Perloff M D, von Moltke L L, Court M H, Kotegawa T, Shader R I, Greenblatt D J
Department of Pharmacology, Tufts University School of Medicine, Boston, Massachusetts, USA.
J Pharmacol Exp Ther. 2000 Feb;292(2):618-28.
Midazolam (MDZ) and triazolam (TRZ) hydroxylation, reactions considered to be cytochrome P-4503A (CYP3A)-mediated in humans, were examined in mouse and human liver microsomes. In both species, alpha- and 4-hydroxy metabolites were the principal products. Western blotting with anti-CYP3A1 antibody detected a single band of immunoreactive protein in both human and mouse samples: 0.45 +/- 0. 12 and 2.02 +/- 0.24 pmol/mg protein (mean +/- S.E., n = 3), respectively. Ketoconazole potently inhibited MDZ and TRZ metabolite formation in human liver microsomes (IC(50) range, 0.038-0.049 microM). Ketoconazole also inhibited the formation of both TRZ metabolites and of 4-OH-MDZ formation in mouse liver microsomes (IC(50) range, 0.0076-0.025 microM). However, ketoconazole (10 microM) did not produce 50% inhibition of alpha-OH-MDZ formation in mouse liver microsomes. Anti-CYP3A1 antibodies produced concentration-dependent inhibition of MDZ and TRZ metabolite formation in human liver microsomes and of TRZ metabolite and 4-OH-MDZ formation in mouse liver microsomes to less than 20% of control values but reduced alpha-OH-MDZ formation to only 66% of control values in mouse liver microsomes. Anti-CYP2C11 antibodies inhibited alpha-OH-MDZ metabolite formation in a concentration-dependent manner to 58% of control values in mouse liver microsomes but did not inhibit 4-OH-MDZ formation. Thus, TRZ hydroxylation appears to be CYP3A specific in mice and humans. alpha-Hydroxylation of MDZ has a major CYP2C component in addition to CYP3A in mice, demonstrating that metabolic profiles of drugs in animals cannot be assumed to reflect human metabolic patterns, even with closely related substrates.
在小鼠和人肝微粒体中研究了咪达唑仑（MDZ）和三唑仑（TRZ）的羟基化反应，这两种反应在人体内被认为是由细胞色素P-4503A（CYP3A）介导的。在这两个物种中，α-羟基和4-羟基代谢产物都是主要产物。用抗CYP3A1抗体进行的蛋白质免疫印迹检测到人和小鼠样品中均有一条免疫反应性蛋白条带：分别为0.45±0.12和2.02±0.24 pmol/mg蛋白（平均值±标准误，n = 3）。酮康唑能有效抑制人肝微粒体中MDZ和TRZ代谢产物的形成（IC50范围为0.038 - 0.049 μM）。酮康唑也抑制小鼠肝微粒体中TRZ代谢产物的形成以及4-OH-MDZ的形成（IC50范围为0.0076 - 0.025 μM）。然而，酮康唑（10 μM）并未对小鼠肝微粒体中α-OH-MDZ的形成产生50%的抑制作用。抗CYP3A1抗体在人肝微粒体中对MDZ和TRZ代谢产物的形成以及在小鼠肝微粒体中对TRZ代谢产物和4-OH-MDZ的形成产生浓度依赖性抑制，使其降至对照值的20%以下，但在小鼠肝微粒体中仅将α-OH-MDZ的形成降至对照值的66%。抗CYP2C11抗体以浓度依赖性方式将小鼠肝微粒体中α-OH-MDZ代谢产物的形成抑制至对照值的58%，但不抑制4-OH-MDZ的形成。因此，TRZ的羟基化在小鼠和人类中似乎具有CYP3A特异性。在小鼠中，MDZ的α-羟基化除了CYP3A外还有主要的CYP2C成分，这表明即使使用密切相关的底物，也不能假定动物体内药物的代谢谱能反映人类的代谢模式。
