title: Pharmacokinetics of clozapine and its metabolites in hippocampal HT22 cells.
abstract: Up to now, it is not yet clear whether and how clozapine and its metabolites are metabolized in neuronal cells. The interconversion of clozapine and its metabolites, clozapine-N-oxide and norclozapine, was studied in the hippocampal neuronal in vitro system of HT22 cells. Clinically relevant concentrations of clozapine (200+400 ng/ml) and its metabolites (100+200 ng/ml) were used for the examination of the metabolizing effects after short- (4 h) and long- (24 h) term incubation. Two-way analysis of variance revealed a significant decrease of clozapine (P<0.01) and norclozapine (P<0.01) levels in the supernatants of HT22 cells after the treatment procedures. Student-Newman-Keuls tests showed a significant decrease of clozapine 400 after 24 h of incubation (P=0.01) as well as of all concentrations of norclozapine. No significant treatment effects were found for the clozapine-N-oxide degradation. Using semi-quantification by reverse transcriptase-polymerase chain reaction methods, we could show a significant increase of cytochrome P450 (CYP) 1A2 mRNA levels (P<0.05) after clozapine treatment with 200 ng/ml. The results of the present study strongly suggest that clozapine and norclozapine are metabolized in hippocampal neuronal HT22 cells by CYP1A2, whereas the levels of clozapine-N-oxide were not affected. Moreover, CYP1A2 mRNA levels were significantly changed by incubation with clozapine 200.
authors.affiliation: Department of Child and Adolescent Psychiatry and Psychotherapy, Philipps-University of Marburg, Hans-Sachs-Str 6, 35037 Marburg, Germany. heiser@mailer.uni-marburg.de
authors.forename: Philip
authors.initials: P
authors.lastname: Heiser
authors.forename: M
authors.initials: M
authors.lastname: Schüler-Springorum
authors.forename: Eva
authors.initials: E
authors.lastname: Schulte
authors.forename: Christiane
authors.initials: C
authors.lastname: Hausmann
authors.forename: Helmut
authors.initials: H
authors.lastname: Remschmidt
authors.forename: Jürgen-Christian
authors.initials: JC
authors.lastname: Krieg
authors.forename: Helmut
authors.initials: H
authors.lastname: Vedder
mesh_terms: D000704:Analysis of Variance; D001692:Biological Transport; D002478:Cells, Cultured; D003024:Clozapine / Q000031:analogs & derivatives* / Q000378:metabolism / Q000493:pharmacokinetics*; D019388:Cytochrome P-450 CYP1A2 / Q000235:genetics / Q000378:metabolism; D006624:Hippocampus / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D006801:Humans; D012333:RNA, Messenger / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: D012333:RNA, Messenger; C058272:norclozapine; D019388:Cytochrome P-450 CYP1A2; D003024:Clozapine; C079149:clozapine N-oxide