Alterations in membrane Na+-Ca2+ exchange in the aging myocardium

Heart failure is a common event in the elderly. Although it is generally believed that age-induced biochemical alterations of the myocardium are directly involved in the heart failure usually encountered in the elderly, several gaps still exist in our understanding of the mechanisms involved in the contractile failure of the aged myocardium. Virtually nothing is known, for example, about the integrity of the sarcolemmal (SL) Na⁺-Ca²⁺ exchange mechanism in the aging head. In this study we have examined the status of Na⁺-Ca²⁺. exchange in SL membranes from the aging myocardium. Male Sprague Dawley rats were used and were divided into 3 groups: young (4–6 months old); middle aged (14–17 months) and old age (24–27 months). Purified SL membranes were isolated from ventricular tissues. Ca²⁺-influx of Na⁺-loaded vesicles from old hearts was depressed relative to the middle-aged group, which in turn was lower than the Ca²⁺ accumulated by vesicles from young hearts. These changes were observed at different concentrations of Ca²⁺ and at different times of incubation. The results suggest that Ca²⁺ transport by SL Na⁺-Ca²⁺ exchange mechanism is attenuated in the aging myocardium and might therefore be involved in age-induced heart failure.