PMID: 9827046Nov 25, 1998

Trimethadione metabolism and microsomal monooxygenases in untreated and phenobarbital-treated rhesus monkeys

Comparative Biochemistry and Physiology. Part C, Pharmacology, Toxicology & Endocrinology
E TanakaT Horie


The contribution of induced cytochrome P450 (P450) isozymes (CMLa; CYP2B, CMLb; CYP2A and CMLc; CYP3A) and related enzymes to trimethadione (TMO) metabolism in phenobarbital-treated rhesus monkey were investigated. The animals received a single dose of TMO (4 mg kg-1) and plasma samples were withdrawn before this administration and again at 0.08, 0.25, 0.5, 1 and 2 h later. Phenobarbital-treatment (20 mg kg-1 day-1 for 3 days; i.p.) significantly increased the plasma dimethadione (DMO)/TMO ratios at 0.08, 0.5, 1 and 2 h one's appropriate controls. Phenobarbital treatment also increased the P450 content (1.7-fold) and activity of aniline p-hydroxylase (1.3-fold), p-nitroanisole O-demethylase (1.8-fold) and benzphetamine N-demethylase (2.3-fold). The content of CMLa, CMLb and CMLc were increased about 12.8, 2.3 and 2.7-fold by phenobarbital pretreatment, respectively. The activity of TMO N-demethylation was inhibited by anti-P450 CMLa and anti-P450 CMLb. However, the anti-P450 CMLc antibody had no effect on this activity in liver microsomes. The results of both in vivo and in vitro studies of the effects of phenobarbital treatment on TMO metabolism indicate that these effects may be attributed to the induction of CMLa. These find...Continue Reading


Nov 1, 1996·Comparative Biochemistry and Physiology. Part C, Pharmacology, Toxicology & Endocrinology·E TanakaS Kobayashi


Nov 9, 2005·Food and Chemical Toxicology : an International Journal Published for the British Industrial Biological Research Association·D E AmacherMichael Mirsky
Apr 18, 2008·European Journal of Pharmacology·Johanna Fink-Gremmels

Related Concepts

Cytochrome P-450 CYP2B (lung microsomal)
P-nitroanisole O-demethylating system
Aniline Hydroxylase
Cytochrome P-450 Oxygenase
Enzyme Induction
Macaca mulatta
Microsomes, Liver

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