Regional differences in effects of exercise training on contractile and biochemical properties of rat cardiac myocytes

Abstract

Myocardial function is enhanced by endurance exercise training, but the cellular mechanisms underlying this improved function remain unclear. A number of studies have shown that the characteristics of cardiac myocytes vary across the width of the ventricular wall. We have previously shown that endurance exercise training alters the Ca2+ sensitivity of tension as well as contractile protein isoform expression in rat cardiac myocytes. We tested the hypothesis that these effects of training are not uniform across the ventricular wall but are more pronounced in the subendocardial (Endo) region of the myocardium. Female Sprague-Dawley rats were divided into sedentary control (C) and exercise trained (T) groups. T rats underwent 11 wk of progressive treadmill exercise. Myocytes were isolated from the Endo region of the myocardium and from the subepicardial (Epi) region of both T and C hearts. We found an increase in the Ca2+ sensitivity of tension in T cells compared with C cells, but this difference was larger in the Endo cells than in the Epi cells. In addition, we found a training-induced increase in atrial myosin light chain 1 (aMLC1) expression that was larger in the Endo compared with Epi samples. We conclude that effects of exercise training on myocyte contractile and biochemical properties are greater in myocytes from the Endo region of the myocardium than those from the Epi region. In addition, these results provide evidence that the increase in aMLC1 expression may be responsible for some of the training-induced increase in myocyte Ca2+ sensitivity of tension.

Effects of Physical Training on the Myocardium of Female LDL Knockout Ovariectomized Mice

“…We observed that the ovariectomy associated with exercise training in wild and / or dyslipidemic mice increased cross-sectional area of cardiomyocytes (AST) and the medium nuclear volume (V), suggesting myocyte hypertrophy. Similar results 18,19 were observed in ovariectomized and trained rats, and in metabolic syndrome animals 15 subject only to physical training. The hypertrophy of the heart muscle is an attempt to heart adaptation to the overload work 11,20,21 .…”

Effect Of Resistance Training On Myocardial Contractility In Vitro After Sleep Deprivation

“…28 Another hypothesis is an impaired muscle oxygenation. [29][30][31] Besides, similarly to baseline analysis, there was an increase in the relaxation time in the PSD96.…”

“…However, data on the literature have shown that regular exercise has an impact on length-tension relationship of left ventricular cardiomyocytes, thereby increasing contraction force. [29][30][31] On the other hand, length-DT relationship was decreased in animals subjected to aerobic exercise, suggesting no effect of this type of exercise on attenuating this parameter. 25 Post-rest potentiation of electrical stimulations allows to indirectly determine the balance between the processes of Ca +2 reuptake, storage and release, controlled by sarcoplasmic reticulum, and intracellular Ca +2 release through the sarcolemma.…”

Microphthalmia Transcription Factor Isoforms in Mast Cells and the Heart

“…These accumulated data imply the importance of nucleotide sequences other than the classical E-box for transcriptional regulation by Mitf. Expression of MLC-1a causes a pronounced positive inotropic effect (39) and is associated with increased Ca 2ϩ sensitivity (6). Moreover, MLC-1a expression is augmented following myocardial infarction (25), in dilated cardiomyopathy (22), and under hemodynamic overload conditions (26).…”