title: Dose-response relationship of cytochrome P4501b1 mRNA induction by 2,3,7,8-tetrachlorodibenzo-p-dioxin in livers of C57BL/6J and DBA/2J mice.
abstract: The dose-response relationship of cytochrome P4501b1 (Cyp1b1) and Cyp1a1 induction in livers of TCDD-treated female C57BL/6J and DBA/2J mice are described. The animals were treated i.p. with 0.001, 0.01, 0.1, 1, 10 and 50 micrograms TCDD/kg for 24 h, and Cyp1b1 and Cyp1a1 mRNA expression was analyzed by RT-PCR. In the livers of both mouse strains, the Cyp1b1 and Cyp1a1 mRNA content was increased after TCDD exposure in a dose-dependent manner. These effects were more pronounced in TCDD-responsive C57BL/6J mice than in the less responsive DBA/2J mice, although Cyp1a1 was more responsive to TCDD than Cyp1b1 in both strains. The calculated ED50 values for Cyp1b1 and Cyp1a1 induction in livers of TCDD-treated C57BL/6J mice were 1.3 and 0.08 micrograms TCDD/kg, respectively. The corresponding values for half-maximal induction response in livers of DBA/2J mice were 3.4 micrograms TCDD/kg for Cyp1b1 and 1.5 micrograms TCDD/kg for Cyp1a1. These results show that Cyp1b1 mRNA expression is less inducible by TCDD than Cyp1a1. Both genes are highly inducible in TCDD-responsive C57BL/6J mice expressing the high affinity arylhydrocarbon receptor (Ah receptor), suggesting that Cyp1b1, like Cyp1a1, is a potential Ah receptor-regulated gene.
authors.affiliation: Heinrich-Heine University of Düsseldorf, Department of Toxicology, Germany.
authors.forename: J
authors.initials: J
authors.lastname: Abel
authors.forename: W
authors.initials: W
authors.lastname: Li
authors.forename: O
authors.initials: O
authors.lastname: Döhr
authors.forename: C
authors.initials: C
authors.lastname: Vogel
authors.forename: S
authors.initials: S
authors.lastname: Donat
mesh_terms: D000818:Animals; D001189:Aryl Hydrocarbon Hydroxylases; D019363:Cytochrome P-450 CYP1A1 / Q000096:biosynthesis; D065633:Cytochrome P-450 CYP1B1; D003577:Cytochrome P-450 Enzyme System / Q000096:biosynthesis*; D004305:Dose-Response Relationship, Drug; D004790:Enzyme Induction; D005260:Female; D008099:Liver / Q000187:drug effects* / Q000201:enzymology; D051379:Mice; D008810:Mice, Inbred C57BL; D008811:Mice, Inbred DBA; D000072317:Polychlorinated Dibenzodioxins / Q000494:pharmacology*; D012333:RNA, Messenger / Q000096:biosynthesis
chemical_list: D000072317:Polychlorinated Dibenzodioxins; D012333:RNA, Messenger; D003577:Cytochrome P-450 Enzyme System; D001189:Aryl Hydrocarbon Hydroxylases; C585498:Cyp1b1 protein, mouse; D019363:Cytochrome P-450 CYP1A1; D065633:Cytochrome P-450 CYP1B1