Whole-body protein synthesis is reduced during the fed-to-fasted transition and in cases of chronic dietary restriction, however, less is known about tissue-specific alterations. We have assessed the extent to which protein synthesis in cardiac muscle responds to dietary perturbations compared to liver and skeletal muscle by applying a novel ²H₂O tracer method to quantify tissue-specific responses of protein synthesis in vivo. We hypothesized that protein synthesis in cardiac muscle is unaffected by acute fasting or food restriction, while protein synthesis in the liver and gastrocnemius muscle is reduced when there is a protein-energy deficit. We found that although protein synthesis in liver and gastrocnemius muscle were significantly reduced by acute fasting, there were no changes in protein synthesis in the left ventricle of the heart for either the total protein pool, or in isolated mitochondrial or cytosolic compartments. Likewise, a chronic reduction in calorie intake, induced by food restriction, did not affect protein synthesis in the heart whereas protein synthesis in skeletal muscle and liver were decreased. The later observations are supported by changes in the phosphorylation state of two critical mediators of protein synthesis (4E-BP1 and eIF2-) in the respective tissues. We conclude that cardiac protein synthesis is maintained in cases of nutritional perturbations, in strong contrast to liver and gastrocnemius muscle where protein synthesis is decreased by acute fasting or chronic food restriction.