Chan H M, Cherian M G
Department of Pathology, University of Western Ontario, London, Canada.
Biochem Cell Biol. 1993 Mar-Apr;71(3-4):133-40. doi: 10.1139/o93-022.
The relative quantities of the two metallothionein isoforms (MT-1 and MT-2) in prenatal and newborn rat livers have been quantified using a competitive enzyme-linked immunosorbent assay with two specific polyclonal antisera. Both MT isoforms were detected in fetal liver on gestation day 16 and their levels continued to increase into the neonatal period. A concomitant increase was observed in plasma MT levels in the pregnant rats. The level of MT-2 was higher (75%) than that of MT-1 in the liver of both prenatal and neonatal rats. Both hepatic MT isoforms showed a significant correlation (P < 0.05) with the hepatic Zn level. Immunohistochemical localization of MT isoforms showed no apparent difference in intracellular distribution. Both MT isoforms were mainly cytoplasmic in fetal rat liver. Intense intranuclear staining was observed in newborn rat liver when the total MT concentration reached a maximum of over 1 mg MT/g tissue. The nuclear MT staining decreased with age, and at day 7, approximately equal concentrations of MT were found in nucleus and cytoplasm. When the newborn rats (1 day old) were injected with Zn (10 mg/kg), both MT isoforms were induced on days 2 and 7. Injection of Cd (1 mg/kg) increased the hepatic MT levels only on day 7. The level of MT-2 remained higher than that of MT-1 in all cases. These results suggest that both MT isoforms play a similar role in the metabolism of Zn during early development and the relative abundance of the MT isoforms may be a species-specific phenomenon.
利用竞争性酶联免疫吸附测定法及两种特异性多克隆抗血清，对产前及新生大鼠肝脏中两种金属硫蛋白亚型（MT-1和MT-2）的相对含量进行了定量分析。在妊娠第16天的胎肝中检测到了两种MT亚型，其水平在新生儿期持续升高。同时观察到怀孕大鼠血浆MT水平也有所升高。在产前及新生大鼠肝脏中，MT-2的水平均高于MT-1（75%）。两种肝脏MT亚型均与肝脏锌水平呈显著相关性（P < 0.05）。MT亚型的免疫组织化学定位显示细胞内分布无明显差异。在胎鼠肝脏中，两种MT亚型主要位于细胞质中。当总MT浓度达到最高超过1 mg MT/g组织时，在新生大鼠肝脏中观察到强烈的核内染色。核MT染色随年龄增长而减少，在第7天，细胞核和细胞质中的MT浓度大致相等。给新生大鼠（1日龄）注射锌（10 mg/kg）后，在第2天和第7天两种MT亚型均被诱导产生。注射镉（1 mg/kg）仅在第7天增加了肝脏MT水平。在所有情况下，MT-2的水平均高于MT-1。这些结果表明，在早期发育过程中，两种MT亚型在锌代谢中发挥相似作用，且MT亚型的相对丰度可能是一种物种特异性现象。
