Abstract:

BACKGROUND: Atrial fibrillation is a common arrhythmia disease in the elderly, researches had shown that hyperpolarization activated cation current in pulmonary vein sleeve cardiomyocytes can increase the risk of arrhythmia such as atrial fibrillation.
OBJECTIVE: To study effect of isoproterenol on hyperpolarization activated cation current in pulmonary vein sleeve cardiomyocytes of elderly canine with atrial fibrillation.
METHODS: Fourteen healthy elderly canines, aged 7-9 years, were chosen, 7 canines were subjected to long-term rapidly atrial pacing (10 weeks) to induce atrial fibrillation models, and the others served as control. Dissociation of pulmonary vein sleeve yielded single cardiomyocytes by using a Landengorff column without or with pacemaker activity from long-term rapid atrial pacing canines. Pace maker current was measured with the whole-cell patch-clamp technique.
RESULT AND CONCLUSION: Isoproterenol increased the pace maker current in a concentration-dependent manner (0.1-  10.0 μmol/L). The median curative dose was 1.7 μmol/L (95% CI, 1.2-2.6 μmol/L). The isoproterenol (1.0 μmol/L) signIficantly increased pace maker current, and the current densities was increased at -120 mV test potential (P < 0.01). Isoproterenol   (10 μmol/L) caused an acceleration of current activation with V1/2 shIft to more positive potentials from mV, which approaching to rest membrane potential. Meanwhile, the slope of activated curve was changed (P < 0.01). Our study revealed that isoproterenol signIficantly promote in pulmonary vein sleeve cardiomyocytes via increasing pace maker current.