Duthinh V, Houser S R
Department of Physiology, Temple University School of Medicine, Philadelphia, Pennsylvania 19140.
Am J Physiol. 1988 Jan;254(1 Pt 2):H59-66. doi: 10.1152/ajpheart.1988.254.1.H59.
Isolated single cardiac myocytes are becoming an increasingly popular experimental preparation. To date, however, the mechanical properties of these isolated adult mammalian cardiac myocyte preparations have not been thoroughly evaluated. The aims of this research were to 1) define the basic contractile properties of externally unloaded single feline ventriculocytes, 2) determine their response to standard inotropic stimuli, and 3) determine whether contractile properties vary as a function of cell size. Cell contractions were elicited by field stimulation (1 Hz) and recorded with the use of a photodiode array technique. In the 121 myocytes studied (2 mM Ca2+; 37 degrees C) the maximum extent of shortening averaged 7.5 +/- 0.2% resting cell length (L). The maximum rates of shortening and relengthening were 92 +/- 2.7 and 103 +/- 2.0% L/s, respectively. Elevating the extracellular Ca2+ and paired pulse stimulation increased the magnitude of twitch contractions as well as the rates of shortening and relengthening. The relationship between cell size and contractile performance was assessed in this research either by comparing the contractile properties of large and small myocytes or by plotting specific contractile parameters as a function of myocyte surface area. The results of this research support the idea that single feline ventricular myocytes retain normal contractile capabilities following isolation and respond to inotropic maneuvers in a similar fashion to that observed in multicellular preparations. In addition the present experiments showed that the contractile properties of the myocytes isolated from normal feline hearts are not cell size dependent.
分离的单个心肌细胞正成为一种越来越受欢迎的实验标本。然而，迄今为止，这些分离的成年哺乳动物心肌细胞标本的力学特性尚未得到充分评估。本研究的目的是：1）确定外部无负荷的单个猫心室肌细胞的基本收缩特性；2）确定它们对标准变力刺激的反应；3）确定收缩特性是否随细胞大小而变化。通过场刺激（1赫兹）引发细胞收缩，并使用光电二极管阵列技术进行记录。在研究的121个心肌细胞中（2毫摩尔钙离子；37摄氏度），最大缩短程度平均为静息细胞长度（L）的7.5±0.2%。最大缩短速率和再延长速率分别为92±2.7和103±2.0%L/秒。升高细胞外钙离子浓度和双脉冲刺激增加了收缩期收缩的幅度以及缩短和再延长的速率。在本研究中，通过比较大、小心肌细胞的收缩特性或绘制特定收缩参数作为心肌细胞表面积的函数来评估细胞大小与收缩性能之间的关系。本研究结果支持这样一种观点，即单个猫心室肌细胞在分离后保留正常的收缩能力，并以与多细胞标本中观察到的类似方式对变力操作做出反应。此外，本实验表明，从正常猫心脏分离的心肌细胞的收缩特性不依赖于细胞大小。
