Myocardial adaptations to endurance exercise in aged rats.

Isolated perfused working hearts of 25-mo-old male Sprague-Dawley rats trained to run for 16 wk were compared with hearts from 9- and 25-mo-old sedentary animals. Under low work load conditions, systolic and diastolic aortic pressures, aortic flow, and oxygen consumption of the three groups were similar. Under high work load, systolic pressure of trained old and 9-mo groups were higher than the 25-mo sedentary values, but diastolic pressures were similar. At a systolic pressure of 150 mmHg, coronary flow of the old trained heart was higher than that of the age-matched controls, although not equal to the 9-mo sedentary group. The oxygen consumption of the intact hearts under the latter conditions follows the same quantitative trend. Left ventricular cytochrome c concentrations and rates of oxidation of glutamate-malate, palmitoylcarnitine, and succinate were increased in the older rats by training but not to the level of the 9-mo old. These data indicate that appropriate exercise in aged animals improves myocardial function and aerobic energy metabolism.