The effect of calcium on the initiation and growth of human epidermal cells.

The effect of the concentration of Ca2+ in the medium on the plating efficiency of human epidermal cells has been investigated. Primary cultures plated onto lethally irradiated mouse embryo fibroblasts showed not only increased colony formation at lowered (0.2 mM) Ca2+ levels but also increased growth rate as indicated by greater colony size. On the other hand, secondary cultures showed little variation in plating efficiency and only small differences in colony size were apparent over the range 0.2-1.64 mM Ca2+. Epidermal growth factor had no effect on the Ca2+ dependence of primary or the Ca2+ independence of secondary cultures.