Effects of aging and long term dietary intervention on protein turnover and growth of ventricular muscle in the rat heart.

The developmental growth of the combined right and left ventricles was followed from weaning to senility in rats receiving an unrestricted diet (controls) or pair fed to one half of this food intake. The normal developmental increases in the ventricular weight, protein mass, and nucleic acid contents were retarded by this long term dietary regimen. Although the same maximum values for each variable were ultimately reached in the ventricles of the calorie restricted animals, these were achieved approximately one year later (that is, well into the extended lifespan afforded by such underfeeding). This nutritional slowing of cardiac growth was explained by a retarding of the normal developmental decline in the fractional rates of protein synthesis and protein breakdown (measured in vivo). In the control animals a net loss of ventricular protein occurred over the second year, and this might possibly be associated with a decrease in the mechanical efficiency of the aging heart. Although a similar aging atrophy was found in the ventricles of the diet restricted rats, it was delayed by a year and may be an important factor contributing to the increased longevity. This dietary intervention appears to slow the normal age related changes in cardiac protein turnover.