Effects of depletion of K+, Na+, or Ca2+ on DNA synthesis and cell cation content in chick embryo fibroblasts

✍ Scribed by David Moscatelli; Hisashi Sanui; A. Harry Rubin

• Publisher: John Wiley and Sons
• Year: 1979
• Tongue: English
• Weight: 855 KB
• Volume: 101
• Category: Article
• ISSN: 0021-9541
• DOI: 10.1002/jcp.1041010114

✦ Synopsis

Abstract

Decreasing the K^+^ concentration of the medium from 5 mM to 0.59 mM decreased the K^+^ content of chick embryo fibroblasts to 22% of control values and increased the Na^+^ content to 820% of control values. The alteration of monovalent cation content occurred within two hours but had no effect on the rate of DNA synthesis, as measured by ^3^H‐thymidine incorporation, for at least 16 hours. By decreasing the Na^+^ concentration in the medium, a 50% reduction in cellular Na^+^ could be obtained with no effect on thymidine incorporation. Since these changes in cellular Na^+^ and K^+^ are much larger than any known to occur under physiological conditions but have no effect on thymidine incorporation, we conclude that Na^+^ and K^+^ do not play a critical role in determining multiplication rate.

Addition of 1.8 mM EGTA to cells in media containing 1.7 mM Ca^2+^ and 0.8 mM Mg^2+^ inhibited thymidine incorporation and sharply decreased cellular K^+^ and increased cellular Na^+^ content. However, there was no reduction in total cellular Ca^2+^ levels. Likewise, decreasing the Ca^2+^ concentration of the medium below 0.01 mM inhibited thymidine incorporation, decreased cellular K^+^ and Mg^2+^, and increased cellular Na^+^ but did not affect total cellular Ca^2+^ levels. Inhibition of DNA synthesis, therefore, could not be correlated with changes in cellular Ca^2+^ levels.