title: The amiodarone derivative KB130015 [2-methyl-3-(3,5-diiodo-4-carboxymethoxybenzyl)benzofuran] induces an Na+-dependent increase of [Ca2+] in ventricular myocytes.
abstract: KB130015 [KB; 2-methyl-3-(3,5-diiodo-4-carboxymethoxybenzyl)benzofuran] is a novel amiodarone derivative designed to retain the antiarrhythmic effects without the side effects. Unlike amiodarone, KB slows Na(+) current inactivation and could, via an increase in [Na(+)](i), potentially lead to Ca(2+) overload. Therefore, we studied the effects of KB on Na(+) and Ca(2+) handling in single pig ventricular myocytes using the whole-cell ruptured patch-clamp technique and K(5)fluo-3 as [Ca(2+)](i) indicator. KB at 10 microM did not prolong action potential duration but slightly increased the early plateau; spontaneous afterdepolarizations were not observed. The amplitude of the [Ca(2+)](i) transient was larger (434.9 +/- 37.2 versus 326.8 +/- 39.8 nM at baseline, n = 13, P < 0.05), and the time to peak [Ca(2+)](i) was prolonged. During voltage-clamp pulses, [Ca(2+)](i) transient peak was also larger (578.1 +/- 98.9 versus 346.4 +/- 52.6 nM at baseline, P < 0.05). Although L-type Ca(2+) current was reduced (by 21.9% at +10 mV, n = 9, P < 0.05), sarcoplasmic reticulum Ca(2+) content was significantly enhanced with KB. Forward Na(+)/Ca(2+) exchange was significantly decreased after KB application, but reverse mode of the Na(+)/Ca(2+) exchanger was significantly larger, suggesting an increase in [Na(+)](i) with KB. This was confirmed by a 2-fold increase of the [Na(+)]-dependent current generated by the Na/K-ATPase (from 0.17 +/- 0.02 to 0.38 +/- 0.06 pA/pF, P < 0.05). In conclusion, as predicted from the slowing of I(Na) inactivation, KB130015 leads to an increase in [Na(+)](i) and consequently in cellular Ca(2+) load. This effect is partially offset by a decrease in I(CaL) resulting in a mild inotropic effect without the signs of Ca(2+) overload and related arrhythmias usually associated with Na(+) channel openers.
authors.affiliation: Laboratory of Experimental Cardiology, Catholic University Leuven, Campus Gasthuisberg O/N 7th Floor, Herestraat 49, B-3000 Leuven, Belgium.
authors.forename: Virginie
authors.initials: V
authors.lastname: Bito
authors.forename: Dieter
authors.initials: D
authors.lastname: Dauwe
authors.forename: Fons
authors.initials: F
authors.lastname: Verdonck
authors.forename: Kanigula
authors.initials: K
authors.lastname: Mubagwa
authors.forename: Karin R
authors.initials: KR
authors.lastname: Sipido
mesh_terms: D000200:Action Potentials / Q000502:physiology; D000638:Amiodarone / Q000031:analogs & derivatives* / Q000494:pharmacology*; D000818:Animals; D000889:Anti-Arrhythmia Agents / Q000494:pharmacology*; D001572:Benzofurans / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism*; D002469:Cell Separation; D005260:Female; D006352:Heart Ventricles / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D066298:In Vitro Techniques; D008297:Male; D032383:Myocytes, Cardiac / Q000187:drug effects / Q000378:metabolism*; D012964:Sodium / Q000502:physiology*; D019831:Sodium-Calcium Exchanger / Q000378:metabolism; D013552:Swine
chemical_list: D000889:Anti-Arrhythmia Agents; D001572:Benzofurans; C446946:KB 130015; D019831:Sodium-Calcium Exchanger; D012964:Sodium; D000638:Amiodarone; D002118:Calcium