Magnesium Deprivation Reproduces the Coordinate Effects of Serum Removal or Cortisol Addition on Transport and Metabolism in Chick Embryo Fibroblasts

A variety of unrelated effectors stimulate or inhibit coordinately the same array of metabolic reactions in chick embryo fibroblasts, including the uptake of 2-deoxy-D-glucose and uridine, and the incorporation of uridine and thymidine into acid insoluble material. The coordinate inhibition of these reactions by omission of serum or addition of cortisol is reproduced quantitatively by lowering the concentration of magnesium (Mg2+) in medium containing 0.2 mM Ca2+. The response times for the utilization of uridine and thymidine following the removal of addition of Mg2+ are similar to those which follow removal or addition of serum. The effect of serum on the incorporation of choline, which is not part of the coordinate response to unrelated effectors, is not reproduced by varying Mg2+ concentrations. The results support the hypothesis that the availability of Mg2+ within the cell plays a central role in the coordinate control of transport, metabolism and growth by external physiological effectors.