Rich K J, Foster J R, Edwards R J, Davies D S, Boobis A R
Department of Clinical Pharmacology, Royal Postgraduate Medical School, London, United Kingdom.
J Histochem Cytochem. 1993 Jun;41(6):915-25. doi: 10.1177/41.6.8315282.
We investigated the expression, distribution, and inducibility of 3-methylcholanthrene (MC)-inducible P450 enzymes, CYP1A1 and 1A2, in livers of rabbits at different stages of development, ranging from 4 days before birth (-4 days of age) to adulthood. These enzymes were identified by immunoblotting and immunocytochemistry and quantified by dot-blotting, utilizing previously characterized monoclonal antibodies, 107 and 3/4/2, specific for CYP1A2 and both CYP1A1 and 1A2, respectively, and a polyclonal antibody that recognizes both enzymes. Expression of CYP1A2 is always greater than that of CYP1A1 in livers of untreated rabbits, regardless of age. Moreover, immunocytochemistry showed that CYP1A1 is evenly distributed throughout the liver at all ages, whereas CYP1A2 is highly localized to only a few scattered cells at 1 day before birth. More hepatocytes express this enzyme perinatally. By 6 days of age, expression of CYP1A2 is confined to a narrow band of centrilobular cells, but with increasing age the enzyme is expressed in more hepatocytes until weaning, when all hepatocytes are positive. Although CYP1A1 is induced by MC treatment at most ages, there is no change in its distribution. In contrast, induction of CYP1A2 was shown immunocytochemically to occur in only a limited number of hepatocytes in fetal rabbits. There is a progressive increase with age in the number of hepatocytes that are inducible for CYP1A2. The greatest fold-induction of hepatic CYP1A2 by MC in the rabbit is a 9-11 days of age, when, for MC-treated rabbits, CYP1A2 represents > 60% of the total P450 pool. The modulation of enzyme expression caused by MC treatment of fetuses/neonates leads to developmentally advanced livers with respect to P450 and could have a significant impact on the fetal and neonatal toxicity of some foreign compounds. These data demonstrate, for the first time, that the ontogenetic expression and localization of CYP1A1 and 1A2 within the liver are differentially regulated at the level of the individual cell.
我们研究了3-甲基胆蒽（MC）诱导型P450酶CYP1A1和1A2在不同发育阶段家兔肝脏中的表达、分布及诱导性，这些家兔的发育阶段从出生前4天（-4日龄）到成年期。利用先前鉴定的分别对CYP1A2以及CYP1A1和1A2均特异的单克隆抗体107和3/4/2，以及一种识别这两种酶的多克隆抗体，通过免疫印迹和免疫细胞化学鉴定这些酶，并通过斑点印迹进行定量。在未经处理的家兔肝脏中，无论年龄大小，CYP1A2的表达总是高于CYP1A1。此外，免疫细胞化学显示，CYP1A1在所有年龄段的肝脏中均均匀分布，而在出生前1天，CYP1A2仅高度定位于少数散在细胞中。围产期有更多肝细胞表达这种酶。到6日龄时，CYP1A2的表达局限于中央小叶细胞的一条窄带，但随着年龄增长，该酶在更多肝细胞中表达，直至断奶时所有肝细胞均呈阳性。尽管在大多数年龄段MC处理可诱导CYP1A1，但它的分布没有变化。相比之下，免疫细胞化学显示，在胎兔中，CYP1A2仅在有限数量的肝细胞中被诱导。可被CYP1A2诱导的肝细胞数量随年龄逐渐增加。在家兔中，MC对肝脏CYP1A2的最大诱导倍数出现在9 - 11日龄，此时经MC处理的家兔中，CYP1A2占总P450池的> 60%。MC处理胎儿/新生儿引起的酶表达调节导致肝脏在P450方面发育提前，并且可能对某些外来化合物的胎儿和新生儿毒性产生重大影响。这些数据首次证明，肝脏中CYP1A1和1A2的个体发生表达和定位在单个细胞水平上受到不同调节。
