title: The use of transgenic cell lines for evaluating toxic metabolites of carbamazepine.
abstract: Human lymphoblastoid cell lines transgenic for human CYP450s were evaluated for the identification of toxic metabolites of the anticonvulsant drug carbamazepine (CBZ). Human CYP450 isoforms expressed by these cell lines included 1A1, 1A2, 2E1, 2A6, and 3A4. A dose-dependent inhibition of population growth from 50-200 micrograms/ml CBZ was detected by measuring cell number and respiration. The inhibition increased with the growth rate of the various lines, which correlated inversely with the presence of CYP450s, and may have been caused by CBZ itself. Cytotoxicity was observed only at the highest dose and in the line lacking transfected CYP450s. Microsomal preparations from hCYP3A4/OR cells converted CBZ into its principal oxidative metabolite, carbamazepine-10,11-epoxide (CBZ-E), at a rate of 630 pmol/min per mg protein, confirming a major role of CYP3A4 in this reaction. However, no CBZ-E (or any metabolite) was recovered from any whole-cell incubation even though hCYP3A4 cells readily converted testosterone to 6 beta-hydroxytestosterone. This suggests that differences exist between whole-cell and microsomal preparations of lymphoblastoid cells in their ability to metabolize CBZ.
authors.affiliation: Division of Genetic Toxicology, National Center for Toxicological Research, Jefferson, Arkansas, USA.
authors.forename: C R
authors.initials: CR
authors.lastname: Valentine
authors.forename: J L
authors.initials: JL
authors.lastname: Valentine
authors.forename: J
authors.initials: J
authors.lastname: Seng
authors.forename: J
authors.initials: J
authors.lastname: Leakey
authors.forename: D
authors.initials: D
authors.lastname: Casciano
mesh_terms: D001189:Aryl Hydrocarbon Hydroxylases; D002220:Carbamazepine / Q000378:metabolism / Q000633:toxicity*; D002851:Chromatography, High Pressure Liquid; D019363:Cytochrome P-450 CYP1A1 / Q000378:metabolism; D019388:Cytochrome P-450 CYP1A2 / Q000378:metabolism; D065637:Cytochrome P-450 CYP2A6; D019392:Cytochrome P-450 CYP2E1 / Q000378:metabolism; D051544:Cytochrome P-450 CYP3A; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism; D008401:Gas Chromatography-Mass Spectrometry; D006801:Humans; D008861:Microsomes / Q000187:drug effects / Q000378:metabolism; D006899:Mixed Function Oxygenases / Q000378:metabolism; D010101:Oxygen Consumption / Q000187:drug effects; D019076:Transgenes; D014407:Tumor Cells, Cultured / Q000187:drug effects / Q000201:enzymology
chemical_list: D002220:Carbamazepine; D003577:Cytochrome P-450 Enzyme System; D006899:Mixed Function Oxygenases; D019392:Cytochrome P-450 CYP2E1; D001189:Aryl Hydrocarbon Hydroxylases; C104464:CYP3A protein, human; D019363:Cytochrome P-450 CYP1A1; D019388:Cytochrome P-450 CYP1A2; D065637:Cytochrome P-450 CYP2A6; D051544:Cytochrome P-450 CYP3A; C510163:CYP3A4 protein, human