Swimming training can affect intrinsic calcium current characteristics in rat myocardium

Abstract

Endurance exercise is widely assumed to improve cardiac function in humans, but the mechanisms involved in such changes are not clearly understood. The purpose of this study is to determine whether training elicits adaptations at the level of the L-type Ca(2+) channel. Sprague-Dawley rats performed swimming training at either moderate intensity (MOD) or high intensity (HIGH) during 8 weeks. The trained rats were studied by echocardiography and the whole-cell L-type Ca(2+) currents (I (Ca,L)) characteristics in a single cell were measured by standard whole-cell patch-clamp recording technique. Echocardiography showed that septal and posterior wall thickness in MOD and HIGH increased with the increased LV mass by 43 and 41%, respectively (P < 0.05). Training (P < 0.05) increased mean myocyte capacitance (approximately 38% in MOD and HIGH) and myocyte length (approximately 20% longer in MOD and 26% longer in HIGH), thus providing electrophysiological and morphological evidence that the training elicited LV cardiocyte hypertrophy. Mean peak I (Ca,L) was not different in three groups. However, whole-cell I (Ca,L) density was decreased in MOD and HIGH versus sedentary (P < 0.05), but there was no significant difference between MOD and HIGH. The present study provides the evidence of a training adaptation in intrinsic I (Ca,L) characteristics in ventricular myocardium, which demonstrates a remarkable adaptive plasticity of L-type channel characteristics in training rat heart.

Rat model of exercise-induced cardiac hypertrophy: hemodynamic characterization using left ventricular pressure-volume analysis

“…2). According to the results of echocardiography measurements, we observed significantly increased LV wall thickness and LV mass index values in exercised animals compared with controls, which is in line with previous studies (2,47). The histomorphometry of LV myocardium showed increased cardiomyocyte diameter (Fig.…”

“…finding is consistent with the features described in isolated cardiomyocytes (47,50) as well as in LV myocardium (30) derived from animals that underwent endurance training.…”

“…In contrast, other researchers reported unaltered LV end-diastolic dimensions after long-term endurance exercise training (22,47). Also, controversial data in the literature exist about LV end-systolic dimensions (2,21).…”

“…The adaptation of myocardial tissue that accompanies exercise training in experimental animal models depends on factors such as modality, intensity, duration, and frequency of the physical activity (47). According to data in the literature and results from our own previous pilot studies, we established a rat model of robust cardiac hypertrophy induced by swim training.…”

Heat acclimation and exercise training interact when combined in an overriding and trade-off manner: physiologic-genomic linkage

“…Whereas Mokelke et al (29) studying female SpragueDawley rats trained for 20 wk, found no changes in I CaL , Wang et al (39) reported unchanged I CaL but decreased I CaL density (I CaL /capacitance), apparently due to altered cardiomyocytes morphometry in rats that had undergone swimming training for 8 wk. Both reports differ from ours.…”