Exercise training restores ischemic preconditioning in the aging heart

OBJECTIVES To investigate the effects of ischemic preconditioning in hearts from adult and both sedentary and trained senescent rats. BACKGROUND Ischemic preconditioning does not prevent postischemic dysfuncti on in the aging heart, probably because of reduction of cardiac norepinephr ine release. Exercise training can reverse the age-related decrease of nore pinephrine production. METHODS We investigated the effects on mechanical parameters of ischemic pr econditioning against 20 min of global ischemia followed by 40 min of reper fusion in isolated perfused hearts from adult (six months) and sedentary or trained (six weeks of graduated swim training) senescent (24 months) rats. Norepinephrine release in coronary effluent was determined by highperforma nce liquid cromatography. RESULTS Final recovery of percent-developed pressure was significantly impr oved after preconditioning in adult hearts (91.6 +/- 9.6%) Versus unconditi oned controls (54.2 +/- 5.1%, p < 0.01). The effect of preconditioning on d eveloped pressure recovery was absent in sedentary but present in trained s enescent hearts (39.6 +/- 4.1% vs. 64.3 +/- 7.1%, p < 0.05). Norepinephrine release significantly increased after preconditioning in adult and in trai ned but not in sedentary senescent hearts. The depletion of myocardial nore pinephrine stores by reserpine abolished preconditioning effects in adult a nd trained senescent hearts. CONCLUSIONS In adult and trained but not in sedentary senescent hearts, pre conditioning reduces postischemic dysfunction and is associated with an inc rease in norepinephrine release. Preconditioning was blocked by reserpine i n both adult and trained senescent hearts. Thus, exercise training may rest ore preconditioning; in the senescent heart through an increase of norepine phrine release. (C) 2000 by the American College of Cardiology.