Effects of calcium ions on hamster cheek pouch epithelium grown in vitro.

Epithelial outgrowths from hamster cheek pouch explants were cultured for 14 days in media containing calcium concentrations of 0.05 mM, 0.075 mM, 0.1 mM, 0.25 mM, 0.75 mM or 1.45 mM (control). Compared with controls, the cultures grown at lower calcium concentrations (0.25-0.75 mM), exhibited higher mitotic indices and an increase in outgrowth size. The mitotic index of cultures at 0.25 mM calcium concentration was 30 +/- 2.26, compared to 24 +/- 2.24 for controls. Increase in size of the outgrowths was also observed at 0.25 mM calcium concentration compared with those grown in control medium. The epithelial outgrowths grown in control media exhibited cell stratification not observed at lower calcium concentrations. These studies indicate that lower calcium concentration in the media (0.25-0.75 mM) increased epithelial cell proliferation and inhibited keratinization.