Differential expression of stress proteins in rat myocardium after free wheel or treadmill run training

Abstract

High-intensity treadmill exercise increases the expression of a cardioprotective, inducible 72-kDa stress protein (SP72) in cardiac muscle. This investigation examined whether voluntary free wheel exercise training would be sufficient to confer a similar response. Male Sprague-Dawley rats were randomly assigned to either treadmill (TM-Tr) or free wheel (FW-Tr) training groups. By the end of the 8-wk training period, TM-Tr animals ran 1 h/day, 5 days/wk up a 10% grade, covering a distance of 8,282 m/wk. FW-Tr rats ran, on average, 5,300 m/wk, with one-third of the animals covering distances similar to those for the TM-Tr group. At the time of death, hearts of trained and caged sedentary control (Sed) animals were divided into left (LV) and right (RV) ventricles. Citrate synthase activity and the relative immunoblot contents of SP72, SP73 (the constitutive isoform of the SP70 family), and a 75-kDa mitochondrial chaperone (SP75) were subsequently determined. LV and RV did not differ on any measure, and SP73, SP75, and citrate synthase were not affected by training. Cardiac SP72 levels were elevated over fourfold in both ventricles of TM-Tr compared with RV of FW-Sed rats. Despite the animals having run a similar total distance, cardiac SP72 content in FW-Tr rats was not different from that in Sed animals. These data indicate that voluntary exercise training is insufficient to elicit an elevation of SP72 in rat heart and suggest that exercise intensity may be a critical factor in evoking the cardioprotective SP72 response.

Citrate synthase expression and enzyme activity after endurance training in cardiac and skeletal muscles

“…There is little evidence in the literature reporting that exercise training promotes an increase in CS activity in rat cardiac muscle (10). Our findings are consistent with previously published data indicating that CS activity is not altered after endurance training in rat cardiac muscle (1,2,17,18,30). It was suggested that myocardium has sufficient preexisting oxidative capacity to supply the energy requirement during exercise.…”

“…Several studies have been conducted to determine the influence of exercise training in the mitochondrial enzyme adaptation in cardiac muscles (2,10,11,18,19). Although the majority of previous studies suggest that the traininginduced alteration of mitochondrial enzymes is not noticeable in cardiac muscle (1,2,17,18,30), a few discrepant results regarding the changes were reported (10). Moreover, among the studies that have been conducted to examine the exercise-induced response of CS in cardiac muscle, very few have provided data regarding the transcriptional, translational, and/or posttranslational processes.…”

Anabolic steroid- and exercise-induced cardiac stress protein (HSP72) in the rat

“…Exercise is also a type of stressor that increases the content of HSP72 in mammalian cardiac muscle (7,8) and some evidence indicates that exerciseinduced HSP72 plays a protective role in the mammalian heart against stresses (9).…”

Adrenal peripheral clock disruption leads to altered circadian behavioral responses to voluntary exercise in middle-aged female mice

“…One may expect that wheel running, like other types of running, activates the HPA axis as well as the sympathetic nervous system (Girard & Garland 2002;Makatsori et al 2003;Naylor et al 2005;Droste et al 2006;Fediuc et al 2006;Droste et al 2007;Droste et al 2009a;Droste et al 2009b). However, the extent of activation is much lower in voluntary wheel running because it avoids the excessive stress inherent in forced treadmill running (Noble et al 1999), and mostly involves low-to-moderate resistance with higher repetition (Konhilas et al 2005). Moreover, voluntary wheel running in rodents can be differentiated from other uncontrollable stressors that inevitably involve threat or fear, as it is a predictable, controllable, and rewarding activity.…”