title: Down-regulation of rat hepatic microsomal cytochromes P-450 in microvesicular steatosis induced by orotic acid.
abstract: Microvesicular steatosis is an important component of the overall pathogenesis of drug-mediated liver injury. Although mitochondrial damage has a role in the development of microvesicular steatosis, the consequences of fatty change for hepatic gene function are unclear. The present study was undertaken to evaluate hepatic cytochrome P-450 (CYP) function in a rat model of microvesicular steatosis produced by the intake of diets containing 1% orotic acid (OA) that were administered for 5, 10, or 21 days. Hepatic triglyceride levels were increased to 3-fold of control after 5 days and were elevated further at 10 and 21 days. Cholesterol and phospholipid contents were increased after 10 and 21 days but not by 5 days of feeding. Microsomal androst-4-ene-3,17-dione hydroxylation activities mediated by CYP2C11 (16alpha-hydroxylation) and CYP3A2 (6beta-hydroxylation) were decreased in liver from OA-fed rats for only 5 days, whereas CYP2A1/2-mediated steroid 7alpha-hydroxylation was decreased after 10 days; these observations were complemented by immunoblot analysis that demonstrated the impaired expression of the corresponding CYP proteins. CYP2C11 mRNA, the major CYP in male rat liver, was down-regulated in steatotic liver to 52 +/- 4% of control. Thus, microvesicular steatosis induced by short-term intake of OA-containing diets is histologically similar to that produced by hepatotoxic drugs and produces the rapid down-regulation of constitutive CYPs in rat liver. Analogous processes of lipid deposition in human liver after drug- or disease-related injury could precipitate adverse effects during subsequent drug therapy.
authors.affiliation: School of Physiology and Pharmacology, University of New South Wales, Sydney, Australia.
authors.forename: G M
authors.initials: GM
authors.lastname: Su
authors.forename: R M
authors.initials: RM
authors.lastname: Sefton
authors.forename: M
authors.initials: M
authors.lastname: Murray
mesh_terms: D000735:Androstenedione / Q000378:metabolism; D000818:Animals; D001189:Aryl Hydrocarbon Hydroxylases; D001835:Body Weight; D065727:Cytochrome P-450 CYP2C8; D065729:Cytochrome P-450 CYP2C9; D051544:Cytochrome P-450 CYP3A; D003577:Cytochrome P-450 Enzyme System / Q000096:biosynthesis*; D000072467:Cytochrome P450 Family 2; D004032:Diet; D015536:Down-Regulation / Q000187:drug effects*; D005234:Fatty Liver / Q000139:chemically induced* / Q000201:enzymology*; D006900:Hydroxylation; D050356:Lipid Metabolism; D008099:Liver / Q000187:drug effects / Q000378:metabolism; D008297:Male; D008565:Membrane Proteins; D008833:Microcirculation / Q000201:enzymology / Q000473:pathology; D008862:Microsomes, Liver / Q000187:drug effects / Q000201:enzymology* / Q000648:ultrastructure; D009251:NADPH-Ferrihemoprotein Reductase / Q000378:metabolism; D015345:Oligonucleotide Probes / Q000494:pharmacology; D009963:Orotic Acid; D012333:RNA, Messenger / Q000096:biosynthesis; D051381:Rats; D017208:Rats, Wistar; D039181:Steroid 16-alpha-Hydroxylase; D013250:Steroid Hydroxylases / Q000096:biosynthesis; D013256:Steroids / Q000378:metabolism
chemical_list: D008565:Membrane Proteins; D015345:Oligonucleotide Probes; D012333:RNA, Messenger; D013256:Steroids; D000735:Androstenedione; D009963:Orotic Acid; D003577:Cytochrome P-450 Enzyme System; D013250:Steroid Hydroxylases; C450260:CYP2C9 protein, human; D065729:Cytochrome P-450 CYP2C9; D001189:Aryl Hydrocarbon Hydroxylases; C450279:CYP2C11 protein, rat; C450259:CYP2C8 protein, human; C465260:Cyp3a2 protein, rat; D065727:Cytochrome P-450 CYP2C8; D051544:Cytochrome P-450 CYP3A; D000072467:Cytochrome P450 Family 2; D039181:Steroid 16-alpha-Hydroxylase; D009251:NADPH-Ferrihemoprotein Reductase