Inhibition of proliferation of Ehrlich ascites carcinoma cells is functionally correlated with reduced activity of the cytosol to stimulate protein synthesis.

The cytosolic fraction prepared from in vivo stationary phase Ehrlich ascites carcinoma cells (EAC cells) stimulates in vitro protein synthesis by isolated polysomes to a substantially lower extent than the cytosol of exponentially growing cells. The cytosolic fraction of EAC cells treated in vitro for 24 h with a purified 13 kD growth inhibitor from bovine mammary gland was by 20-40% less active in stimulating in vitro protein synthesis in comparison to control cytosols. It could be shown that the growth inhibitor does not act directly on the cytosol but rather exerts its action by (a) plasma membrane mediated mechanism(s). The results are discussed with respect to correlations between regulations of cell proliferation and protein synthesis at the posttranscriptional level.