Changes in protein synthesis after trauma: importance of nutrition

The effect of trauma (femur fracture) on protein synthesis in rats given four different parenterally administered nutrient formulations ("diets") was investigated. Diet I was a maintenance formulation. It contained sufficient amino acids and glucose to keep the rats in nitrogen balance but was inadequate to support growth. Diet II was amino acids only, diet III was severely hypocaloric glucose, and diet IV was diet I minus the amino acids. The rats received parenterally all nutrients for the duration of the 4-5 day study. Twenty-four hours posttrauma, the fractional synthesis rates of liver, lung, heart, kidney, and muscle were estimated by infusing [15N]glycine for 17.5-19 h. (T.P. Stein, J.C. Oram-Smith, M.J. Leskiw, H.W. Wallace, L.C. Long, and J.M. Leonard. The effects of protein and calorie restriction on protein synthesis in the rat. Am. J. Physiol. 230: 1321-1326, 1976.) Two trends were found: i) on the amino acid-containing diets (I and II), most protein synthesis rates were increased posttrauma. Lung was the exception: no change was found; ii) rats on the amino acid deficient diets (III and IV) showed a decrease in the fractional muscle and lung synthesis rates posttrauma. We concluded that in this rat trauma model the requirement is mostly for amino acid nitrogen posttrauma.