title: Effect of cytochrome P-450 and flavin-containing monooxygenase modifying factors on the in vitro metabolism of amiodarone by rat and rabbit.
abstract: Experiments were conducted to affirm hepatic cytochrome P-450 involvement in the biotransformation of the class III antiarrhythmic agent, amiodarone (Am; Cordarone X) to its major metabolite, desethylamiodarone (DEA). Male Sprague-Dawley rats and male New Zealand white rabbits were treated with phenobarbital (PB) or 3-methylcholanthrene (3-MC) (to induce cytochrome P-450 (PB-inducible cytochrome(s) P-450) or P-448 (MC-inducible cytochrome P-450). In vivo decreases in rat hepatic microsomal cytochrome P-450 were achieved either by a single ip dose of CCl4 or by a 2-day treatment with CoCl2. In vitro biotransformation of Am by hepatic microsomes from PB-induced and 3-MC-induced rats and PB-induced rabbits was significantly greater than that from noninduced animals. Conversely, in vitro DEA production was significantly decreased with hepatic microsomes from CCl4- and CoCl2-pretreated rats. The classic P-450 inhibitors, piperonyl butoxide, SKF 525A, n-octylamine, and CO provided a significant reduction in the in vitro formation of DEA by microsomes from induced animals. In vitro DEA formation by hepatic microsomes from PB- and 3-MC-induced rats was significantly decreased by 0.5 mM chloroquine (specific inhibitors of PB-inducible cytochrome(s) P-450) and 0.3 mM quinacrine (specific inhibitor of MC-inducible cytochrome(s) P-450), respectively. Further evidence for involvement of gut microsomal flavin-containing monooxygenase was provided by the inhibition of gut microsomal-mediated in vitro DEA formation in the presence of methimazole. Methimazole had no effect on hepatic microsomal DEA production in vitro.(ABSTRACT TRUNCATED AT 250 WORDS)
mesh_terms: D000638:Amiodarone / Q000378:metabolism*; D000818:Animals; D003577:Cytochrome P-450 Enzyme System / Q000032:analysis / Q000502:physiology*; D066298:In Vitro Techniques; D008297:Male; D008748:Methylcholanthrene / Q000494:pharmacology; D008862:Microsomes, Liver / Q000378:metabolism; D010105:Oxygenases / Q000502:physiology*; D010634:Phenobarbital / Q000494:pharmacology; D011506:Proteins / Q000032:analysis; D011817:Rabbits; D051381:Rats; D011919:Rats, Inbred Strains
chemical_list: D011506:Proteins; D008748:Methylcholanthrene; D003577:Cytochrome P-450 Enzyme System; D010105:Oxygenases; C020066:dimethylaniline monooxygenase (N-oxide forming); D000638:Amiodarone; D010634:Phenobarbital