NOVEL THERAPEUTIC TARGETS FOR ANTIARRHYTHMIC DRUGS NOVEL THERAPEUTIC TARGETS FOR ANTIARRHYTHMIC DRUGS Edited by George Edward Billman Professor of Physiology andCellBiology TheOhio State University Copyright(cid:2)2010byJohnWiley&Sons,Inc.Allrightsreserved. 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Wileyalsopublishesitsbooksinavarietyofelectronicformats.Somecontentthatappearsin printmaynotbeavailableinelectronicformats.FormoreinformationaboutWileyproducts,visitour websiteatwww.wiley.com LibraryofCongressCataloging-in-PublicationData: Noveltherapeutictargetsforantiarrhythmicdrugs/[editedby]GeorgeE.Billman. p.;cm. Includesbibliographicalreferencesandindex. ISBN978-0-470-26100-2(cloth) 1. Myocardialdepressants.2. Arrhythmia–Chemotherapy. I.Billman,GeorgeE. [DNLM:1. AntiarrhythmiaAgents.2. Arrhythmias,Cardiac–drugtherapy. QV150N9372010] RM347.N682010 616.1028061–dc22 2009020796 PrintedintheUnitedStatesofAmerica 10 9 8 7 6 5 4 3 2 1 ToRosemary,friend,confidante,soulmate,andlifepartner—sempergaude. CONTENTS Acknowledgments xix Contributors xxi 1. Introduction 1 GeorgeE.Billman References 3 þ 2. Myocardial K Channels: Primary Determinants of ActionPotential Repolarization 5 NorikoNiwaandJeanneNerbonne 2.1 Introduction 5 þ 2.2 ActionPotentialWaveformsandRepolarizingK Currents 7 þ 2.3 FunctionalDiversityofRepolarizingMyocardialK Channels 9 þ 2.4 MolecularDiversityofK ChannelSubunits 12 2.5 MolecularDeterminantsofFunctionalCardiacI Channels 16 to 2.6 MolecularDeterminantsofFunctionalCardiacI Channels 18 K 2.7 MolecularDeterminantsofFunctionalCardiacKirChannels 23 2.8 OtherPotassiumCurrentsContributingtoAction PotentialRepolarization 27 þ 2.8.1 MyocardialK ChannelFunctioninginMacromolecular ProteinComplexes 28 References 32 3. The ‘‘Funny’’Pacemaker Current 59 AndreaBarbuti,AnnalisaBucchi,MirkoBaruscotti,and DarioDiFrancesco 3.1 Introduction:TheMechanismofCardiacPacemaking 59 3.2 The‘‘Funny’’Current 60 3.2.1 HistoricalBackground 60 3.2.2 BiophysicalPropertiesoftheI Current 61 f 3.2.3 AutonomicModulation 63 3.2.4 CardiacDistributionofI 63 f vii viii CONTENTS 3.3 MolecularDeterminantsoftheI Current 64 f 3.3.1 HCNClonesandPacemakerChannels 64 3.3.2 IdentificationofStructuralElementsInvolvedin ChannelGating 66 3.3.3 RegulationofPacemakerChannelActivity:“Context” DependenceandProtein-ProteinInteractions 70 3.3.4 HCNGeneRegulation 71 3.4 BlockersofFunnyChannels 72 3.4.1 Alinidine(ST567) 73 3.4.2 Falipamil(AQ-A39),Zatebradine(UL-FS49), andCilobradine(DK-AH269) 73 3.4.3 ZD7288 75 3.4.4 Ivabradine(S16257) 75 3.4.5 EffectsoftheHeartRateReducingAgentsonHCN Isoforms 78 3.5 GeneticsofHCNChannels 78 3.5.1 HCN-KOModels 78 3.5.2 PathologiesAssociatedwithHCNDysfunctions 79 3.6 HCN-BasedBiologicalPacemakers 81 References 84 4. ArrhythmiaMechanismsin Ischemia and Infarction 101 RubenCoronel,WenDun,PenelopeA.Boyden,and JacquesM.T.deBakker 4.1 Introduction 101 4.1.1 ModesofIschemia,PhasesofArrhythmogenesis 102 4.1.2 Trigger-Substrate-ModulatingFactors 103 4.2 ArrhythmogenesisinAcuteMyocardialIschemia 103 4.2.1 Phase1A 103 4.2.2 Phase1B 113 4.2.3 ArrhythmogenicMechanism:Trigger 114 4.2.4 Catecholamines 115 4.3 ArrhythmogenesisDuringtheFirstWeekPostMI 115 4.3.1 Mechanisms 115 4.3.2 TheSubendocardialPurkinjeCellasaTrigger 24–48HPostOcclusion 116 4.3.3 FiveDaysPost-Occlusion:EpicardialBorderZone 120 4.4 ArrhythmiaMechanismsinChronicInfarction 128 4.4.1 ReentryandFocalMechanisms 128 4.4.2 HeterogeneityofIonChannelExpressioninthe HealthyHeart 129 4.4.3 RemodelinginChronicMyocardialInfarction 131 4.4.4 StructuralRemodeling 133 4.4.5 RoleofthePurkinjeSystem 135 References 136
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