Effect of Calcium and Magnesium on the Morphology and Growth Pattern of L-M Cells

Mouse fibroblast (strain L-M) cells were grown in medium M150 plus 0.5% peptone for more than 6 months without either calcium (Ca) or magnesium (Mg) being added. The cells grew at rates similar to those in complete medium. The omission of Mg did not alter cell morphology, but Ca deficiency caused different morphology and growth patterns. After the contaminating Ca was totally removed with ethyleneglycol-bis(2-aminoethylether)tetraacetic acid, the cells could not survive more than 48 hours. At 0.02 mM Ca, the cells survived at least 5 days in culture. Cells growing in media with Ca levels of 0.04–0.08 mM were mostly round and grew in clumps. Ball-like aggregates were formed 7–10 days after subculturing. These growth patterns were completely reversed when the medium was changed to normal Ca concentration (1.25 mM). Karyotype analysis of the 2 types of cells revealed no difference; both had a modal number of 65 and showed the same marker chromosome. This, plus the reversibility of the change by addition or deletion of Ca, indicates that no population selection was involved.