title: A mouse model with liver-specific deletion and global suppression of the NADPH-cytochrome P450 reductase gene: characterization and utility for in vivo studies of cyclophosphamide disposition.
abstract: A mouse model combining liver-specific deletion with global suppression of the NADPH-cytochrome P450 reductase gene (Cpr) has been developed and characterized. These mice (designated "Cpr-low and liver-Cpr-null" or CL-LCN) retain the respective phenotypes of the previously reported Cpr-low (CL) and liver-Cpr-null (LCN) mouse strains, but hepatic deletion of the Cpr gene occurs at an earlier age in the CL-LCN mouse than in the LCN mouse. Residual hepatic microsomal CPR activities are very low in both CL-LCN and LCN mice (at 1.5 and 2.5% of wild-type levels, respectively). The utility of CL-LCN mice for in vivo drug metabolism studies was explored using the cytochrome P450 (P450) prodrug cyclophosphamide (CPA). After i.p. injection of CPA at 100 mg/kg, the t1/2 and the area under the concentration-time curve for plasma CPA were significantly increased in mice deficient in liver CPR compared with wild-type controls, indicating a lower rate of metabolism, with the effects greater in CL-LCN mice than in LCN mice. Correspondingly, substantial decreases in Cmax, and increases in Tmax, and t1/2, of 4-hydroxycyclophosphamide (4-OH-CPA) formation were observed in both LCN and CL-LCN mice relative to wild-type controls. In contrast, CPA and 4-OH-CPA pharmacokinetic parameters were essentially unchanged in CL mice, relative to wild-type controls. The slower elimination of CPA in CL-LCN mice compared with LCN mice suggests a role for extrahepatic P450 in the in vivo metabolism of CPA and demonstrates the utility of the CL-LCN model in determining the role of extrahepatic P450 enzymes in drug metabolism and chemical toxicity.
authors.affiliation: Wadsworth Center, New York State Department of Health, Empire State Plaza, Box 509, Albany, NY 12201-0509, USA.
authors.forename: Jun
authors.initials: J
authors.lastname: Gu
authors.forename: Chong-Sheng
authors.initials: CS
authors.lastname: Chen
authors.forename: Yuan
authors.initials: Y
authors.lastname: Wei
authors.forename: Cheng
authors.initials: C
authors.lastname: Fang
authors.forename: Fang
authors.initials: F
authors.lastname: Xie
authors.forename: Kurunthachalam
authors.initials: K
authors.lastname: Kannan
authors.forename: Weizhu
authors.initials: W
authors.lastname: Yang
authors.forename: David J
authors.initials: DJ
authors.lastname: Waxman
authors.forename: Xinxin
authors.initials: X
authors.lastname: Ding
mesh_terms: D000818:Animals; D018906:Antineoplastic Agents, Alkylating / Q000097:blood / Q000493:pharmacokinetics*; D003374:Coumarins / Q000378:metabolism; D003520:Cyclophosphamide / Q000097:blood / Q000493:pharmacokinetics*; D017353:Gene Deletion; D006900:Hydroxylation; D007150:Immunohistochemistry; D008099:Liver / Q000201:enzymology*; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D008862:Microsomes, Liver / Q000378:metabolism; D009251:NADPH-Ferrihemoprotein Reductase / Q000235:genetics* / Q000502:physiology*; D014018:Tissue Distribution
chemical_list: D018906:Antineoplastic Agents, Alkylating; D003374:Coumarins; D003520:Cyclophosphamide; C030123:coumarin; D009251:NADPH-Ferrihemoprotein Reductase