## Abstract The stimulation of DNA synthesis in quiescent, density‐arrested BALB/c‐3T3 cells by platelet‐derived growth factor in plasma‐supplemented medium was inhibited by the presence of isobutylmethylxanthine (IBMX) and cholera toxin, although neither IBMX or cholera toxin when used alone inhib
Inhibition of BALB/c-3T3 cells in late G1: Commitment to DNA synthesis controlled by somatomedin C
✍ Scribed by Walker Wharton; Judson J. Van Wyk; W. J. Pledger
- Publisher
- John Wiley and Sons
- Year
- 1981
- Tongue
- English
- Weight
- 735 KB
- Volume
- 107
- Category
- Article
- ISSN
- 0021-9541
No coin nor oath required. For personal study only.
✦ Synopsis
Abstract
Methylglyoxal bis‐(guanylhydrazone) (mGBG) blocked the stimulation of DNA synthesis in quiescent, density‐inhibited BALB/c‐3T3 cells treated with platelet‐derived growth factor (PDGF) and platelet‐poor plasma (PPP). Competence formation produced by a transient exposure to PDGF was not effected by mGBG. In contrast, mGBG effectively inhibited the PPP‐stimulated progression of competent cells through the G~1~ phase of the cell cycle, although maximal inhibition was observed when mGBG was present during both the exposure to PDGF‐ and PPP‐supplemented media. When quiescent cells were treated with PDGF and PPP‐supplemented media in the presence of mGBG for 12–18 hours and the mGBG was then removed, cells entered the S phase after a 4 hour lag. The rate of entry into the S phase, but not the time necessary for the cells to progress from the mGBG block into the S phase, was dependent on the concentration of PPP present after removal of the mGBG. Either somatomedin C or insulin, but not epidermal growth factor, fibroblast growth factor, or PDGF were able to substitute for PPP in allowing cells to enter the S phase after the cells were released from the mGBG block. A marked inhibition of (^3^H)‐leucine incorporation in serum‐stimulated cultures was produced at mGBG concentrations which caused no decrease in the amount of (^3^H)‐uridine incorporated during a short (15 minute) pulse. The ability of hormones to allow cells to progress to the late G~1~ phase and become committed to DNA synthesis after a mGBG inhibition was not related to their ability to restore the normal rate of protein synthesis as determined by (^3^H)‐leucine incorporation.
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## Abstract Platelet‐derived growth factor (PDGF) and platelet‐poor plasma, which lacks PDGF, both induce a rapid increase in the rate of total protein synthesis within quiescent, density‐arrested Balb/c‐3T3 cells. This stimulation of protein synthesis is associated with an increased aggregation of
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 p
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