Graduate School of Information Science and Technology, Hokkaido University, Kita-ku N14 W9, Sapporo 060-0814, Japan.
Curr Pharm Biotechnol. 2012 Nov;13(14):2599-603. doi: 10.2174/138920101314151120122716.
Inotropic agents induce changes in the contraction amplitude and frequency of cardiomyocytes (CMs). However, it is unknown how local contractions of CMs treated by inotropic agents behave spatiotemporally. In this study, the effect of isoproterenol, a positive inotropic agent, on local contractions of isolated neonatal rat CMs was explored by atomic force microscopy (AFM). We observed that changes in local contraction amplitude of CM in the presence of isoproterenol were heterogeneous; they were unchanged or increased, at different positions, with respect to the amplitude of untreated CMs. Interestingly, spatial heterogeneities of local contraction amplitude of CM in the presence of isoproterenol did not obviously correlate with the local elasticity, indicating that the local contractions were facilitated by cooperative dynamics of the cytoskeletal structure in relatively large regions, rather than those just under AFM indentation. Moreover, local contraction amplitude of CM in the presence of isoproterenol was not proportional to that in the control condition, showing that the former change was no longer additive in local scales.
变力药物会引起心肌细胞（CM）的收缩幅度和频率发生变化。然而，目前尚不清楚变力药物处理后的 CM 的局部收缩在时空上是如何表现的。在这项研究中，我们通过原子力显微镜（AFM）研究了拟交感神经药异丙肾上腺素对分离的新生大鼠 CM 局部收缩的影响。我们观察到，异丙肾上腺素存在时 CM 的局部收缩幅度的变化是不均匀的；相对于未处理的 CM 的幅度，CM 在不同位置的局部收缩幅度保持不变或增加。有趣的是，异丙肾上腺素存在时 CM 的局部收缩幅度的空间异质性与局部弹性没有明显的相关性，这表明局部收缩是由细胞骨架结构在相对较大区域的协同动力学促进的，而不仅仅是在 AFM 压痕下。此外，异丙肾上腺素存在时 CM 的局部收缩幅度与对照条件下的不成比例，表明前者的变化在局部尺度上不再是相加的。
