Regular swim training in a rat model induces physiological right ventricular hypertrophy and functional improvement without pathological pro-arrhythmic alterations.
BACKGROUND: Research projects have focused on exercise-induced alterations of the right ventricle (RV) of the heart, because the exercise-associated disproportionate load on the RV might lead to pathological consequences, such as interstitial fibrosis, chamber dilation or pro-arrhytmic remodelling. We aimed at providing a complex characterization of RV alterations induced by regular training in a rat model of exercise-induced cardiac remodelling. METHODS: Young, adult rats were divided into control (Co) and exercised (Ex) groups. Exercised rats swam 200 min/day for 12 weeks. In vivo cardiac electrophysiological study and in vitro force measurements on isolated permeabilized RV cardiomyocytes were performed to investigate electrical and functional alterations, respectively. Molecular biological and histological investigations were carried out. RESULTS: Ex, p < 0.05) and improved calcium sensitivity in the cardiomyocytes of exercised animals. Sarcomere protein investigations revealed marked overall and site-specific (Ser22/23, Ser43 and Thr143) hypophosphorylation of troponinI. We found prolonged QT interval (repolarization) and RV effective refracter period along with decreased gene expression of potassium channels. We could not induce any ventricular arrhythmia by programmed stimulation. CONCLUSIONS: Regular swim training induced physiological RV hypertrophy that was associated with functional improvement related to unique hypophosphorilation pattern of troponin I. A balanced exercise program without excessive exercise sessions might not be associated with induction of pathological alterations.
Oláh et al. (Tue,) studied this question.
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