Submitted on November 5, 2002
Accepted on March 14, 2003
EXERCISE IMPROVES POSTISCHEMIC FUNCTION IN AGING HEART
Joseph W Starnes1*, Ryan P Taylor1, and Yoonjung Park1
1 Department of Kinesiology and Health Education, University of Texas, Austin, TX, USA
* To whom correspondence should be addressed. E-mail: jstarnes{at}mail.utexas.edu.
Exercise improves cardioprotection against ischemia-reperfusion in young animals, but has not been investigated in older animals that represent the population most likely to suffer an ischemic event. Therefore, we sought to determine the effects of aging on exercise-induced cardioprotection. Young, middle-aged, and old (4-, 12-, and 21-month-old) male F344 rats ran 60 min at 70-75% VO2max. 24h postexercise, isolated perfused working hearts underwent 22.5 min of global ischemia then 30 min of recovery (reperfusion). Compared to sedentary (n=8-9/gp), recovery of function (cardiac output x systolic pressure) improved after exercise (n=9/gp) by 40% at 4mo, 78% at 12mo, and 59% at 21mo. Exercise increased inducible heat shock protein 70 expression 105% at 4mo, but only 27% at 12mo and 24% at 21mo. Catalase activity progressively increased with age (P<0.05) and was increased by exercise at 4mo (26%) and 21mo (19%). Manganese superoxide dismutase activity was increased by exercise only at 21mo (45%). No exercise-related change in any antioxidant enzyme was observed at 12mo. We conclude that exercise can enhance cardioprotection regardless of age, but the cardioprotective protein phenotype changes with age.
