Izukawa Takeshi, Nakajima Miki, Fujiwara Ryoichi, Yamanaka Hiroyuki, Fukami Tatsuki, Takamiya Masataka, Aoki Yasuhiro, Ikushiro Shin-ichi, Sakaki Toshiyuki, Yokoi Tsuyoshi
Drug Metabolism and Toxicology, Faculty of Pharmaceutical Sciences, Kanazawa University, Kakuma-machi, Kanazawa, Japan.
Drug Metab Dispos. 2009 Aug;37(8):1759-68. doi: 10.1124/dmd.109.027227. Epub 2009 May 13.
UDP-glucuronosyltransferases (UGTs) catalyze glucuronidation of a variety of xenobiotics and endobiotics. UGTs are divided into two families, UGT1 and UGT2. The purpose of this study was to estimate the absolute expression levels of each UGT isoform in human liver and to evaluate the interindividual variability. Real-time reverse transcriptase-polymerase chain reaction analysis was performed to determine the copy numbers of nine functional UGT1A isoforms and seven UGT2B isoforms. We noticed that not only primers but also templates as a standard for quantification should prudently be selected. Once we established appropriate conditions, the mRNA levels of each UGT isoform in 25 individual human livers were determined. UGT1A1 (0.9-138.5), UGT1A3 (0.1-66.6), UGT1A4 (0.1-143.3), UGT1A6 (1.0-70.4), UGT1A9 (0.3-132.4), UGT2B4 (0.3-615.0), UGT2B7 (0.2-97.4), UGT2B10 (0.7-253.2), UGT2B15 (0.3-107.8), and UGT2B17 (0.5-157.1) were substantially expressed (x10(4) copy/mug RNA) with large interindividual variability. Abundant isoforms were UGT2B4 and UGT2B10, followed by UGT1A1, UGT2B15, and UGT1A6. The sum of the UGT2B mRNA levels was higher than that of UGT1A mRNA levels. It is interesting to note that the mRNA levels normalized with glyceraldehyde-3-phosphate dehydrogenase mRNA for almost UGT isoforms that are substantially expressed in liver showed significant correlations to each other. Western blot analysis was performed using antibodies specific for UGT1A1, UGT1A4, UGT1A6, or UGT2B7. Correlation between the protein and mRNA levels was observed in only UGT1A1 (r = 0.488; p < 0.01). In conclusion, this study comprehensively determined the absolute values of mRNA expression of each UGT isoform in human livers and found considerable interindividual variability.
尿苷二磷酸葡萄糖醛酸基转移酶（UGTs）催化多种外源性和内源性物质的葡萄糖醛酸化反应。UGTs分为两个家族，即UGT1和UGT2。本研究的目的是评估人肝脏中各UGT同工型的绝对表达水平，并评估个体间的变异性。采用实时逆转录-聚合酶链反应分析来确定9种功能性UGT1A同工型和7种UGT2B同工型的拷贝数。我们注意到，不仅引物，而且作为定量标准的模板都应谨慎选择。一旦我们建立了合适的条件，就测定了25个人类肝脏中各UGT同工型的mRNA水平。UGT1A1（0.9 - 138.5）、UGT1A3（0.1 - 66.6）、UGT1A4（0.1 - 143.3）、UGT1A6（1.0 - 70.4）、UGT1A9（0.3 - 132.4）、UGT2B4（0.3 - 615.0）、UGT2B7（0.2 - 97.4）、UGT2B10（0.7 - 253.2）、UGT2B15（0.3 - 107.8）和UGT2B17（0.5 - 157.1）均有大量表达（x10(4)拷贝/μg RNA），个体间差异较大。丰富的同工型为UGT2B4和UGT2B10，其次是UGT1A1、UGT2B15和UGT1A6。UGT2B mRNA水平的总和高于UGT1A mRNA水平。值得注意的是，几乎所有在肝脏中大量表达的UGT同工型，以甘油醛-3-磷酸脱氢酶mRNA标准化后的mRNA水平彼此之间显示出显著相关性。使用针对UGT1A1、UGT1A4、UGT1A6或UGT2B7的特异性抗体进行蛋白质免疫印迹分析。仅在UGT1A1中观察到蛋白质水平与mRNA水平之间存在相关性（r = 0.488；p < 0.01）。总之，本研究全面测定了人肝脏中各UGT同工型mRNA表达的绝对值，并发现个体间存在相当大的变异性。
