Traber P G, McDonnell W M, Wang W, Florence R
Department of Internal Medicine, University of Michigan Medical School, Ann Arbor.
Biochim Biophys Acta. 1992 Dec 29;1171(2):167-75. doi: 10.1016/0167-4781(92)90117-i.
Cytochrome P-450 (P450) enzymes in the mucosa of the alimentary tract may be involved in the activation and/or inactivation of ingested xenobiotics and procarcinogens. Since the multiple P450 enzymes have overlapping substrate specificities and, in some cases, similar antigenic determinants, definitive identification of P450 genes that are expressed in various tissues requires molecular analysis. In this study, a sensitive and specific polymerase chain reaction assay along with hybridization analysis was used to examine the expression of the CYP1A gene family in the rat alimentary tract. CYP1A1 mRNA was expressed throughout the alimentary tract in untreated rats, as determined by the polymerase chain reaction. However, Northern blot analysis detected CYP1A1 mRNA and enzymatic activity only in small intestine and liver, with greater amounts in intestine. After treatment with beta-naphthoflavone, CYP1A1 mRNA and enzymatic activity was markedly induced in each alimentary tissue including esophagus, fore-stomach, glandular stomach, small intestine and colon. A single dose of inducer resulted in a rapid rise in CYP1A1 mRNA which was shown by nuclear run-on assays to be primarily due to an increase in transcription of the CYP1A1 gene. CYP1A2 mRNA was detected in significant amounts only in glandular stomach following induction although the polymerase chain reaction assay identified low levels of CYP1A2 mRNA in several other tissues. The definitive identification of the CYP1A genes that are expressed in alimentary tissue will allow the design of experiments to investigate the importance of these enzymes in the metabolism of carcinogens, and ultimately carcinogenesis, in the gastrointestinal tract. In addition, these data suggest that the aromatic hydrocarbon receptor, which mediates transcriptional induction of multiple genes by xenobiotics, is expressed through the alimentary tract.
消化道黏膜中的细胞色素P - 450（P450）酶可能参与摄入的外源性物质和前致癌物的激活和/或失活过程。由于多种P450酶具有重叠的底物特异性，并且在某些情况下具有相似的抗原决定簇，因此明确鉴定在各种组织中表达的P450基因需要进行分子分析。在本研究中，使用了一种灵敏且特异的聚合酶链反应检测方法以及杂交分析来检测大鼠消化道中CYP1A基因家族的表达。通过聚合酶链反应确定，在未处理的大鼠中，CYP1A1 mRNA在整个消化道中均有表达。然而，Northern印迹分析仅在小肠和肝脏中检测到CYP1A1 mRNA和酶活性，且在小肠中的含量更高。用β - 萘黄酮处理后，包括食管、前胃、腺胃、小肠和结肠在内的每个消化道组织中，CYP1A1 mRNA和酶活性均显著诱导。单剂量诱导剂导致CYP1A1 mRNA迅速升高，核转录分析表明这主要是由于CYP1A1基因转录增加所致。诱导后，仅在腺胃中检测到大量的CYP1A2 mRNA，尽管聚合酶链反应检测在其他几个组织中鉴定出了低水平的CYP1A2 mRNA。明确鉴定在消化道组织中表达的CYP1A基因将有助于设计实验，以研究这些酶在胃肠道致癌物代谢以及最终致癌过程中的重要性。此外，这些数据表明，介导外源性物质对多个基因转录诱导作用的芳烃受体在整个消化道中均有表达。
