Effect of ouabain on growth regulation by serum components in Balb/C-3T3 cells: Inhibition of entry into s phase by decreased protein synthesis
✍ Scribed by Christopher N. Frantz; Charles D. Stiles; W. J. Pledger; Charles D. Scher
- Publisher
- John Wiley and Sons
- Year
- 1980
- Tongue
- English
- Weight
- 895 KB
- Volume
- 105
- Category
- Article
- ISSN
- 0021-9541
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✦ Synopsis
The effect of inhibition of the cell membrane Na+-K+ pump on the Balbk-3T3 cell growth cycle was studied. Inhibition of the Na+-K+ pump resulted in a dose-dependent reduction of intracellular K+ concentration ({Kf},). However, inhibition of protein synthesis in Gi/G, and of subsequent entry into S phase occurred only after {K+}i fell below a critical threshold (50-60 mmoles/ liter). Thus, when the {K+}, falls below a critical threshold, protein synthesis is inhibited, preventing cells from entering the S phase.
The platelet-derived growth factor (PDGF) induces cells to become "competent" to traverse the cell cycle; the platelet-poor plasma component of serum allows competent cells to progress through G,/G, and enter S phase. Inhibition of the Na+-K+ pump did not prevent the induction of competence by PDGF, but it did reversibly inhibit plasma-mediated events in early GJG,. Similarly, cycloheximide inhibited plasma-mediated events but did not prevent PDGF-induced competence. Thus, protein synthesis may not be required for induction of competence; alternatively, the induction of the competent state may occur in these cells after removal of PDGF and protein synthesis inhibitor. Protein synthesis is required for subsequent plasma-mediated events in G,,/G,.