Ca2+ regulatory systems in rat myocardium are altered by 24 weeks treadmill training.
The present study was conducted to investigate the effects of long-term exercise training on the main components involved in excitation-contraction coupling and relaxation in rat myocardium. Twenty male Wistar rats were divided into sedentary (S) and treadmill-trained (T) groups. Group T was trained for 24 weeks, 5 days/week (25 m/min, 45-60 min, 0% slope). 48 h after the last exercise session, animals were killed and ventricular and soleus muscle homogenates were obtained. The citrate synthase activity in soleus muscle was significantly increased (163%) in T compared with S rats ( P<0.01), confirming the exercise training efficacy. Although heart weight and cardiac oxidative capacity were not modified by exercise training, the binding of [(3)H] ryanodine and the dihydropyridine [(3)H]PN200-110 to cardiac homogenates, and sarcoplasmic reticulum Ca(2+)-ATPase activity were increased significantly in the ventricular homogenates from T compared with S animals ( P<0.01). Western blot analysis of ventricular homogenates failed to show significant alterations in dihydropyridine receptor and Ca(2+)-ATPase levels in T animals, but revealed an increase of ryanodine receptor density in this group ( P<0.01). The activity of the ectoenzymes 5'-nucleotidase and Mg(2+)-ATPase was not affected by training ( P>0.05). In conclusion, long-term treadmill training induces adaptive changes in some of the components of myocardial rat excitation-contraction coupling and relaxation systems that could contribute to the improvement of cardiac function.
Morán
María
M
Department of Biochemistry and Molecular Biology I, Faculty of Biology, Complutense University, 28040, Madrid, Spain.
Saborido
Ana
A
Megías
Alicia
A
D000818:Animals; D002118:Calcium / Q000378:metabolism; D000252:Calcium-Transporting ATPases / Q000378:metabolism*; D008297:Male; D009206:Myocardium / Q000378:metabolism*; D010805:Physical Conditioning, Animal / Q000379:methods*; D011485:Protein Binding / Q000502:physiology; D051381:Rats; D017208:Rats, Wistar; D012433:Ryanodine / Q000378:metabolism; D012519:Sarcoplasmic Reticulum / Q000378:metabolism
D012433:Ryanodine; D000252:Calcium-Transporting ATPases; D002118:Calcium