Wan X, Bryant S M, Hart G
The Heart & Vascular Research Center, MetroHealth Campus, Case Western Reserve University, Cleveland, Ohio, USA.
J Anat. 2003 Jun;202(6):525-36. doi: 10.1046/j.1469-7580.2003.00187.x.
Major regional differences in the electrical properties of myocytes from ventricular muscle have been described previously, on the basis of samples taken from a maximum of three regions in each heart. In order to define the topographical basis for such differences, we studied the electrical and mechanical properties of single myocytes isolated from 20 regions throughout the ventricles in the normal guinea-pig heart. Single myocytes were isolated using an enzymatic dispersion method, and were studied under conditions that were close to physiological. Cell capacitance and action potentials were recorded using the switch-clamp technique, and cell length and evoked shortening were measured using a photodiode array system. In the left ventricular free wall, mid-myocardial cells were longer and had greater capacitative surface area than surface myocytes. There were transmural but not longitudinal differences in APD90 (action potential duration to 90% repolarization), with the longest APD90 in subendocardial and the shortest in subepicardial myocytes. We found a septum-left ventricular free wall-right ventricular free wall gradient, with the longest APD90 in the septum and the shortest in the right ventricular free wall. The regional distribution of APD90 was closely mirrored by relaxation time. Peak cell shortening was greater in subendocardial myocytes than in subepicardial myocytes in the left ventricular free wall, and in myocytes from the left side of the septum compared with the right. We concluded that the regional distribution of APD is closely and inversely related to the sequence of ventricular depolarization, and that the regional variations in cell shortening amplitude are related principally to reported regional variations in wall stress.
先前曾有研究描述过心室肌中肌细胞电特性的主要区域差异，该研究是基于从每个心脏最多三个区域采集的样本进行的。为了明确这种差异的地形学基础，我们研究了从正常豚鼠心脏心室的20个区域分离出的单个肌细胞的电特性和机械特性。使用酶分散法分离单个肌细胞，并在接近生理条件下进行研究。使用膜片钳技术记录细胞电容和动作电位，使用光电二极管阵列系统测量细胞长度和诱发的缩短。在左心室游离壁，中层心肌细胞比表层肌细胞更长，电容性表面积更大。动作电位时程90%复极化（APD90）存在跨壁差异而非纵向差异，心内膜下肌细胞的APD90最长，心外膜下肌细胞的最短。我们发现了一个从室间隔到左心室游离壁再到右心室游离壁的梯度，室间隔的APD90最长，右心室游离壁的最短。APD90的区域分布与舒张时间密切相关。在左心室游离壁，心内膜下肌细胞的峰值细胞缩短幅度大于心外膜下肌细胞，在室间隔左侧的肌细胞与右侧相比也是如此。我们得出结论，APD的区域分布与心室去极化顺序密切且呈负相关，细胞缩短幅度的区域差异主要与报道的壁应力区域差异有关。
