Open AccessProtective Effect of Benidipine Against the Abnormal Electrical Activity in Single Ventricular Myocytes of the Guinea Pig Under Simulated Ischemic Conditions and Reperfusion
Author(s) -
Tomoaki Tokuno,
Katsuhiko Muraki,
Minoru Watanabe,
Yuji Imaizumi
Publication year - 2000
Publication title -
japanese journal of pharmacology/japanese journal of pharmacology
Language(s) - English
Resource type - Journals
eISSN - 1347-3506
pISSN - 0021-5198
DOI - 10.1254/jjp.82.199
Subject(s) - afterdepolarization , myocyte , dihydropyridine , ventricle , ischemia , guinea pig , glibenclamide , patch clamp , chemistry , anesthesia , medicine , cardiology , electrophysiology , biophysics , pharmacology , calcium , repolarization , endocrinology , biology , diabetes mellitus
Induction of electrical abnormalities (EAs) under simulated ischemic conditions and after reperfusion was measured from single cardiac myocytes isolated from guinea pig ventricle using whole-cell voltage or current clamp with perforated patch variation. Conditions of simulated ischemia were produced by the exchange of medium from the standard one oxygenated with 95% O2-5% CO2 gas (pH 7.4) to the modified one, which contained no glucose, 8 mM K+ and 30 mM sodium-D,L-lactate and was gassed with 90% argon-10% CO2 (pH 6.6). Under the simulated ischemia for 20 min, EAs such as delayed afterdepolarization, early afterdepolarization, automatic activity or transient inward current were observed in about 37% of myocytes driven electrically at 1 Hz. Irreversible hypercontracture occurred in myocytes of 10% or less. Upon reperfusion with the standard solution, EAs and hypercontracture were observed in about 43% and 22% of cells, respectively. Glibenclamide-sensitive current was detected during ischemia, but tended to be enhanced during reperfusion. Amplitude of Ca2+ current and ATP-sensitive K+ current after reperfusion varied widely with time and from cell to cell. When myocytes were pretreated for 10 min with 10 nM benidipine, a 1,4-dihydropyridine derivative Ca2+ blocker, the incidence of EAs and hypercontracture was markedly reduced, suggesting the protective effect of benidipine against cardiac cell injury during ischemia and reperfusion.