Tumor-caused changes in host protein synthesis under different dietary situations

The effect of the AC33 tumor on protein synthesis in Lewis-Wistar rats was investigated under four different dietary regimens. The four diets used were: (a) 1.25 g amino acids plus 12.5 g glucose per day, (b) 1.25 g amino acids, (c) 1.25 g glucose per day, and (d) 12.5 g glucose per day. The rats were maintained on these four diets for 4 days. On the 5th day, 65 to 75 mg 99.2% [15N] glycine were added to the infusate and infused at a constant rate for the next 18 hr. The rats were then sacrificed and the liver, lung, heart, kidney, anterior tibialis muscle, and tumor were rapidly removed and frozen in liquid nitrogen. The rate of protein synthesis for these tissues was calculated from the ratio of 15N in the tissue protein to that in the tissue intracellular fluid. The protein synthesis rates were compared with the values found for a series of nontumor control rats fed the same diets. Relative to the control rats, muscle protein synthesis decreased on Diet 1, and liver protein synthesis increased with the three deficient diets.