title: Modulation of the expression on constitutive rat hepatic cytochrome P450 isozymes by 5-fluorouracil.
abstract: The objective of this study was to determine the effects of 5-fluorouracil (5FU) on the expression of individual cytochrome P450 (CYP) isozymes in rat liver at the catalytic activity and apoprotein levels. Male Fischer 344 rats (9 to 10) weeks old) received a single intraperitoneal injection of 5FU (120 mg/kg) or vehicle. Rats were euthanized 1, 2, 7, or 14 days following drug administration. Hepatic microsomes were isolated and used for determination of spectral CYP and heme content and steroid hydroxylation activity, and immunoblot analysis of CYP apoproteins. 5FU treatment did not alter the levels of total microsomal CYP and heme. The major male-specific CYP isozyme, CYP2C11, was downregulated by 5FU treatment, as revealed by a significant decrease in CYP2C11 immunoreactive protein and catalytic activity (progesterone 2 alpha-hydroxylase) levels at day 14. Members of the CYP3A subfamily also appeared to be modulated by 5FU treatment in a complex manner. Two days following 5FU exposure, CYP3A immunoreactive protein was increased compared with vehicle control; however, 7 days after treatment, both CYP3A immunoreactivity and catalytic activity (progesterone 6 beta-hydroxylase) were suppressed by 5FU. 5FU appears to modulate the expression of constitutive CYP isozymes in the liver of male rats. The modulation of the catalytic activity of CYP2C11 and CYP3A by 5FU appears to be due to changes in the expression of the corresponding proteins.
authors.affiliation: Department of Pharmacology, University of Toronto, ON, Canada.
authors.forename: A
authors.initials: A
authors.lastname: Afsar
authors.forename: C
authors.initials: C
authors.lastname: Lee
authors.forename: D S
authors.initials: DS
authors.lastname: Riddick
mesh_terms: D000818:Animals; D000963:Antimetabolites / Q000494:pharmacology*; D001189:Aryl Hydrocarbon Hydroxylases; D051544:Cytochrome P-450 CYP3A; D003577:Cytochrome P-450 Enzyme System / Q000032:analysis / Q000378:metabolism*; D000072467:Cytochrome P450 Family 2; D005472:Fluorouracil / Q000494:pharmacology*; D006418:Heme / Q000378:metabolism; D015151:Immunoblotting; D007527:Isoenzymes / Q000378:metabolism*; D008099:Liver / Q000187:drug effects* / Q000201:enzymology; D008297:Male; D008862:Microsomes, Liver / Q000201:enzymology; D010089:Oxidoreductases, N-Demethylating / Q000032:analysis; D051381:Rats; D011916:Rats, Inbred F344; D039181:Steroid 16-alpha-Hydroxylase; D013250:Steroid Hydroxylases / Q000032:analysis / Q000378:metabolism; D013997:Time Factors
chemical_list: D000963:Antimetabolites; D007527:Isoenzymes; D006418:Heme; D003577:Cytochrome P-450 Enzyme System; D013250:Steroid Hydroxylases; D001189:Aryl Hydrocarbon Hydroxylases; C450279:CYP2C11 protein, rat; D051544:Cytochrome P-450 CYP3A; D000072467:Cytochrome P450 Family 2; D039181:Steroid 16-alpha-Hydroxylase; D010089:Oxidoreductases, N-Demethylating; D005472:Fluorouracil