Noort D, Meijer E A, Visser T J, Meerman J H, Van der Marel G A, Van Boom J H, Mulder G J
Division of Toxicology, University of Leiden, The Netherlands.
Mol Pharmacol. 1991 Aug;40(2):316-20.
2,2,2-Triphenylethyl-UDP (TPEU) was synthesized as an analogue of the transition state of the glucuronidation reaction catalyzed by UDP-glucuronosyltransferase; it contains both a uridine and an acceptor substrate moiety. It inhibits rat liver microsomal UDP-glucuronosyltransferase [Eur. J. Biochem. 188:309-312 (1990)]. In the present work, TPEU was tested as an inhibitor of glucuronidation in intact rat hepatocytes. Two phenols (harmol and 3,3',5-triiodothyronine) and a hydroxamic acid (N-hydroxy-2-acetylaminofluorene) were used as substrates for glucuronidation. The glucuronidation of these substrates was strongly decreased by TPEU at 0.3-5 mM. Up to 5 mM TPEU did not kill the cells, as shown by unimpaired trypan blue exclusion at the end of the incubation. When glucuronidation was inhibited, the sulfation of harmol increased, as did the production of reactive species generated from N-hydroxy-2-acetylaminofluorene that bind to cellular macromolecules. This indicates that a decreased substrate consumption by loss of glucuronidation leads to increased conversion by competing pathways. The results show, therefore, that TPEU is an effective inhibitor of glucuronidation in this cellular system in vitro.
2,2,2-三苯乙基-UDP（TPEU）是作为由UDP-葡糖醛酸基转移酶催化的葡糖醛酸化反应过渡态的类似物合成的；它同时含有一个尿苷和一个受体底物部分。它能抑制大鼠肝脏微粒体UDP-葡糖醛酸基转移酶[《欧洲生物化学杂志》188:309 - 312（1990）]。在本研究中，TPEU被作为完整大鼠肝细胞中葡糖醛酸化的抑制剂进行测试。两种酚类物质（哈尔满和3,3',5-三碘甲状腺原氨酸）以及一种异羟肟酸（N-羟基-2-乙酰氨基芴）被用作葡糖醛酸化的底物。在0.3 - 5 mM浓度下，TPEU能强烈降低这些底物的葡糖醛酸化。高达5 mM的TPEU并未杀死细胞，孵育结束时台盼蓝拒染未受影响即表明了这一点。当葡糖醛酸化被抑制时，哈尔满的硫酸化增加，从N-羟基-2-乙酰氨基芴产生的与细胞大分子结合的活性物质的生成也增加。这表明葡糖醛酸化丧失导致底物消耗减少，进而通过竞争途径使转化率增加。因此，结果表明TPEU在这个体外细胞系统中是葡糖醛酸化的有效抑制剂。
