Linder M W, Prough R A
Department of Biochemistry, School of Medicine, University of Louisville, Kentucky 40292.
Arch Biochem Biophys. 1993 Apr;302(1):92-102. doi: 10.1006/abbi.1993.1185.
The expression of hepatic cytochrome P4501A1 (P4501A1), glutathione S-transferase Ya subunit (GST), and NAD(P)H:quinone oxidoreductase (QOR) proteins was evaluated in fetal, neonatal, and adolescent rats treated with 3-methylcholanthrene (MC) and the synthetic glucocorticoid dexamethasone (Dex) to elucidate the developmental aspects of glucocorticoid regulation of the induction of drug metabolizing enzymes by polycyclic aromatic hydrocarbons in vivo. These developmental states were chosen to represent either glucocorticoid deplete or replete conditions due to their differences in circulating glucocorticoid levels. Rats were treated with either MC (10 mg/kg body wt) or Dex (10 mg/kg body wt) or a combination of both and sacrificed 24 h later. In neonatal rats, the enzyme activities of P4501A1, GST, and QOR were increased by MC treatment approximately 65-, 1.4-, and 7-fold, respectively. The induction of these enzymes by MC was further potentiated an additional 2-, 1.5-, and 1.4-fold by concomitant Dex treatment. In adolescent male rats, Dex potentiated MC induction of P4501A1 activity (1.7-fold), but repressed MC induction of GST and QOR activities. When the protein contents for the three enzymes were measured by Western blot analyses, a positive correlation was observed with enzyme activities for all conditions except for the adolescent rat, where hepatic protein content of P4501A1 of rats treated with both MC and Dex was not significantly increased above the level seen with 3-methylcholanthrene treatment alone. The levels of specific mRNA and transcriptional activity for cytochrome P4501A1, GST Ya isozyme, and QOR closely paralleled the changes seen in their protein content in the livers of neonatal and adolescent rats. Dexamethasone potentiation of P4501A1 expression at the protein and RNA level were clearly statistically significant in the neonatal rat, but not in the adolescent rat, suggesting that the circulating levels of glucocorticoids are sufficiently low during the neonatal period that the full expression of induction of P4501A1 was not attained in the absence of exogenously administered glucocorticoids. These data also demonstrate that glucocorticoids have differential effects on the induction of GST Ya subunit and QOR protein and RNA in the neonatal and adolescent state, possibly related to circulating levels of glucocorticoids.
用3 - 甲基胆蒽（MC）和合成糖皮质激素地塞米松（Dex）处理胎儿、新生和青春期大鼠，以评估肝脏细胞色素P4501A1（P4501A1）、谷胱甘肽S - 转移酶Ya亚基（GST）和NAD(P)H：醌氧化还原酶（QOR）蛋白的表达，从而阐明体内多环芳烃诱导药物代谢酶过程中糖皮质激素调节的发育方面。选择这些发育阶段是因为它们循环糖皮质激素水平不同，分别代表糖皮质激素缺乏或充足的状态。大鼠分别用MC（10mg/kg体重）、Dex（10mg/kg体重）或两者联合处理，24小时后处死。在新生大鼠中，MC处理使P4501A1、GST和QOR的酶活性分别增加约65倍、1.4倍和7倍。同时给予Dex处理使MC对这些酶的诱导作用分别进一步增强2倍、1.5倍和1.4倍。在青春期雄性大鼠中，Dex增强了MC对P4501A1活性的诱导作用（1.7倍），但抑制了MC对GST和QOR活性的诱导作用。当通过蛋白质印迹分析测量这三种酶的蛋白质含量时，除青春期大鼠外，所有情况下酶活性与蛋白质含量均呈正相关，在青春期大鼠中，同时用MC和Dex处理的大鼠肝脏中P4501A1的蛋白质含量未显著高于单独用3 - 甲基胆蒽处理的水平。细胞色素P4501A1、GST Ya同工酶和QOR的特异性mRNA水平和转录活性与新生和青春期大鼠肝脏中其蛋白质含量的变化密切平行。地塞米松在蛋白质和RNA水平对P4501A1表达的增强作用在新生大鼠中具有明显的统计学意义，但在青春期大鼠中则不然，这表明新生期循环糖皮质激素水平足够低，以至于在没有外源性给予糖皮质激素的情况下，P4501A1诱导的完全表达未实现。这些数据还表明，糖皮质激素在新生期和青春期对GST Ya亚基和QOR蛋白及RNA的诱导具有不同作用，这可能与循环糖皮质激素水平有关。
