Immunofluorescence of Phenobarbital Inducible Cytochrome P–450 in the Hepatic Lobule of Normal and Phenobarbital–Treated Rats

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Abstract
The localization of the form of cytochrome P–450 that is induced by phenobarbital was studied by direct immunofluorescence in the hepatocytes of rats pretreated with phenobarbital in comparison with saline–treated rats. Specific fluorescence was seen in the hepatocyte cytoplasm in saline– and phenobarbital–treated rats; a more concentrated halo of fluorescence was detected surrounding the nuclei in the centrilobular zones after phenobarbital treatment. In the saline–treated rats, fluorescence was barely discernible but slightly more intense in the centrilobular than perilobular zones. In phenobarbital–treated rats, fluorescence was much more intense, with a similar but much greater difference between the centrilobular and perilobular zones. The tissue distribution and induction site of this component of the cytochrome P–450–dependent microsomal system may be relevant to the site of drug toxicity and the development of chemical carcinogenesis.