Stimulative effect of serum on the growth of HeLa cells suppressed in a K+-deficient chemically defined medium |
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Authors: | Tetsuhiro Sakai Toshitaka Ikehara Hiroshi Miyamoto Kenichi Kaniike |
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Affiliation: | Department of Physiology, Kinki University School of Medicine, Sayamacho, Osaka, 589 Japan |
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Abstract: | Growth of HeLa cells cultured with a chemically defined medium was slightly stimulated in the presence of 5% dialyzed calf serum. The growth-promoting action of serum was more conspicuous when cell growth was suppressed in the same medium, in which K+ was replaced by Rb+ to various ratios. The growth-promoting factors(s) of serum was heat-labile. Upon addition of dialyzed serum, passive K+ or Rb+ influx was increased, whereas the active cation uptake was unaffected and cell K+ was rather decreased. The serum did not alter uptake of [3H] amino acids. Also, protein synthesis inhibited in the Rb+-substituted medium was not stimulated significantly, except that observed only when the external K+/Rb+ ratio was . From the distinct effects of serum on cell growth and protein synthesis, we conclude that (i) the serum-induced stimulation of cell growth, which is suppressed in the Rb+-substituted medium, is not a result of the direct effect of serum on synthesis of bulk protein, but a reflection of the effect on another mechanism(s) required for cell growth; and that (ii) this action is basically identical with the growth-promoting action on cells cultured in the normal medium. |
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