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Ionic mechanisms responsible for the antiarrhythmic action of dehydroevodiamine in guinea‐pig isolated cardiomyocytes
Author(s) -
Loh ShihHurng,
Lee AnRong,
Huang WenHsin,
Lin †ChengI
Publication year - 1992
Publication title -
british journal of pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.432
H-Index - 211
eISSN - 1476-5381
pISSN - 0007-1188
DOI - 10.1111/j.1476-5381.1992.tb14368.x
Subject(s) - afterdepolarization , guinea pig , sarcolemma , chemistry , myocyte , inward rectifier potassium ion channel , anti arrhythmia agents , pharmacology , biophysics , medicine , electrophysiology , repolarization , pipette , cardiac transient outward potassium current , inhibitory postsynaptic potential , voltage clamp , patch clamp , endocrinology , ion channel , biology , biochemistry , receptor , atrial fibrillation
1 Dehydroevodiamine alkaloid (DeHE), an active ingredient of a Chinese herbal medicine Wu‐Chu‐Yu ( Evodiae frutus ), has been shown to decrease aterial blood pressure in experimental animals and prolong action potential duration in cardiac cells. The aim of the present study was to explore the ionic basis of its possible antiarrhythmic effects. 2 Guinea‐pig atrial and ventricular myocytes were isolated enzymatically and the ionic currents were recorded under whole‐cell patch‐clamp with single suction pipettes. 3 DeHE at a concentration of 0.1 μ m inhibited reversibly the time‐dependent outward K current (delayed rectifier, I k ) and the Na‐dependent inward current ( I Na ). 4 In low‐K (1 m m ) and high‐Ca (9 m m ) solution, DeHE also depressed the delayed afterdepolarizations (DAD) and the transient inward current ( I ti ) induced by 2 μ m strophanthidin. On the other hand, DeHE occasionally induced early afterdepolarizations and slow response action potentials at a depolarized level. 5 At higher concentrations (1 μ m and above), the L‐type Ca current ( I Ca,L ) was moderately inhibited. 6 The present findings indicate that DeHE may depress triggered arrhythmias in Ca‐overloaded guinea‐pig cardiac myocytes through its inhibitory actions on I Na , I ti and, to a smaller extent, I Ca . DeHE may also exert class III antiarrhythmic effect through a reduction of outward K currents ( I k ) across the sarcolemma.