ELECTROPHYSIOLOGICAL PROPERTIES OF THE LA-PV TISSUES OF Xjn-GENE KNOCKOUT MICE

摘要

It is well documented that pulmonary vein (PV) cardiomyocytes have distinct action potentials (APs) and ionic profiles. The aims of present study were to characterize electrophysiological features of murine left atrium-PV preparations obtained from Xin gene-knockout mice (developed by Professor Jim Lin, University of Iowa, USA), which characteristically have defects in intercalated disc and gap junctions of cardiac cells. Around 55 % of LA-PVs were active spontaneously at 37 (deg)C. The remaining LA-PVs were driven at 3-6 Hz. Early (EAD) and delayed afterdepolarization (DAD) could be induced by 3 types of challengers (exposure to ACh, or isoproterenol or high [Ca]_o-low [K]_0 solution) in part of wild-type mice and also in Xin gene-KO mice as well. EADs were followed by episode of high-frequency (>18 Hz) atrial fibrillation in 3 of 11 wild-type preparations but none in Xin gene-KO preparations. In ventricular myocytes isolated enzymatically from Xin gene-KO mice, the expression of transient outward currents were significantly depressed, along with a prolonged AP duration. It is suggested that defective intercalated disc and longer refractory period in Xin gene-KO LA-PV myocytes might block the onset of reentrant tachyarrhythmias in these preparations.