title: Temporal kinetics and concentration-response relationships for induction of CYP1A, CYP2B, and CYP3A in primary cultures of beagle dog hepatocytes.
abstract: Compared to other species, little information is available on the xenobiotic-induced regulation of cytochrome P450 enzymes in the beagle dog. Dogs are widely used in the pharmaceutical industry for many study types, including those that will impact decisions on compound progression. The purpose of this study was (1) to determine the temporal kinetics of drug-induced changes in canine CYP1A, CYP2B, and CYP3A mRNA and enzymatic activity, and (2) to characterize concentration-response relationships for CYP1A2, CYP2B11, and CYP3A12 using primary cultures of canine hepatocytes treated with beta-naphthoflavone (BNF), phenobarbital (PB), and rifampin (RIF), respectively. CYP1A1 and CYP1A2 mRNA exhibited maximal expression (12,700-fold and 206-fold, respectively) after 36 h of treatment with BNF. PB treatment, but not RIF treatment, caused maximal induction of CYP2B11 mRNA (149-fold) after 48 h of treatment. CYP3A12 and CYP3A26 mRNA levels were increased maximally after 72 h of treatment with PB and RIF (CYP3A12, 35-fold and 18-fold, and CYP3A26, 72-fold and 22-fold with PB and RIF treatment, respectively). Concentration-response relationships for BNF induced 7-ethoxyresorufin O-dealkylation (EROD) (EC(50) = 7.8 +/- 4.2 microM), PB induced 7-benzyloxyresorufin O-dealkylation (BROD) (EC(50) = 123 +/- 30 microM), and PB and RIF induced testosterone 6beta-hydroxylation (EC(50) = 132 +/- 28 microM and 0.98 +/- 0.16 microM) resembled the relationship for human CYP induction compared to that of rodent. Interestingly, RIF had no effect on CYP2B11 expression, which represents a species difference overlooked in previous investigations. Overall, the induction of dog CYP1A, CYP2B, and CYP3A exhibits characteristics that are intermediate to those of rodent and human.
authors.affiliation: Division of Molecular Pharmaceutics, School of Pharmacy, The University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA. richard.a.graham@gsk.com
authors.forename: Richard A
authors.initials: RA
authors.lastname: Graham
authors.forename: Lindsey O
authors.initials: LO
authors.lastname: Tyler
authors.forename: Wojciech L
authors.initials: WL
authors.lastname: Krol
authors.forename: Ivin S
authors.initials: IS
authors.lastname: Silver
authors.forename: Lindsey O
authors.initials: LO
authors.lastname: Webster
authors.forename: Philip
authors.initials: P
authors.lastname: Clark
authors.forename: Liangfu
authors.initials: L
authors.lastname: Chen
authors.forename: Troy
authors.initials: T
authors.lastname: Banks
authors.forename: Edward L
authors.initials: EL
authors.lastname: LeCluyse
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D019363:Cytochrome P-450 CYP1A1 / Q000032:analysis; D019362:Cytochrome P-450 CYP2B1 / Q000032:analysis; D051544:Cytochrome P-450 CYP3A / Q000096:biosynthesis* / Q000235:genetics; D003577:Cytochrome P-450 Enzyme System / Q000096:biosynthesis* / Q000235:genetics; D004285:Dogs; D004305:Dose-Response Relationship, Drug; D004790:Enzyme Induction / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects*; D022781:Hepatocytes / Q000187:drug effects / Q000201:enzymology*; D007700:Kinetics; D008297:Male; D010634:Phenobarbital / Q000494:pharmacology; D012333:RNA, Messenger / Q000378:metabolism; D012293:Rifampin / Q000494:pharmacology; D013045:Species Specificity; D019324:beta-Naphthoflavone / Q000494:pharmacology
chemical_list: D004791:Enzyme Inhibitors; D012333:RNA, Messenger; D019324:beta-Naphthoflavone; D003577:Cytochrome P-450 Enzyme System; D019363:Cytochrome P-450 CYP1A1; D019362:Cytochrome P-450 CYP2B1; D051544:Cytochrome P-450 CYP3A; D012293:Rifampin; D010634:Phenobarbital