title: Effect of isoproterenol on local contractile behaviors of rat cardiomyocytes measured by atomic force microscopy.
abstract: 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.
authors: Graduate School of Information Science and Technology, Hokkaido University, Kita-ku N14 W9, Sapporo 060-0814, Japan. okajima@ist.hokudai.ac.jp
authors: Yusuke
authors: Y
authors: Mizutani
authors: Koichi
authors: K
authors: Kawahara
authors: Takaharu
authors: T
authors: Okajima
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D002316:Cardiotonic Agents / Q000494:pharmacology*; D002478:Cells, Cultured; D007545:Isoproterenol / Q000494:pharmacology*; D018625:Microscopy, Atomic Force; D009200:Myocardial Contraction / Q000187:drug effects; D032383:Myocytes, Cardiac / Q000187:drug effects* / Q000502:physiology; D051381:Rats; D017208:Rats, Wistar
chemical_list: D002316:Cardiotonic Agents; D007545:Isoproterenol