title: Concentration dependent mitochondrial effect of amiodarone.
abstract: Although, the antiarrhythmic effect of amiodarone is well characterized, its effect on post-ischemic heart and cardiomyocytes, as well as the mechanism of its toxicity on extracardiac tissues is still poorly understood. In this study, we analyzed energy metabolism in situ during ischemia-reperfusion in Langendorff-perfused heart model by measuring the high-energy phosphate metabolites using 31P NMR spectroscopy. The toxicity of amiodarone on cardiomyocytes and cell lines of extracardiac origin, as well as direct effect of the drug on mitochondrial functions in isolated mitochondria was also analyzed. Amiodarone, when was present at low concentrations and predominantly in membrane bound form, protected heart and mitochondrial energy metabolism from ischemia-reperfusion-induced damages in Langendorff-perfused heart model. Toxicity of the drug was significantly higher on hepatocytes and pancreatic cells than on cardiomyocytes. In isolated mitochondria, amiodarone did not induce reactive oxygen species formation, while it affected mitochondrial permeability transition in a concentration dependent way. Up to the concentration of 10 microM, the drug considerably inhibited Ca(2+)-induced permeability transition, while at higher concentrations it induced a cyclosporin A independent permeability transition of its own. At concentrations where it inhibited the Ca(2+)-induced permeability transition (IC(50)=3.9+/-0.8 microM), it did not affect, between 6 and 30 microM it uncoupled, while, at higher concentrations it inhibited the respiratory chain. Thus, the concentration dependent nature of amiodarone's effect on permeability transition together with the different sensitivities of the tissues toward amiodarone can be involved in the beneficial cardiac and the simultaneous toxic extracardiac effects of the drug.
authors.affiliation: Institute of Biochemistry and Medical Chemistry, Medical School, University of Pecs, 12 Szigeti st., H-7624 Pecs, Hungary.
authors.forename: Gabor
authors.initials: G
authors.lastname: Varbiro
authors.forename: Ambrus
authors.initials: A
authors.lastname: Toth
authors.forename: Antal
authors.initials: A
authors.lastname: Tapodi
authors.forename: Balazs
authors.initials: B
authors.lastname: Veres
authors.forename: Balazs
authors.initials: B
authors.lastname: Sumegi
authors.forename: Ferenc
authors.initials: F
authors.lastname: Gallyas
mesh_terms: D000638:Amiodarone / Q000494:pharmacology*; D000818:Animals; D002463:Cell Membrane Permeability / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D004734:Energy Metabolism / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006321:Heart / Q000187:drug effects*; D006801:Humans; D008928:Mitochondria / Q000187:drug effects*; D009206:Myocardium / Q000166:cytology / Q000378:metabolism; D010101:Oxygen Consumption / Q000187:drug effects; D010477:Perfusion; D051381:Rats; D017208:Rats, Wistar; D017382:Reactive Oxygen Species / Q000378:metabolism; D015427:Reperfusion Injury / Q000378:metabolism; D014407:Tumor Cells, Cultured
chemical_list: D004791:Enzyme Inhibitors; D017382:Reactive Oxygen Species; D000638:Amiodarone