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Specificity of the requirements for magnesium and calcium in the growth and metabolism of chick embryo fibroblasts
Author(s) -
Rubin H.
Publication year - 1977
Publication title -
journal of cellular physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.529
H-Index - 174
eISSN - 1097-4652
pISSN - 0021-9541
DOI - 10.1002/jcp.1040910315
Subject(s) - thymidine , embryo , intracellular , stimulation , calcium , dna synthesis , chemistry , metabolism , biophysics , biochemistry , cell growth , magnesium , dna , microbiology and biotechnology , biology , endocrinology , organic chemistry
The rate of entry of chick embryo fibroblasts (CEF) into the S‐period of the cell cycle is reduced by lowering the external supply of Mg 2+ below 0.2 mM. This slowdown, which is measured by the rate of incorporation of 3 H thymidine into DNA, can be largely reversed by doubling or tripling the concentration of Ca 2+ in the medium, normally 1.7 mM. The Ca 2+ ‐induced stimulation is shown not to depend on contaminating traces of Mg 2+ in the added Ca 2+ . The increase in cell number in the Ca 2+ ‐stimulated cultures is delayed, possibly due to cell detachment. The effect of Ca 2+ on thymidine incorporation can be simulated almost quantitatively by Sr 2+ . Ba 2+ does not produce the effect, nor do any of the other cations tested. As little as 0.2 mM Mg 2+ produces a full stimulation of thymidine incorporation in the absence of added Ca 2+ , and no substitute was found that is effective in the same concentration range. In short term experiments, i.e., 16 hours, even 5.0 mM Ca 2+ cannot stimulate thymidine incorporation to the extent achieved with 0.2 mM Mg 2+ . Large amounts of Ca 2+ or Sr 2+ can accelerate the uptake of 2‐dGlc in Mg 2+ ‐deprived cultures, but they are much less efficient than Mg 2+ in this regard also. It is suggested that Mg 2+ is the direct intracellular effector in controlling the diverse reactions of the coordinate response, and that Ca 2+ and Sr 2+ act indirectly by making Mg 2+ available to participate in these reactions.