Effects of Age and Cardiac Work in Vitro on Mitochondrial Oxidative Phosphorylation and (3H)-Leucine Incorporation

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Abstract
Mitochondria isolated from in vitro perfused rat heart preparations were used to study the combined effects of age and physical stress. Age-related declines in oxidative phosphorylation catalyzed by mitochondria from nonperfused hearts were not observed. Low work load perfusion resulted in decreased respiration by mitochondria from 24-month-old hearts (p < .01) but not 10-month old hearts, while high work load perfusion resulted in decreased respiration in both ages. However, the decrease by the 24-month-old hearts was significantly greater than those in the younger hearts (p < .01). Compared to age-matched low work load hearts, 5- and 10-month-old high work load hearts increased mitochondrial protein synthesis by 86% and 93%, respectively, 15-month-old hearts increased by 60%, and 24-month-old hearts by 13%. The results of this study provide evidence that the ability of the heart to respond appropriately so as to adapt to stress decreases with age, becoming apparent in the, laboratory rat between 10 and 15 months of age.

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