Cardioprotective effects of exercise training on myofilament calcium activation in ovariectomized rats.
The risks associated with hormone replacement therapy, especially cardiac diseases in postmenopausal women, have prompted extensive studies for other preventive or therapeutic alternatives. We investigated the cardioprotective effects of exercise training on the changes in cardiac myofilament Ca2+ activation in 10-wk-old ovariectomized rats. The exercise groups were subjected to a 9-wk running program on a motor-driven treadmill 1 wk after surgery. The relationship between pCa (-log molar free Ca2+ concentration) and myofibrillar MgATPase activity of exercise-sham myofibrils or exercise-ovariectomized myofibrils was the same and could not be distinguished from that of sedentary-sham control hearts. In contrast, a significant suppression in maximum MgATPase activity and a leftward shift of pCa50 (half-maximally activating pCa) in the pCa-ATPase activity relationship were detected in sedentary-ovariectomized rats. Exercise training also prevented the shift in myosin heavy chain (MHC) isoforms toward beta-MHC in ovariectomized hearts. The upregulation of beta1-adrenergic receptors in the left ventricular membranes of ovariectomized rat hearts, as measured by receptor binding and immunoblot analyses, was no longer observed in exercise-ovariectomized hearts. Immunoblot analyses of heat shock protein (HSP) 72, an inducible form of HSP70, demonstrated a significant downregulation in ovariectomized hearts. Exercise training in ovariectomized rats completely reversed the expression of HSP72 to the same level as sham controls. Our results clearly indicate the cardioprotective effects of exercise training on changes in cardiac myofilament Ca2+ activation in ovariectomized rats. Alterations in expression of beta1-adrenergic receptors and HSP72 may, in part, play a mechanistic role in the cardioprotective effects.
Bupha-Intr
Tepmanas
T
Department of Physiology, Faculty of Science, Mahidol Univ., Rama 6 Rd., Bangkok 10400, Thailand.
Wattanapermpool
Jonggonnee
J
D008841:Actin Cytoskeleton / Q000378:metabolism*; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D005260:Female; D050884:HSP72 Heat-Shock Proteins; D006321:Heart / Q000502:physiology*; D006360:Heat-Shock Proteins / Q000378:metabolism; D009206:Myocardium / Q000378:metabolism*; D018995:Myosin Heavy Chains / Q000378:metabolism; D010052:Ovariectomy; D010805:Physical Conditioning, Animal / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D018342:Receptors, Adrenergic, beta-1 / Q000378:metabolism; D012420:Running / Q000502:physiology
D050884:HSP72 Heat-Shock Proteins; D006360:Heat-Shock Proteins; C000594638:MYH7 protein, rat; D018342:Receptors, Adrenergic, beta-1; D018995:Myosin Heavy Chains; D002118:Calcium