], and N -desmethyldiltiazem (MA) undergo N -hydroxylation to the corresponding secondary hydroxylamines [ N -hydroxydesipramine, ( S )- N -hydroxyfluoxetine, and N -hydroxy- N -desmethyldiltiazem] by cytochromes P450 2C11, 2C19, and 3A4, respectively. The expected primary amine products, N -desmethyldesipramine, ( S )-norfluoxetine, and N,N -didesmethyldiltiazem, are also observed. The formation of metabolic-intermediate (MI) complexes from these substrates and metabolites was examined. In each example, the initial rates of MI complex accumulation followed the order secondary hydroxylamine > secondary amine ≫ primary amine, suggesting that the primary amine metabolites do not contribute to formation of MI complexes from these secondary amines. Furthermore, the primary amine metabolites, which accumulate in incubations of the secondary amines, inhibit MI complex formation. Mass balance studies provided estimates of the product ratios of N -dealkylation to N -hydroxylation. The ratios were 2.9 (DES-CYP2C11), 3.6 [( S )-FLX-CYP2C19], and 0.8 (MA-CYP3A4), indicating that secondary hydroxylamines are significant metabolites of the P450-mediated metabolism of secondary alkyl amines. Parallel studies with N -methyl-d3-desipramine and CYP2C11 demonstrated significant isotopically sensitive switching from N -demethylation to N -hydroxylation. These findings demonstrate that the major pathway to MI complex formation from these secondary amines arises from N -hydroxylation rather than N -dealkylation and that the primary amines are significant competitive inhibitors of MI complex formation.
三种仲胺去甲丙咪嗪(DES)、(S)-氟西汀[(S)-FLX]和N-去甲基地尔硫卓(MA)分别经细胞色素P450 2C11、2C19和3A4催化进行N-羟基化反应,生成相应的仲羟基胺[N-羟基去甲丙咪嗪、(S)-N-羟基氟西汀和N-羟基-N-去甲基地尔硫卓]。同时,也观察到了预期的伯胺产物:N-去甲基去甲丙咪嗪、(S)-去甲氟西汀和N,N-二去甲基地尔硫卓。研究了这些底物和代谢物形成代谢中间体(MI)复合物的过程。在每种情况下,MI复合物积累的初始速率遵循仲羟基胺 > 仲胺 ≫ 伯胺的顺序,表明伯胺代谢物不参与这些仲胺形成MI复合物的过程。此外,在仲胺孵育中积累的伯胺代谢物抑制MI复合物的形成。质量平衡研究表明,N-脱烷基化与N-羟基化的产物比例估计为2.9(DES-CYP2C11)、3.6[(S)-FLX-CYP2C19]和0.8(MA-CYP3A4),表明仲羟基胺是P450介导的仲烷基胺代谢的重要代谢物。与N-甲基-d3-去甲丙咪嗪和CYP2C11的平行研究表明,存在从N-脱甲基化到N-羟基化的显著同位素敏感性转换。这些发现表明,这些仲胺形成MI复合物的主要途径来自N-羟基化而非N-脱烷基化,并且伯胺是MI复合物形成的显著竞争性抑制剂。