Radiosensitivity and biological properties of tumours. 13. Free and bound ribosome levels and protein synthesis of two tumour types, control and x-irradiated.

Abstract

SummaryTwo types of isologous mouse mammary tumour of different growth-rates (H, slow growing and G, rapidly growing) were investigated in respect to : (a) ribosomal distribution patterns, (b) endogenous protein synthesis by the use of 14C-leucine incorporation, and (c) the effect of x-irradiation on these processes.Sedimentation patterns of ribosomes of both tumour types appear similar, and their monomer peaks correspond to 73 S particles. Approximately 70 per cent of the total ribosomal population of each tumour type consists of monomers, dimers and lower oligomers. Total ribosomal population of H appears greater than that of the G tumour. The percentage of free ribosomes in G is higher than in the H tumour. Ribosomal protein and RNA levels as well as 14C-leucine incorporation are higher in the H than in the G tumour, corresponding to the higher concentration of ribosomes in the former. Maximum uptake of 14C-leucine is reached at 4 hours in the H and at 3 hours in the G tumour, 3000 R resulted in approx...