中文摘要：

目的：研究老龄大鼠心房肌细胞起搏电流（If）的特征,探讨其可能参与心房颤动的机制。方法：选择22-24月龄SD大鼠分离心房肌细胞,利用全细胞膜片钳技术记录If。结果：约85%的老龄大鼠心房肌细胞可以记录到的超极化激活If,在-150 mV时,If的电流幅值约为（382±23）pA,电流密度约为（3.2±0.4）pA/pF。而青年大鼠只有40%的心房肌细胞记录到If的电流幅值约为（86.9±8.4）pA,电流密度约为（0.9±0.1）pA/pF。从I-V曲线可见,老龄大鼠随着超极化电位的增加,电流增加幅度明显加快。在-150 mV时,其激活时间常数（τ）为（230.2±14.4）ms,而青年对照组心房肌细胞的τ则为（670.5±23.6）ms。此外,老龄大鼠心房肌细胞电流的半激活电压为（-87.2±2.3）mV,明显向更正的电位方向移动,而青年鼠细胞的半激活电压为（-104.4±6.3）mV,这使得老龄鼠的起搏电流更易激活。相反,二者的翻转电位和激活曲线斜率差异不大。结论：老龄大鼠心房肌细胞起搏电流的密度和激活均高于青年鼠。

英文摘要：

AIM：To investigate the characteristics of pacemker current（If） of atrium myocytes in aged rats.METHODS：Aged SD rats（22-24 months） were used in the study.The single atrium myocytes were isolated.If current was recorded by the technique of whole-cell patch clamp.RESULTS：The densities of If increased markedly in aged rat atrium myocytes compared with that in the cells of young rats.At the test potential of-150 mV,the average amplitude of If was（382±23）pA and the current density was（3.2±0.4）pA/pF,while the average amplitude of If in control group was（86.9±8.4）pA and the current density was（0.9±0.1）pA/pF,P〈0.01.If current was augmented at negative hyperpolarzing test potential.Time constants of activation in aged and control cells were（230.2±14.4）ms and（670.5±23.6）ms,respectively.Furthermore,steady state curves in the elder cells was shifted to positive potentials and the voltages for half maximal activation were（-87.2±2.3）mV（aged cells） and（-104.4±6.3）mV（control cells）.In contrast,the slope of activation curves and reversed potential of If were slightly different between aged cells and control cells.CONCLUSION：The amplitude and densities of If in atrium cells of aged rats were larger than that of control rats.