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Updated: Aug 8, 2026

Assessment of Myofilament Ca2+ Sensitivity Underlying Cardiac Excitation-contraction Coupling
Published on: August 1, 2016
Remodeling excitation-contraction coupling of hypertrophied ventricular myocytes is dependent on T-type calcium
Satoshi Takebayashi1, Yulong Li, Toshihiko Kaku
1Department of Cardiovascular Science, Oita University School of Medicine, Oita 879-5593, Japan.
Abstract:
We utilized Wistar rats with monocrotaline (MCT)-induced right ventricular hypertrophy (RVH) in order to evaluate the T-type Ca2+ channel current (ICaT) for myocardial contraction. RT-PCR provides that mRNA for T-type Ca2+ channel alpha1-subunits in hypertrophied myocytes was significantly higher than those in control rats (alpha1G; 264+/-36%, alpha1H; 191+/-34%; P<0.05). By whole-cell patch-clamp study, ICaT was recorded only in hypertrophied myocytes but not in control myocytes. The application of 50 nmol/L nifedipine reduced the twitch tension of the right ventricles equally in the control and RVH rats. On the other hand, 0.5 micromol/L mibefradil, a T-type Ca2+ channel blocker, strongly inhibited the twitch tension of the RVH muscle (control 6.4+/-0.8% vs. RVH 20.0+/-2.3% at 5 Hz; P<0.01). In conclusion, our results indicate the functional expression of T-type Ca2+ channels in the hypertrophied heart and their contribution to the remodeling of excitation-contraction coupling in the cardiac myocyte.
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