White E, Le Guennec J Y, Nigretto J M, Gannier F, Argibay J A, Garnier D
Laboratoire d'Electrophysiologie et de Pharmacologie Cellulaires, Faculté des Sciences, Université de Tours, France.
Exp Physiol. 1993 Jan;78(1):65-78. doi: 10.1113/expphysiol.1993.sp003671.
Until recently the investigation of length-dependent effects in cardiac muscle was restricted to multicellular preparations. We describe our experimental set-up which for the first time, in single cardiac myocytes, permits the effects of changes in cell length on auxotonic contractions (measured by carbon fibre transducers) to be simultaneously recorded with the effects on membrane potential and/or changes in intracellular calcium concentration (using indo-1 AM, acetoxylmethyl form). Consistent with previous findings (in experiments at 20-25 degrees C and 0.25 Hz) we report that following a stretch there was an increase in passive tension and contraction. A stretch which increased sarcomere length by approximately 3% had no significant effect on resting membrane potential or action potential amplitude. There was, however, a significant decrease in the action potential duration (P < 0.01, n = 8). No significant change in the amplitude of the intracellular calcium transient was seen following a stretch but a reduction in its duration was observed (P < 0.025, n = 11). Our observations on intracellular calcium transients are consistent with the hypothesis that, in mechanically loaded preparations, their time course is more dependent on changes in tension than changes in length.
直到最近，对心肌长度依赖性效应的研究还局限于多细胞制剂。我们描述了我们的实验装置，它首次在单个心肌细胞中，允许同时记录细胞长度变化对辅助性收缩（通过碳纤维换能器测量）的影响以及对膜电位和/或细胞内钙浓度变化（使用indo-1 AM，乙酰氧基甲基酯形式）的影响。与先前的研究结果一致（在20-25摄氏度和0.25赫兹的实验中），我们报告称，拉伸后被动张力和收缩增加。使肌节长度增加约3%的拉伸对静息膜电位或动作电位幅度没有显著影响。然而，动作电位持续时间有显著缩短（P<0.01，n = 8）。拉伸后细胞内钙瞬变幅度没有显著变化，但观察到其持续时间缩短（P<0.025，n = 11）。我们对细胞内钙瞬变的观察结果与以下假设一致，即在机械加载的制剂中，它们的时间进程更多地取决于张力变化而非长度变化。
