增龄犬左心房肌细胞动作电位和L型钙通道的变化

背景：增龄是心房颤动发生的独立危险因素，心房肌细胞电生理特性的变化是触发和维持心房颤动的重要因素。 目的：观察不同年龄犬左心房肌细胞动作电位和L型钙通道的改变。 方法：实验纳入7只成年犬和10只老年犬，用Ⅱ型胶原酶分离成年犬和老年犬的左心房肌细胞，用全细胞膜片钳方法记录成年犬和老年犬左心房肌细胞动作电位和L型钙通道电流；采用实时荧光定量PCR和Western blot检测左心房肌L型钙通道α1c亚基mRNA和蛋白的表达。 结果与结论：与成年犬相比，老年犬左心房肌细胞动作电位平台期的幅度明显降低(P < 0.05)，动作电位时程明显延长(P < 0.05)，而最大舒张电位和动作电位幅度在老年犬和成年犬间差异无显著性意义(P > 0.05)；同时老年犬左心房肌细胞的L型钙通道电流密度较成年犬明显降低(P < 0.05)，而L型钙通道电流动力学参数在成年犬和老年犬间差异无显著性意义(P > 0.05)；此外，与成年犬相比，老年犬左心房肌L型钙通道α1c亚基mRNA和蛋白的表达明显降低(P < 0.05)。由此认为，左心房肌细胞电生理学特性存在增龄性改变。

Changes of action potential and L-type calcium channel of left atrial myocytes in the aging-associated rats

BACKGROUND:Aging is the independent risk factor of atrial fibrillation. The aging-associated changes of electrophysiological properties of atrial myocytes may play an important role in the mechanisms of atrial fibrillation. OBJECTIVE:To investigate the aging-associated changes of action potential and L-type calcium channel of left atrial myocytes. METHODS:Seventeen canines were allocated to two groups, including seven adult canines and 10 old canines. The left atrial myocytes were separated from the adult and old canines by collagenase-Ⅱ. We used whole-cell patch-clamp to record action potential and L-type calcium current in left atrial myocytes of adult and older canines. The α1c subunit mRNA and protein expression of L-type calcium channel were assessed by real-time quantitative PCR and Western blotting respectively. RESULTS AND CONCLUSION:Compared with the adult canines, the amplitude of left atrial myocytes action potential plateau in old canines was significantly decreased (P < 0.05), and the action potential duration was significantly prolonged (P < 0.05), while there was no significant difference of the maximum diastolic potential and action potential amplitude (P > 0.05); the L-type calcium channel current density of the left atrial myocytes in the old canines was lower than that in the adult canines (P < 0.05), while there was no significant difference of the current kinetic parameters of L-type calcium channel between old and adult canines (P > 0.05); compared with the adult canines, the α1c subunit mRNA and protein expression of L-type calcium channel in the old canines was significantly decreased (P < 0.05). There are different aging-associated cell electrophysiological changes in the left atrial myocytes.