Effect of cell density on energy-dependent calcium uptake by Balb/c 3T3 membranes is independent of protein synthesis and attachment to substratum
✍ Scribed by Leon Moore; Ira Pastan
- Publisher
- John Wiley and Sons
- Year
- 1979
- Tongue
- English
- Weight
- 567 KB
- Volume
- 101
- Category
- Article
- ISSN
- 0021-9541
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✦ Synopsis
Abstract
Membranes isolated from subconfluent cultures of Balb/c 3T3 cells have low energy‐dependent calcium uptake activity. Replating confluent cells at low density results in a prompt fall of energy‐dependent calcium uptake by membrane fractions. The level to which uptake activity falls is a function of the density at which the cells are plated (Moore and Pastan, '77b). To determine if regulation of energy‐dependent uptake of calcium by membrane fractions is dependent upon attachment to a substrate and to further characterize conditions that regulate the process, we examined calcium uptake activity of membranes isolated from cells in suspension. With cells in suspension energy‐dependent calcium uptake activity of isolated membranes falls promptly if cells are diluted to a low density (<10^5^ cells/ml) and is a function of cell density. When cells in suspension at low cell densities are concentrated to high cell densities (>2 X 10^6^ cells/ml), calcium uptake activity of the isolated membrane fraction is increased as a function of cell density. These changes of membrane calcium uptake activity occur promptly and do not require protein synthesis.