Lehman-McKeeman L D, Andrews G K, Klaassen C D
Department of Pharmacology, University of Kansas Medical Center, Kansas City 66103.
Toxicol Appl Pharmacol. 1988 Jan;92(1):10-7. doi: 10.1016/0041-008x(88)90222-0.
It is well established that hepatic concentrations of metallothioneins (MTs) are very high in developing rats. In this study, the ontogeny of hepatic isometallothioneins (MT-I and MT-II) was determined. MTs were separated and quantitated with a high-performance liquid chromatography (HPLC) method. MT-I and MT-II, first detected in fetal liver on gestation Day 18, increased coordinately during late gestation and reached maximum hepatic concentrations of approximately 400 and 500 micrograms/g, respectively, which were maintained from postpartum Days 1 through 7. Thereafter, MT concentrations decreased, reaching concentrations similar to adult levels (approximately 10 micrograms/g liver) between 28 and 35 days of age. MT-II was significantly higher than MT-I in 14- and 21-day-old rats. In 35-day-old rats, MT-I was below the detection limit. MT-I and MT-II mRNA levels were quantitated by Northern blot hybridization with mouse cRNA probes. In contrast to protein concentrations, MT mRNA reached maximal levels during late gestation which were maintained throughout the first 3 weeks postpartum. Additional experiments indicated that Cd (1-30 mumol/kg), Zn (100-3000 mumol/kg), and dexamethasone (0.3-10 mumol/kg) increased hepatic concentrations of MT-I and MT-II and their respective mRNAs in 14-day-old rats, despite the preexisting high levels of protein and mRNA at this time. These results indicate that hepatic concentrations of MT-I and MT-II isoproteins and mRNA, which increase coordinately during fetal development, decline differently during neonatal development. In 14-day-old neonates, MT-I and MT-II genes are responsive to Cd, Zn, and dexamethasone when constitutive levels of both MT mRNA and isoproteins are high.
众所周知，发育中的大鼠肝脏中金属硫蛋白（MTs）的浓度非常高。在本研究中，测定了肝脏中异金属硫蛋白（MT-I和MT-II）的个体发生情况。采用高效液相色谱（HPLC）法分离并定量MTs。MT-I和MT-II在妊娠第18天首次在胎肝中检测到，在妊娠后期协同增加，分别达到约400和500微克/克的最大肝脏浓度，并在产后第1天至第7天维持该浓度。此后，MT浓度下降，在28至35日龄之间达到与成年水平相似的浓度（约10微克/克肝脏）。在14日龄和21日龄大鼠中，MT-II显著高于MT-I。在35日龄大鼠中，MT-I低于检测限。通过与小鼠cRNA探针进行Northern印迹杂交来定量MT-I和MT-II mRNA水平。与蛋白质浓度相反，MT mRNA在妊娠后期达到最大水平，并在产后的前三周内一直维持。额外的实验表明，尽管此时MT蛋白质和mRNA已处于高水平，但镉（1 - 30微摩尔/千克）、锌（100 - 3000微摩尔/千克）和地塞米松（0.3 - 10微摩尔/千克）仍能增加14日龄大鼠肝脏中MT-I和MT-II及其各自mRNA的浓度。这些结果表明，MT-I和MT-II同工蛋白及mRNA的肝脏浓度在胎儿发育期间协同增加，而在新生儿发育期间则以不同方式下降。在14日龄的新生儿中，当MT mRNA和同工蛋白的组成水平都很高时，MT-I和MT-II基因对镉、锌和地塞米松有反应。
