Reassociation of eukaryotic ribosomal subunits and polyamine concentration in Yoshida ascites hepatoma and Ehrlich ascites carcinoma cells during growth

: The activity on ribosome monomers of dissociation factor preparations obtained by high salt wash from ribosomes and from the post-ribosomal supernatant (cytosol) of Yoshida rat ascites hepatoma and Ehrlich mouse ascites carcinoma cells and from the liver of control and tumor-bearing animals has been determined at different periods of intraperitoneal tumor growth. The concentration of the polyamines spermine, spermidine and putrescine has also been measured under the same conditions. Results here reported show the presence of an association factor activity on subunit ribosomes at low Mg2+ concentrations in the post-ribosomal supernatant fractions of Yoshida ascites hepatoma and Ehrlich ascites carcinoma cells during tumor growth. An association factor activity also takes place in the ribosomal high salt wash extracts of Yoshida ascites cells at the terminal stages of tumor growth. Since an increase of spermidine to putrescine ratios occurs during tumor growth the changes in the rate of ribosome monomer dissociation into units here observed might be attributable, at least in part, to changes in polyamine concentrations under the conditions studied.