Effects of K+-deficiency and serum supplementation on protein turnover and nucleic acid synthesis in HeLa cells.

When most of the K+ in a chemically defined medium was replaced with Rb+, cell growth of HeLa cells was strongly inhibited. The growth was partially but significantly restored by an addition of 5% dialyzed calf serum to the medium. The inhibition of cell growth in Rb+-substituted medium was partly due to suppression of protein synthesis by K+ deficiency, but the key mechanism of inhibition is still unknown. Rb+ substitution did not influence protein degradation or nucleic acid synthesis. The restoration of cell growth on addition of serum took place chiefly through stimulation of DNA synthesis. Protein and RNA syntheses were not affected by addition of serum, and serum-induced prevention of protein degradation was less in Rb+-substituted medium than in normal K+ medium.