Effects of Glucose and Amino Acid Depletions on Protein Synthetic Parameters in Liver and Skeletal Muscle of Rats during Parenteral Nutrition

Abstract

Rats were nourished by intravenous infusion of four dif-ferent experimental solutions: total parenteral nutrition (TPN) solution (group I); glucose-depleted TPN solution (group II); amino acid-depleted TPN solution (group III); and glucose- and amino acid-depleted TPN solution (group IV). All except group I animals lost body weight and showed negative nitrogen balance during a 7-day experimental period; glucose-depleted groups II and IV generally suffered more severely than amino acid-depleted group III. However, the concentration of plasma albumin in group III was significantly lower than that in the other groups. The weights of liver and gastrocnemius muscles after 7 days of infusion with different nutrient compositions were fairly well correlated with the RNA/DNA ratios in these tissues. Infusion of nutritionally deficient solutions caused progressive disaggregation of polysomes in both liver and gastrocnemius muscles, indicating variable degrees of impairment of protein synthesis in these tissues. The changes in polysomal profiles were rapid and sensitive; the polysomal disaggregation was evident within one day of infusion with deficient solutions. The determination of polysomal profiles in various tissues may be useful in optimizing the composition of TPN solutions.