title: Characterization of cytochrome P2-450 (20-S) mRNA. Association with the P1-450 genomic gene and differential response to the inducers 3-methylcholanthrene and isosafrole.
abstract: Mouse liver cytochrome P2-450 is defined as the major isosafrole-inducible form of P-450 which is most specific for isosafrole metabolism. lambda AhP-1 represents a 15.5 X 10(3)-base-pair segment of mouse genomic DNA having the cytochrome P1-450 gene (approximately equal to 4600 base pairs) located in the middle portion. Using various subclones as probes, we investigated the differential expression of P1-450 mRNA and P2-450 mRNA induction as a function of association with the Ah locus, 3-methylcholanthrene or isosafrole dosage, tissue specificity, and developmental age. Both P1-450 (23-S) mRNA and P2-450 (20-S) mRNA induction processes are regulated by the Ah receptor. P2-450 mRNA is about 10-fold more sensitive than P1-450 mRNA to induction by either 3-methylcholanthrene or isosafrole. Phenobarbital pretreatment has no effect at all on either P1-450 mRNA or P2-450 mRNA. Whereas both P1-450 mRNA and P2-450 mRNA are induced by 3-methylcholanthrene in C57BL/6N liver, P1-450 (23-S) mRNA but not P2-450 (20-S) mRNA is induced by 3-methylcholanthrene in C57BL/6N kidney. P1-450 mRNA induction by 3-methylcholanthrene is measurable in C57BL/6N liver at day 15 of gestation, and the expression becomes enhanced with increasing age. P2-450 mRNA induction by 3-methylcholanthrene in C57BL/6N liver appears about 7 days later during development than 3-methylcholanthrene-inducible P1-450 mRNA. Both 3-methylcholanthrene-induced P1-450 mRNA and P2-450 mRNA are detectable in DBA/2N liver; their appearance is later in development, however, and at lower concentrations than that seen with C57BL/6N liver. P1-450 (23-S) mRNA and P2-450 (20-S) mRNA appear to hybridize to a common 5' fragment of the P1-450 gene.
mesh_terms: D000818:Animals; D003001:Cloning, Molecular; D003577:Cytochrome P-450 Enzyme System / Q000096:biosynthesis / Q000235:genetics*; D004149:Dioxoles / Q000494:pharmacology*; D004790:Enzyme Induction / Q000187:drug effects; D005260:Female; D005786:Gene Expression Regulation / Q000187:drug effects; D007668:Kidney / Q000201:enzymology; D008099:Liver / Q000201:enzymology; D008297:Male; D008748:Methylcholanthrene / Q000494:pharmacology*; D051379:Mice; D009693:Nucleic Acid Hybridization; D010634:Phenobarbital / Q000494:pharmacology; D000072317:Polychlorinated Dibenzodioxins / Q000494:pharmacology; D012333:RNA, Messenger / Q000302:isolation & purification*; D012451:Safrole / Q000494:pharmacology*
chemical_list: D004149:Dioxoles; D000072317:Polychlorinated Dibenzodioxins; D012333:RNA, Messenger; D008748:Methylcholanthrene; D003577:Cytochrome P-450 Enzyme System; D012451:Safrole; C015959:isosafrole; D010634:Phenobarbital