title: Differential time-course and dose-response relationships of TCDD-induced CYP1B1, CYP1A1, and CYP1A2 proteins in rats.
abstract: This study examined the relationship between dose- and time-dependent hepatic localization of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and expression of CYP1B1, CYP1A1 and CYP1A2 proteins. A dose-dependent increase in hepatic TCDD in female Sprague-Dawley rats treated with 0.01-30.0 microg TCDD/kg was observed. TCDD induced CYP1A1 protein in rats treated with 0.3 microg TCDD/kg or higher. TCDD induced CYP1A2 and CYP1B1 proteins in rats treated with 1.0 microg TCDD/kg or higher. The in vivo ED50 (microg TCDD/kg) for TCDD-induced CYP1A1, CYP1A2 and CYP1B1 proteins were 0.22, 0.40 and 5.19, respectively. Hepatic accumulation of TCDD reached a maximum at 8 hours post dosing with a t1/2 of approximately 10 days. TCDD-induced CYP1A1/CYP1A2 protein expression was increased time-dependently, reaching a maximum at 3 days after dosing and remaining elevated for 35 days. In contrast, TCDD-induced CYP1B1 protein showed significant expression at 3 days after dosing and decreased to basal concentrations by 35 days. This study demonstrates that TCDD exhibits differential dose-response and time-course relationships on hepatic localization and cytochrome P-450 protein expression.
authors.affiliation: Curriculum in Toxicology, University of North Carolina, Chapel Hill 27599-7270, USA. Santostefano@herl45.herl.epa.gov
authors.forename: M J
authors.initials: MJ
authors.lastname: Santostefano
authors.forename: D G
authors.initials: DG
authors.lastname: Ross
authors.forename: U
authors.initials: U
authors.lastname: Savas
authors.forename: C R
authors.initials: CR
authors.lastname: Jefcoate
authors.forename: L S
authors.initials: LS
authors.lastname: Birnbaum
mesh_terms: D000818:Animals; D001189:Aryl Hydrocarbon Hydroxylases; D019363:Cytochrome P-450 CYP1A1 / Q000096:biosynthesis*; D019388:Cytochrome P-450 CYP1A2 / 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; D007700:Kinetics; D008862:Microsomes, Liver / Q000187:drug effects / Q000201:enzymology; D000072317:Polychlorinated Dibenzodioxins / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D000072317:Polychlorinated Dibenzodioxins; D003577:Cytochrome P-450 Enzyme System; D001189:Aryl Hydrocarbon Hydroxylases; C585499:Cyp1b1 protein, rat; D019363:Cytochrome P-450 CYP1A1; D019388:Cytochrome P-450 CYP1A2; D065633:Cytochrome P-450 CYP1B1