Calcium transport and cellular distribution in quiescent and serum-stimulated primary cultures of bone cells and skin fibroblasts

✍ Scribed by Dr. Y. Eilam; N. Szydel

• Publisher: John Wiley and Sons
• Year: 1981
• Tongue: English
• Weight: 828 KB
• Volume: 106
• Category: Article
• ISSN: 0021-9541
• DOI: 10.1002/jcp.1041060208

✦ Synopsis

Primary cultures of bone cells and skin fibroblasts were examined for their Ca++ content, intracellular distribution and Ca++ fluxes. Kinetic analysis of 45Ca++ efflux curves indicated the presence of three exchangeable Ca++ compartments which turned over at different rates: a "very fast turnover" ( S , ) , a "fast turnover" (SJ, and a "slow turnover" Ca++ pool (S,). S, was taken to represent extracellular membrane-bound Ca++, S, represented cytosolic Ca++, and S, was taken to represent Ca++ sequestered in some intracellular organelles, probably the mitochondria. Bone cells contained about twice the amount of Ca++ as compared with cultured fibroblasts. Most of this extra Ca++ was localized in the "slow turnover" intracellular Ca++ pool (S,). Serum activation caused the following changes in the amount, distribution, and fluxes of Ca++: (1) In both types of cells serum caused an increase in the amount of Ca++ in the "very fast turnover" Ca++ pool, and an increase in the rate constant of 45Ca++ efflux from this pool, indicating a decrease in the strength of Ca++ binding to ligands on cell membranes. (2) In fibroblasts, serum activation also caused a marked decrease in the content of Ca++ in the "slow turnover" Ca++ pool (SJ, an increase in the rates of Ca++ efflux from the cells to the medium, and from S, to S,, as well as a decrease in the rate of influx into S,. (3) In bone cells the amount of Ca++ in S, remained high in "serum activated' cells, the rate of efflux from S, to S, increased, and the rate of influx into S , also