Abstract
Skinned cardiac fibers exhibit SPontaneous Oscillatory Contraction (SPOC) over a broad range of intermediate activating conditions, namely, at pCa 6.0-5.0 (Ca-SPOC), or at the coexistence of MgADP and Pi under the relaxing conditions (ADP-SPOC) (Fukuda et al., 1996, 1998, 1999). We recently reported that the period of sarcomeric oscillations correlates with that of heartbeat in various animal species (Sasaki et al., 2005, 2006). We also confirmed that the period of SPOC in single cardiac myofibrils is similar to that observed in fibers (unpublished data). To further elucidate the physiological significance of SPOC, experiments need to be done with cardiomyocytes, because the excitation-contraction coupling occurs at the cellular level in vivo. The present study has therefore been undertaken to analyze SPOC in single cardiomyocytes that were enzymatically isolated from the rat ventricle. For the analysis of the waveform of sarcomeric oscillations, we used quantum dots conjugated with antibody to visualize the Z-line position in sarcomeres. We found that in skinned single myocytes the period of sarcomeric oscillations during SPOC is almost the same as that observed in fibers or myofibrils. We will report and discuss these findings at the meeting. [J Physiol Sci. 2008;58 Suppl:S66]
