Developmental expression of the major human hepatic CYP3A enzymes
Developmental expression of the major human hepatic CYP3A enzymes
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DOI：
10.1124/jpet.103.054841
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发表时间：
2003-11-01
影响因子：
3.5
通讯作者：
Zaya, MJ
中科院分区：
文献类型：
--
作者：
Stevens, JC;Hines, RN;Zaya, MJ
人类细胞色素P4503A表现出受发育影响的表达模式。CYP3A7和CYP3A4通常分别被归类为胎儿和成人肝脏的主要形式。然而，由于缺乏CYP3A异构体特异性抗体或标记酶活性，CYP3A4、-3A5和-3A7发育表达的表征一直很混乱。因此，本研究的目的是利用多达212个胎儿和儿童肝脏样本来表征从妊娠早期到18岁的肝脏CYP3A形式的发育表达。基于免疫定量，CYP3A5蛋白表达变化很大，通常与年龄无关，在非裔美国人中更常见。为了区分CYP3A4和-3A7水平，对CYP3A表达形式的脱氢表雄酮代谢物模式进行了表征，并用于肝微粒体样品中蛋白质的同时定量。CYP3A4主要代谢产物为7 -羟基脱氢表雄酮，质谱与标准品相匹配。动力学分析显示CYP3A4对7 -羟基-脱氢表雄酮的内在清除率比-3A7高34倍，而CYP3A7对16 -羟基-脱氢表雄酮的内在清除率最高。表达酶的代谢物谱符合多反应模型，并计算胎儿和儿童肝微粒体样本中CYP3A4和-3A7的水平。胎儿肝微粒体CYP3A7水平极高（311-158 pmol/mg蛋白），并在出生后6个月显著表达。胎儿肝脏CYP3A4低表达（小于或等于10 pmol/mg），平均水平随着出生后年龄的增加而增加。
The human cytochrome P4503A forms show expression patterns subject to developmental influence. CYP3A7 and CYP3A4 are generally classified as the major fetal and adult liver forms, respectively. However, characterization of CYP3A4, -3A5, and -3A7 developmental expression has historically been confounded by the lack of CYP3A isoform-specific antibodies or marker enzyme activities. Therefore, the objective of this study was to characterize the developmental expression of hepatic CYP3A forms from early gestation to 18 years of age using up to 212 fetal and pediatric liver samples. Based on immunoquantitation, CYP3A5 protein expression was found to be highly variable, generally independent of age, and more frequently observed for African-American individuals. For differentiation of CYP3A4 and -3A7 levels, dehydroepiandrosterone metabolite patterns for expressed CYP3A forms were characterized and used for simultaneous quantitation of protein within liver microsome samples. The major metabolite formed by CYP3A4, 7beta-hydroxy-dehydroepiandrosterone, was identified based on cochromatography and mass spectra matching with the authentic standard. Kinetic analysis showed a 34-fold greater intrinsic clearance of 7beta-hydroxy-dehydroepiandrosterone by CYP3A4 versus -3A7, whereas CYP3A7 showed the highest 16alpha-hydroxy-dehydroepiandrosterone intrinsic clearance. Metabolite profiles for the expressed enzymes were fit to a multiple response model and CYP3A4 and -3A7 levels in fetal and pediatric liver microsome samples were calculated. Fetal liver microsomes showed extremely high CYP3A7 levels (311-158 pmol/mg protein) and significant expression through 6 months postnatal age. Low CYP3A4 expression was noted for fetal liver (less than or equal to10 pmol/mg), with mean levels increasing with postnatal age.