The effect of swimming exercise on age-dependent electrophysiological changes in female rat myocardium

Abstract

The effects of swimming exercise on age-associated electrical changes in female rat hearts were investigated. Four- and 24-month-old Wistar female rats were divided into three groups as follows: sedentary young, sedentary old and exercise old. Swimming exercise was performed for 8 weeks (60 min/day, 5 days/week). All recordings were taken from freshly isolated left ventricular myocytes of rat heart. Aging caused a significant increase in the size of myocytes; swimming exercise did not affect this change. The repolarization period of the action potential was prolonged in aged myocytes, but exercise training had no effect on this prolongation. Exercise suppressed the transient outward potassium currents, while the inactivation and reactivation kinetics did not change between the groups. Moreover, aging caused suppression in the inward rectifier potassium currents, and exercise increased this suppression. Consequently, changes in the action potential and potassium currents may contribute to the impaired cardiac function in the elderly female myocardium, and swimming exercise is not an effective strategy in reversing these electrical changes.