Late exercise training improves non-uniformity of transmural myocardial function in rats with ischaemic heart failure
| Author(s) | Younss Aït Mou, Cyril Reboul, Lucas Andre, Alain Lacampagne, Olivier Cazorla |
| Journal | Am J Physiol Lung Cell Mol Physiol, Sep 2008; 10.1152/ajplung.00053.2008 |
Method Extract | |
| isolated cardiac myocytes | |
Abstract | |
| Aims: The exercise-induced beneficial mechanisms after long-term myocardial infarction (MI) are incompletely understood. The present study evaluated the effect of treadmill exercise training (5 weeks), started at a late stage of heart failure (HF) (13 weeks post-MI), on rat left ventricle remodelling and dysfunction of the regional global and cellular contractile functions.
Methods and results: In vivo echocardiography confirmed that sub-endocardial (ENDO) layers contract more (+86%) and faster (+50%) than the sub-epicardial (EPI) layers. This gradient was lost in MI rats due to a predominant reduction in the ENDO layer contractility. Exercise partially restored the amplitude and velocity of ENDO contraction, resulting in a partial recovery of the pump function indexed by the aortic blood-flow velocity time integral. At the cellular level, MI impaired ENDO contractile properties by reducing cell shortening (10–7%), calcium transient, and myofilament Ca2+ sensitivity. These alterations were normalized by exercise. Sarcoplasmic reticulum Ca2+-ATPase (SERCA)2a expression and myosin light chain (MLC)-2 phosphorylation in ENDO cells were significantly reduced after MI and were restored by exercise. The EPI layer was only slightly reduced in vivo without cellular alterations. Conclusion: This study shows that exercise performed at a late stage after MI restored a transmural non-uniformity of myocardium lost during HF. Recoveries of Ca2+ homeostasis and myofilament function of cardiomyocytes contribute to this beneficial effect.
KEYWORDS End-stage heart failure; Myocardial contractility; Contraction; Exercise; Myocardial infarction | |
| Keywords | calcium, fura, skinned, permeabilized, force, sarcomere length |