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1 Department of Exercise and Sport Sciences Physiology, University of Florida, Gainesville, FL, USA; School of Medicine, Department of Sports Medicine and School of Sport Sciences and Technology, Hacettepe University, Ankara, Turkey
2 Department of Exercise and Sport Sciences Physiology, University of Florida, Gainesville, FL, USA
3 Veterans Administration and Department of Pharmacology and Therapeutics, University of Florida, Gainesville, FL, USA
4 Department of Biochemistry and Molecular Biology, University of Florida, Gainesville, FL, USA
5 Department of Exercise and Sport Sciences Physiology, University of Florida, Gainesville, FL, USA; Department of Physiology, University of Florida, Gainesville, FL, USA
* To whom correspondence should be addressed. E-mail: khamilton{at}hhp.ufl.edu.
Overexpression of heat shock protein 72 (HSP72) is associated with cardioprotection. Hyperthermia-induced HSP72 overexpression is attenuated with senescence. While exercise also increases myocardial HSP72 in young animals, it is unknown whether this effect is attenuated with aging. Therefore, we investigated the effect of aging on exercise-induced myocardial heat shock factor (HSF1) activation and HSP72 expression. Male Fischer-344 rats (6 or 24 months) were randomized to control, exercise, and hyperthermic groups. Exercise consisted of 2 days of treadmill running (60 min/day, ~75%VO2max). Hyperthermia, 15 minutes at ~41°C (colonic temperature), was achieved using a temperature-controlled heating blanket. Analyses included western blotting for myocardial HSP72 and HSF1, electromobility shifts for HSF1 activation, and northern blotting for HSP72 mRNA. Exercise and hyperthermia increased (p<0.05) myocardial HSP72 in both young (>3.5- and 2.5-fold, respectively) and aged (>3- and 1.5-fold, respectively) animals. Both exercise and hyperthermic-induction of HSP72 was attenuated with age. Myocardial HSF1 protein, HSF1 activation, and HSP72 mRNA did not differ with age. These data demonstrate that aging is associated with diminished exercise-induced myocardial HSP72 expression. Mechanisms other than HSF1 activation and transcription of HSP72 mRNA are responsible for this age-related impairment.
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