title: Extracellular calcium alters the effects of retinoic acid on DNA synthesis in cultured murine keratinocytes.
abstract: The rate of proliferation of epidermal keratinocytes was manipulated by growing the cells in medium containing high or low concentrations of calcium. Keratinocytes cultured in high extracellular Ca++ (1.4 mM and 2.8 mM) proliferated twice as fast as those grown in low Ca++ medium (0.09 mM) as measured by incorporation of [3H]thymidine into DNA. Exposure of high calcium keratinocytes to all-trans retinoic acid for 4 days caused a dose-related inhibition of DNA synthesis with an IC50 of about 10 microM. In contrast, incubating low calcium keratinocytes with all-trans retinoic acid caused a dose-related stimulation of DNA synthesis with maximum increase of 278% over control at 10 microM. This increase was accompanied by increases in culture confluency with maximum increase of 109% in cell number over control at 10 microM. These results are of importance since they suggest Ca++ may influence the effect of retinoids on keratinocytes.
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002478:Cells, Cultured; D004261:DNA Replication / Q000187:drug effects*; D004305:Dose-Response Relationship, Drug; D000078404:Epidermal Cells; D005110:Extracellular Space / Q000378:metabolism*; D007536:Isomerism; D007633:Keratins; D051379:Mice; D008807:Mice, Inbred BALB C; D013936:Thymidine / Q000378:metabolism; D014212:Tretinoin / Q000494:pharmacology*
chemical_list: D014212:Tretinoin; D007633:Keratins; D002118:Calcium; D013936:Thymidine