Elbarbry Fawzy A, McNamara Patrick J, Alcorn Jane
College of Pharmacy and Nutrition, University of Saskatchewan, Saskatoon, Saskatchewan, Canada S7N5C9.
J Biochem Mol Toxicol. 2007;21(1):41-50. doi: 10.1002/jbt.20156.
We report a comprehensive examination of rat hepatic CYP1A2 and CYP2E1 ontogeny. We compare the data to human data to determine the rat's capacity as a model to identify CYP-mediated mechanisms underlying age-dependent differences in susceptibility to toxicity. We evaluated CYP expression using real-time RT-PCR, immunoblot and immunohistochemistry, and specific probe activity in male rat livers (n = 4) at critical developmental life stages. CYP2E1 mRNA expression was low at birth, then increased rapidly to peak prior to weaning. CYP1A2 transcript levels remained very low postnatally and then increased dramatically to reach peak expression during weaning. Immunoreactive CYP1A2 and CYP2E1 was first detected at postnatal day 3 (PD3), and reached 50% of adult levels after weaning, and adult levels by puberty. CYP1A2 and CYP2E1 probe activity (pmol/(min mg)) was detected at PD3 and peaked during weaning and late neonatal period, respectively. CYP activity fell to adult values by puberty, a pattern that closely mirrored the temporal changes in mRNA but not protein. An increasing preferential localization of CYP1A2 and CYP2E1 immunoreactivity in perivenous hepatocytes was observed with maturation to adulthood. Although differences in CYP1A2 and CYP2E1 ontogeny between rats and humans exist, knowledge of these differences will aid interspecies extrapolation of developmental toxicokinetic data.
我们报告了对大鼠肝脏CYP1A2和CYP2E1个体发生的全面研究。我们将这些数据与人类数据进行比较，以确定大鼠作为模型来识别毒性易感性年龄依赖性差异背后的CYP介导机制的能力。我们在雄性大鼠肝脏（n = 4）的关键发育生命阶段，使用实时RT-PCR、免疫印迹和免疫组织化学评估CYP表达以及特定探针活性。CYP2E1 mRNA表达在出生时较低，然后在断奶前迅速增加至峰值。CYP1A2转录水平在出生后一直很低，然后在断奶期间急剧增加以达到峰值表达。免疫反应性CYP1A2和CYP2E1在出生后第3天（PD3）首次检测到，断奶后达到成年水平的50%，到青春期达到成年水平。CYP1A2和CYP2E1探针活性（pmol/(min mg)）在PD3时检测到，分别在断奶期和新生儿后期达到峰值。CYP活性在青春期降至成年值，这种模式与mRNA的时间变化密切相关，但与蛋白质的时间变化不同。随着成熟至成年，观察到CYP1A2和CYP2E1免疫反应性在肝小叶静脉周围肝细胞中的优先定位增加。尽管大鼠和人类之间存在CYP1A2和CYP2E1个体发生的差异，但了解这些差异将有助于种间外推发育毒代动力学数据。
