Combined effects of dietary restrictions and physical activity on amino acid utilization in rats.

Abstract

Female Wistar rats given protein- or energy-restricted diets or normal unrestricted diets for 1 or 7 weeks were subjected to intensive treadmill exercise. Injections of L-[U-¹⁴C]tyrosine, 21 h after the exercise, were used to trace amino acid oxidation and incorporation in tissue proteins of liver, kidneys, soleus muscle and muscles of the upper and lower foreleg. Protein restriction decreased tyrosine oxidation (expressed as percentage of the injected dose), with little effect on the incorporation in tissue proteins. Energy restriction increased tyrosine oxidation and decreased incorporation significantly. With energy restriction, amino acids are probably used to compensate for the lack of energy, resulting in a secondary protein restriction. Treadmill running, in combination with dietary protein and energy restriction, increased tyrosine incorporation in most of the tissues. The results indicate that, under dietary restriction (especially a low-energy normal-protein diet), a single bout of exercise can stimulate protein synthesis, even until 21 h after performance. On all diets the rise in tyrosine incorporation was highest for muscles of the foreleg. Recovery from muscle degeneration, resulting from exercise, might account for the increased protein synthesis. (Abstract retrieved from CAB Abstracts by CABI’s permission)