The effect of an Ehrlich ascites tumour on the rate of protein synthesis in muscle and liver of the host [proceedings

Abstract

flooding of the free pools of amino acids in the tissue with phenylalanine at a specific radioactivity close to that of the injection solution. The animals were killed lOmin after the injection of isotope, and rates of protein synthesis were obtained from the specific radioactivities of phenylalanine in the protein and in the free amino acid pool of each tissue. Since the total time for synthesis and secretion of plasma proteins is at least 15min, a measurement made over lOmin in the liver includes these proteins and thus represents the full protein-synthetic activity of this organ. The results in Table 1 show that the Ehrlich Lettr6 tumour has an effect similar to that of the Walker 256 carcinoma (Sherman et al., 1950) in that the tumour-bearing animals had smaller gastrocnemius muscles and slightly larger livers than control animals of the same age. In the skeletal muscle of the tumour-bearing mice the rate of protein synthesis was 44% lower than in the controls, whereas there was an increase in protein synthesis in the liver. Thus it appears that changes in the rate of protein synthesis contribute to the effects on tissue mass. Examination of the concentrations of RNA in the tissues show similar proportional changes in response to the presence of the tumour. Since approx. 8096 of the total RNA in animal tissues is ribosomal, the results suggest that the changes in rates of protein synthesis in tissues of the tumour-bearing animals can be explained mainly in terms of alterations in the number of