Changes in protein turnover during gestation in the foetuses,placentas, liver,muscle and whole body of rats given a low-protein diet

(1)Protein synthesis and content have been studied in skeletal muscle, liver, foetuses and placentas of pregnant rats given a protein-deficient diet. Changes which occurred during the anabolic and subsequent catabolic phases of pregnancy are compared with those in well-fed pregnant and in protein-deficient non-pregnant rats. (2) The normal increase in liver protein did not occur during pregnancy in the protein-deficient group. (3) Protein deficiency affected protein content of the placenta earlier and more severely than that of the foetus. (4) Rates of protein synthesis in liver, placentas and foetuses were enhanced above control values by protein deficiency. (5)_Muscle protein increased normally during the anabolic phase of pregnancy but fell during the catabolic phase, unlike values for weel-fed animals. (6) Muscle protein synthesis rates rose by similar amounts in well-fed and protein-deficient animals during the anabolic phase of pregnancy. The fall to starting values during the catabolic phase was sharper and earlier in protein-deficient animals, which could reduce demands on the body amino acid pool by an amount equivalent to over 50% of the needs for protein deposition in foetuses and placentas. Thus, changes in muscle protein synthesis in both anabolic and catabolic phases of pregnancy may afford some protection to foetal protein synthesis.