Herber R, Hercelin B, Van Cantfort J, De Graeve J, Fournel-Gigleux S, Taguchi T, Magdalou J
Centre du Médicament, Nancy, France.
Drug Metab Dispos. 1995 Dec;23(12):1305-14.
Reduction and glucuronidation of the vasoprotectant drug, naftazone, by human and rat liver microsomes and by recombinant UDP-glucuronosyltransferases (UGT) stably expressed in V79 cells were studied. The oxo group was first reduced in the presence of NADPH or NADH, and was subsequently readily glucuronidated on the phenolic moiety leading to a 1 beta-O-glucuronide, as revealed from MS and by proton and 13C-NMR. Glucuronide extracted from the urine of rats treated with the drug presented the same structure. In all enzyme systems tested, NADH was the most efficient electron donor, when compared with NADPH. The reaction was strongly inhibited by quercitrin, a specific inhibitor of carbonyl reductase. Attempts to isolate the reduced intermediate were unsuccessful because of its marked instability. In humans, a large interindividual variation for the formation of glucuronide was observed with microsomes of seven different liver samples (3.98 +/- 3.22 nmol/min.mg). In rat, glucuronidation of reduced naftazone was strongly induced (12-fold) by 3-methylcholanthrene and, to a lesser extent (2.6-fold) by phenobarbital, but was not affected by clofibrate. In addition, liver microsomes from Gunn rats, which present a genetic defect in bilirubin and phenol UGTs could not form glucuronide of reduced naftazone. The drug, after addition of NADH, was a substrate of the human liver recombinant UGT16 that presents a strict specificity toward planar phenolic substances, but not that of UGT2B4 and UGT2B1 expressed in V79 fibroblasts. The reducing step by the endogenous V79 cellular reductase was rate-limiting. In conclusion, the powerful inducing effect exerted by 3-methylcholanthrene, the lack of glucuronidation in the Gunn rat and the ability of UGT16 encoded by the UGT1 gene to glucuronidate reduced naftazone suggest that, in humans and in the rat, the compound is metabolized by a UGT isoform (UGT1*6 and the rat orthologous form) belonging to family 1, with a restricted specificity toward the drug.
研究了人及大鼠肝微粒体以及在V79细胞中稳定表达的重组UDP - 葡萄糖醛酸基转移酶（UGT）对血管保护剂萘他唑酮的还原和葡萄糖醛酸化作用。在NADPH或NADH存在下，羰基首先被还原，随后酚羟基部分易于葡萄糖醛酸化，生成1β - O - 葡萄糖醛酸苷，这通过质谱以及质子和13C - NMR得以证实。从用该药物处理的大鼠尿液中提取的葡萄糖醛酸苷具有相同结构。在所有测试的酶系统中，与NADPH相比，NADH是最有效的电子供体。该反应受到羰基还原酶的特异性抑制剂槲皮苷的强烈抑制。由于还原中间体的显著不稳定性，分离该中间体的尝试未成功。在人类中，观察到七个不同肝脏样本的微粒体在葡萄糖醛酸苷形成方面存在较大个体差异（3.98±3.22 nmol/min·mg）。在大鼠中，3 - 甲基胆蒽强烈诱导（12倍）还原萘他唑酮的葡萄糖醛酸化，苯巴比妥诱导作用较小（2.6倍），但氯贝丁酯对其无影响。此外，患有胆红素和酚UGT基因缺陷的Gunn大鼠的肝微粒体不能形成还原萘他唑酮的葡萄糖醛酸苷。添加NADH后，该药物是人肝脏重组UGT16的底物，UGT16对平面酚类物质具有严格特异性，但不是V79成纤维细胞中表达的UGT2B4和UGT2B1的底物。内源性V79细胞还原酶的还原步骤是限速步骤。总之，3 - 甲基胆蒽的强大诱导作用、Gunn大鼠中缺乏葡萄糖醛酸化以及UGT1基因编码的UGT16对还原萘他唑酮进行葡萄糖醛酸化的能力表明，在人和大鼠中，该化合物由属于1家族的UGT同工型（UGT16和大鼠同源形式）代谢，对该药物具有有限的特异性。
