Comparison of the pacemaker current in canine sino-atrial node cells and the wild type mHCN2 pacemaker current in neonatal rat myocardial cells / 中华老年医学杂志

ABSTRACT

Objective To investigate the dynamic characteristics of the pacemaker current of canine sino-atrial node cells and compare them with the wild type mHCN2 pacemaker current overexpressed in neonatal rat myocardial cells.Methods Fresh canine sino-atrial node cells were enzymatically isolated in a calcium-free solution containing collagenase and elastase,and the funny current was recorded and compared with the mHCN2 current overexpressed in cultured neonatal rat myocardial cells under the same experimental conditions.Results The canine sinus node cells were elongated,spindle-shaped or polygonal,with well-defined boundaries,and showed spontaneous beating.The elicited pacemaker current was an inward current and its rise in amplitude quickened as the hyperpolarization potential increased.At V ＝-75 mV,the canine sinus atrial node pacemaker current was (-2.1±0.3) pA/pF and had the same activation kinetics as those of the mHCN2 channel current overexpressed in neonatal rat myocardial cells [τact(728±137) ms vs.(530±65) ms,P＞0.05].Conclusions Within the physiological range,the pacemaker current in canine sino-atrial node cells and the wild type mHCN2 pacemaker current over expressed in neonatal rat myocardial cells have similar activation kinetics.