Effects of exercise on cardiac weight and mitochondria in male and female rats.

OSCAI, L. B., I?. A. MOLT, AND J. 0. HOLLOSZY. Efects of rwCs~ on cardiac zeeight and mitochondria in mule und female rats. Am. J. Physiol. ZO(6) : 1944-1948. 197 1 .--Female rats that swam for 6 hr daily, 6 days/week, gained wei& at the same rate as sedentary freely eatin, 0 controls. Male rats subjected to the same exercise program gained weight significantly more slowly than sedentary freely eatingcontrols. This difference is explained by the finding that the female swimmers ate significantly more than their sedentary controls while the male swimmers did not increase their food intake. The hearts of the female swimmers were significantly heavier than those of their sedentary freely eating controls. The hearts of the male swimmers were not heavier than those of their sedentary freely eating controls; however, their hearts were significantly heavier than those of sedentary paired weight animals. The exercise program had no effect on the levels of activity, expressed per gram of ventricular muscle or per milligram of protein, of cytochrome oxidase, succinate oxidase, citrate synthase, and mitochondrial malate dehydroqnase. The concentrations of cytochrome c and of mitochondrial protein, expressed per gram of ventricular muscle wcrc also unchanged.