中文摘要：

本文旨在研究心肌细胞瞬时外向钾电流（transient outward potassium current，Ito）的随龄变化及其药物反应性改变。Sprague Dawley大鼠28只，分为青年组（3～5月龄）、成年组（13～15月龄）和老年组（22～24月龄）。酶法分离心室肌细胞，应用全细胞膜片钳技术记录各组Ito。并于细胞外液分别加入1．0μmol／L异丙肾上腺素,n2．0mmol／L4-氨基吡啶干预，观察Ito的变化。结果显示，与青年组和成年组相比，老年组Ito电流密度显著增加。门控动力学研究显示，老年组Ito电流稳态激活曲线左移，通道关闭态失活速率明显降低，稳态失活后恢复速率加快，而稳态失活过程无明显变化。老年组Ito对选择性抑制剂4-氨基吡啶的反应性与青年组和成年组相似，但老年组Ito对β受体激动剂异丙肾上腺素的反应性却明显弱于青年组和成年组，各组电流密度分别增加55．9％、127．5％和125．8％。上述结果提示，随着大鼠年龄的增加，心肌细胞Ito电流密度显著升高，与通道门控的激活、关闭态失活和失活后恢复机制改变有关，且老年鼠Ito对异丙肾上腺素的反应性降低。

英文摘要：

The study aimed to investigate the age-related changes and drug reactions of transient outward potassium current （Ito） of ventricular myocytes. Twenty-eight Sprague Dawley rats were divided into young （3-5 months）, adult （13-15 months） and aged （22- 24 months） groups, and/to currents of isolated myocytes from each group were recorded respectively by patch-clamp. The perfusion of 2.0 mmol/L 4-AP or 1.0 μmol/L isoproterenol was added respectively in each group, and the changes of Ito were observed. In com- parison with young and adult groups,Ito densities of ventricular myocytes in aged group was significantly increased, the curve of steady-state activation of Ito shifted to the left, the close-state inactivation rate significantly decreased, and recovery rate from the steady-state inactivation became quicker. However, no significant changes could be detected for the Ito steady-state inactivation of ventricular myocytes in aged group. The similar responsiveness to 4-AP was observed in all three groups, but the responsiveness to isoproterenol was weaker in the aged group （55.9%） than in the other two groups （127.5% and 125.8%）. In conclusion, the results show that Ito of rat ventricular myocyte of aging heart has increased current density and decreased response to isoproterenol.