Leeder J Steven, Gaedigk Roger, Marcucci Kenda A, Gaedigk Andrea, Vyhlidal Carrie A, Schindel Bradley P, Pearce Robin E
Section of Developmental Pharmacology and Experimental Therapeutics, Children's Mercy Hospital and Clinics, 2401 Gillham Road, Kansas City, MO 64108, USA.
J Pharmacol Exp Ther. 2005 Aug;314(2):626-35. doi: 10.1124/jpet.105.086504. Epub 2005 Apr 21.
Fetal liver CYP3A7 plays an important role in placental estriol synthesis during pregnancy, yet little is known concerning the extent or consequences of variability in expression. The purpose of this investigation was to characterize the variability in CYP3A7 expression using several phenotypic measures in a panel of 54 fetal livers ranging in age from 76 days to 32 weeks gestation. CYP3A7 mRNA expression was measured using quantitative polymerase chain reaction, whereas immunoreactive CYP3A7 was determined using an affinity-purified antipeptide antibody. Variability in catalytic activity was evaluated using testosterone and dehydroepiandrosterone (DHEA) as substrates. Across the entire panel, CYP3A7 was the most abundant CYP3A mRNA species present and varied 634-fold from 151 to 95,700 transcripts/ng total RNA, corrected for 18S ribosomal RNA. CYP3A4 expression was minimal based on mRNA expression (1000-fold lower than CYP3A7) and the ratio of testosterone 2alpha- (T2alphaH) to 6beta- (T6betaH) hydroxylation. T2alphaH and T6betaH were highly correlated (r(2) = 0.859), and the correlation increased (r(2) = 0.974) in livers with CYP3A5*3/3 genotypes implying that the same enzyme (CYP3A7) generated both products. Overall, T2alphaH and DHEA16alphaH activities varied 175- and 250-fold, respectively. A subset of five samples had extremely low mRNA, protein, and catalytic activity, possibly due to pathology affecting fetal viability (anencephaly, porencephaly). In the remaining samples, T2alphaH activity varied 6.7-fold (358 +/- 142, range 97 to 643 pmol/min/mg) and DHEA16alphaH activity varied 6.2-fold (8.07 +/- 2.87, range 2.41 to 14.9 nmol/min/mg). Observed variability in CYP3A7 activity was not related to CYP3A72, and alternative regulatory mechanisms require further investigation.
胎儿肝脏中的细胞色素P450 3A7（CYP3A7）在孕期胎盘雌三醇合成中起重要作用，但关于其表达变异性的程度及影响知之甚少。本研究旨在利用多种表型指标，对54例胎龄76天至32周的胎儿肝脏中CYP3A7的表达变异性进行特征分析。采用定量聚合酶链反应测定CYP3A7信使核糖核酸（mRNA）的表达，用亲和纯化的抗肽抗体测定免疫反应性CYP3A7。以睾酮和脱氢表雄酮（DHEA）为底物评估催化活性的变异性。在整个样本组中，CYP3A7是含量最丰富的CYP3A mRNA种类，经18S核糖体RNA校正后，其转录本含量在151至95,700个/纳克总RNA之间，相差634倍。基于mRNA表达（比CYP3A7低1000倍）以及睾酮2α-（T2αH）与6β-（T6βH）羟基化的比率，CYP3A4的表达量极少。T2αH和T6βH高度相关（r² = 0.859），在携带CYP3A5*3/3基因型的肝脏中相关性增加（r² = 0.974），这意味着同一酶（CYP3A7）产生这两种产物。总体而言，T2αH和DHEA 16αH活性分别相差175倍和250倍。有五个样本的子集mRNA、蛋白质和催化活性极低，可能是由于影响胎儿生存能力的病理状况（无脑儿、脑穿通畸形）所致。在其余样本中，T2αH活性相差6.7倍（358±142，范围97至643皮摩尔/分钟/毫克），DHEA 16αH活性相差6.2倍（8.07±2.87，范围2.41至14.9纳摩尔/分钟/毫克）。观察到的CYP3A7活性变异性与CYP3A72无关，其他调控机制有待进一步研究。
