Miller M S, Jones A B, Chauhan D P, Park S S, Anderson L M
Perinatal Carcinogenesis Section, National Cancer Institute, Frederick, Maryland 21701-1013.
Carcinogenesis. 1989 May;10(5):875-91. doi: 10.1093/carcin/10.5.875.
Previous studies have shown that the incidences of liver and lung tumors in mice exposed transplacentally to 3-methyl-cholanthrene (MC) were significantly influenced by the sensitivity of both mothers and fetuses to induction of cytochrome(s) P-450 by polycyclic aromatic hydrocarbons. In order to delineate further the biochemical and molecular processes underlying the observed biological effects, the inductive effect of MC and beta-naphthoflavone (beta NF) on cytochrome P-450 was determined at the biochemical and molecular levels. C57BL/6 females were mated with DBA/2 males and treated i.p. on day 17 of gestation with olive oil alone, 150 mg/kg of beta NF or different doses of MC. At various times after injection the mothers were sacrificed and the fetuses removed for biochemical and molecular studies. MC caused maximal induction of aryl hydrocarbon hydroxylase (AHH) activity by 8 h in both the liver and lung. beta NF caused nearly maximal induction of AHH activity by 8 h in the lung but had little effect on liver AHH activity at this time. Maximal induction with beta NF occurred by 24 h in both organs. Addition of monoclonal antibody 1-7-1, specific for the MC-inducible forms of cytochrome P-450 (P-450IA1 and A2), to the incubation mixtures resulted in a 55-70% inhibition of AHH activity in both lung and liver assays, regardless of the inducing agent used, while having no effect on AHH activity from oil-treated mice. RNA blot analysis carried out in parallel with enzyme assays demonstrated that the levels of enzyme activity correlated very well with the levels of steady-state RNAs. MC caused maximal induction of P-450IA1 RNA levels 4 h after injection in both organs and a biphasic secondary increase was observed in the lung. Maximal levels of P-450IA1 RNA were seen at 12-16 h following injection of beta NF. However, the ratio of P-450IA1 RNAs present at 16 versus 2 h in the beta NF-treated liver appeared greater than that in the lung. P-450IA2 was also induced in fetal liver and lung, but at low levels relative to P-450IA1. The results indicate that the increase in functional AHH activity was primarily due to induction of cytochrome P-450IA1. The differences in induction kinetics observed for cytochromes P-450IA1 and A2 suggest that these enzymes exhibit both tissue- and inducer-dependent specificity.
先前的研究表明，经胎盘暴露于3-甲基胆蒽（MC）的小鼠中，肝脏和肺部肿瘤的发生率受到母体和胎儿对多环芳烃诱导细胞色素P-450敏感性的显著影响。为了进一步阐明所观察到的生物学效应背后的生化和分子过程，在生化和分子水平上测定了MC和β-萘黄酮（βNF）对细胞色素P-450的诱导作用。将C57BL/6雌性小鼠与DBA/2雄性小鼠交配，并在妊娠第17天腹腔注射单独的橄榄油、150mg/kg的βNF或不同剂量的MC。注射后不同时间处死母体，并取出胎儿进行生化和分子研究。MC在8小时时在肝脏和肺中均引起芳烃羟化酶（AHH）活性的最大诱导。βNF在8小时时在肺中引起AHH活性的近乎最大诱导，但此时对肝脏AHH活性影响很小。βNF在24小时时在两个器官中均发生最大诱导。在孵育混合物中加入对细胞色素P-450的MC诱导形式（P-450IA1和A2）具有特异性的单克隆抗体1-7-1，无论使用何种诱导剂，在肺和肝脏测定中均导致AHH活性抑制55-70%，而对经油处理小鼠的AHH活性无影响。与酶测定同时进行的RNA印迹分析表明，酶活性水平与稳态RNA水平非常相关。MC在注射后4小时在两个器官中均引起P-450IA1 RNA水平的最大诱导，并且在肺中观察到双相二次增加。注射βNF后12-16小时出现P-450IA1 RNA的最大水平。然而，在βNF处理的肝脏中，16小时与2小时时存在的P-450IA1 RNA的比率似乎大于肺中的比率。P-450IA2在胎儿肝脏和肺中也被诱导，但相对于P-450IA1水平较低。结果表明，功能性AHH活性的增加主要是由于细胞色素P-450IA1的诱导。观察到的细胞色素P-450IA1和A2诱导动力学的差异表明，这些酶表现出组织和诱导剂依赖性特异性。
