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K ATP channels and ‘border zone’ arrhythmias: role of the repolarization dispersion between normal and ischaemic ventricular regions
Author(s) -
Picard Sandra,
Rouet René,
Ducouret Pierre,
Puddu Paolo Emilio,
Flais Frédéric,
Criniti Anna,
Monti Francesco,
Gérard JeanLouis
Publication year - 1999
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 - 10.1038/sj.bjp.0702704
Subject(s) - glibenclamide , repolarization , medicine , electrophysiology , cardiology , border zone , channel blocker , ischemia , endocrinology , myocardial infarction , diabetes mellitus , calcium
In order to investigate the role of K ATP channel activation and repolarization dispersion on the ‘border zone’ arrhythmias induced by ischaemia‐reperfusion, the effects of glibenclamide and bimakalim, agents modifying action potential (AP) duration, were studied in an in vitro model of myocardial ‘border zone’. The electrophysiological effects of 10 μ M glibenclamide and 1 μ M bimakalim ( n =8 each), respectively K ATP channel blocker and activator, were investigated on guinea‐pig ventricular strips submitted partly to normal conditions (normal zone, NZ) and partly to simulated ischaemic then reperfused conditions (altered zone, AZ). By preventing the ischaemia‐induced AP shortening ( P <0.0001), glibenclamide reduced the dispersion of AP duration 90% (APD 90 ) between NZ and AZ ( P <0.0001), and concomitantly inhibited the ‘border zone’ arrhythmias induced by an extrastimulus (ES), their absence being significantly related to the lessened APD 90 dispersion (χ 2 =8.28, P <0.01). Bimakalim, which also reduced the APD 90 dispersion ( P <0.005) due to differential AP shortening in normal and ischaemic tissues, decreased the incidence of myocardial conduction blocks (25% of preparations versus 83% in control, n =12, P <0.05) and favoured ‘border zone’ spontaneous arrhythmias (75% of preparations versus 25% in control, P <0.05). During reperfusion, unlike bimakalim, glibenclamide inhibited the ES‐induced arrhythmias and reduced the incidence of the spontaneous ones (12% of preparations versus 92% in control, P <0.05), this latter effect being significantly related (χ 2 =6.13, P <0.02) to the lessened ischaemia‐induced AP shortening in the presence of glibenclamide ( P <0.0001). These results suggest that K ATP blockade may protect the ischaemic‐reperfused myocardium from ‘border zone’ arrhythmias concomitantly with a reduction of APD 90 dispersion between normal and ischaemic regions. Conversely, K ATP channel activation may modify the incidence of conduction blocks and exacerbate the ischaemia‐induced ‘border zone’ arrhythmias.British Journal of Pharmacology (1999) 127 , 1687–1695; doi: 10.1038/sj.bjp.0702704