REGULATION OF MICROSOMAL HEMOPROTEINS

外源性物质在肝脏中的生物转化起着重要的作用。 在人类与其化学环境的相互作用中的作用。 的 肝细胞色素P-450是一组诱导型血红素蛋白， 位于肝细胞的内质网中，作为 这种相互作用的重要生化位点。 因为金额和 细胞色素P-450的类型可能对确定 个体间对环境因子毒性作用的敏感性， 我们的实验室将继续一个正在进行的项目，以确定基本的 生物化学和分子的细节，环境因素如何诱导这些 血红素蛋白 关注P-450 p，一组独特的肝细胞色素， 大鼠和同源蛋白，兔中的LM 3c和小鼠中的MLp， 我们将定义三种已知的 这些细胞色素的诱导剂，即糖皮质激素， 抗糖皮质激素（如氰孕烯醇酮，PCN）苯巴比妥和相关 化合物和大环内酯类抗生素选择性地诱导该基因家族。 我们的方法将是分离、纯化和表征这些蛋白质 以及编码这些蛋白质的基因。 使用特异性抗体， cDNA作为分子探针，我们将确定是否转录或 转录后机制参与增加从头合成 这些蛋白质都在原代非增殖单层培养物中， 成年大鼠、兔和小鼠肝细胞，以及活体动物。 我们将 检验存在独特的“PCN受体”或“PCN”的假设 P-450 p的转录激活是一种“识别系统”， 通过确定这些基因上是否有结合位点， 典型的糖皮质激素受体 将使用现有技术 鉴定DNA酶超敏位点、受体结合位点， 作为嵌合基因克隆的P-450基因的调节元件， 转染到培养的同源肝细胞中。 最后，同样的 方法将应用于洋地黄毒苷-单洋地黄毒苷 UDP-葡萄糖醛酸转移酶，一种肝微粒体酶， 由与P-450 P系统中的操作因素类似的因素控制。 它 预计这些实验的结果将产生重要的 在理解调节的分子特异性方面的新信息 肝脏中的生物转化反应。

Biotransformation of foreign substances in the liver plays an important role in the interaction between man and his chemical environment. The liver cytochromes P-450, a group of inducible hemoproteins prominently located in the endoplasmic reticulum of the hepatocyte, serve as an important biochemical locus for this interaction. Because the amounts and types of the cytochromes P-450 may be important for determining interindividual susceptibility to toxic effects of environmental agents, our laboratory will continue an ongoing project to define the basic biochemical and molecular details of how environmental agents induce these hemoproteins. Focusing on P-450p, a unique group of liver cytochromes in the rat, and homologous proteins, LM3c in the rabbit, and MLp in the mouse, we will define the basic mechanism by which the three known classes of inducers of these cytochromes, namely, glucocorticoids and antiglutocorticoids (like cyanopregnenolone, PCN) phenobarbital and related compounds, and macrolide antibiotics selectively induce this gene family. Our approach will be to isolate, purify, and characterize these proteins and the genes which encode these proteins. Using specific antibodies and cDNAs as molecular probes, we will define whether transcriptional or post-transcriptional mechanisms are involved in increased de novo synthesis of these proteins both in primary nonproliferating monolayer cultures of adult rat, rabbit, and mouse hepatocytes, and in living animals. We will test the hypothesis that there exists a unique "PCN receptor" or "PCN recognition system" that mediates transcriptional activation of the P-450p genes by ascertaining whether there are binding sites on these genes for the classic glucocorticoid receptor. Established techniques will be used to identify DNAse hypersensitive sites, receptor binding sites, and regulatory elements of the P-450 genes cloned as chimeric genes and transvected into homologous hepatocytes in culture. Finally, the same approach will be applied to digitoxigenin-monodigitoxoside UDP-glucuronyltransferase, a liver microsomal enzyme which appears to be controlled by factors similar to those operative in the P-450p system. It is expected that the results of these experiments will produce important new information in understanding molecular specificity for regulation of biotransformation reactions in the liver.