Ryder K O, Bryant S M, Hart G
Department of Cardiovascular Medicine, University of Oxford, John Radcliffe Hospital, Headington, U.K.
Proc Biol Sci. 1993 Jul 22;253(1336):35-42. doi: 10.1098/rspb.1993.0079.
Cell length was measured in single guinea-pig left ventricular myocytes by using a high-resolution photodiode array. Step depolarizations from a holding potential of -45 mV were applied using a switch-clamp technique with 2 M KCl microelectrodes, which were devoid of Ca2+ buffering. Comparison was made between myocytes from sham-operated guinea-pigs and guinea-pigs with mild pressure-overload left ventricular hypertrophy induced by infra-renal aortic constriction. The relation between cell shortening and membrane voltage was bell shaped, and a phasic component of shortening was evident at the range of potentials over which the L-type calcium current was activated. Mean cell shortening was increased in the hypertrophy group, and was maximal at +15 mV in both groups (control, 7.6 +/- 0.9 microns, n = 11, hypertrophy 11.0 +/- 1.2 microns, n = 20, p < 0.05). The latency to the onset of contraction was significantly shorter in the hypertrophy myocytes at -25 mV and at potentials positive to +50 mV. The relation between time-to-peak shortening and voltage showed a trend to shorter times in the hypertrophy group. At very positive potentials a slow component of contraction was identified which was relatively larger in the hypertrophy myocytes. This finding is consistent with increased calcium entry via sarcolemmal sodium-calcium exchange in the myocytes from the hypertrophy group.
使用高分辨率光电二极管阵列测量单个豚鼠左心室肌细胞的细胞长度。采用开关钳技术，使用不含Ca2+缓冲液的2M KCl微电极，从-45mV的钳制电位进行阶跃去极化。对假手术豚鼠和由肾下主动脉缩窄诱导的轻度压力超负荷左心室肥大豚鼠的肌细胞进行比较。细胞缩短与膜电压之间的关系呈钟形，在L型钙电流激活的电位范围内，缩短的相位成分明显。肥大组的平均细胞缩短增加，两组在+15mV时均达到最大值（对照组，7.6±0.9微米，n = 11，肥大组11.0±1.2微米，n = 20，p < 0.05）。在-25mV和高于+50mV的电位下，肥大肌细胞收缩开始的潜伏期明显缩短。肥大组中，缩短至峰值的时间与电压之间的关系呈缩短时间的趋势。在非常正的电位下，发现了一个缓慢的收缩成分，在肥大肌细胞中相对较大。这一发现与肥大组肌细胞中通过肌膜钠钙交换增加钙内流一致。
