Time-dependent effects of parathyroid hormone and prostaglandin E2on DNA synthesis by periosteal cells from embryonic chick calvaria

✍ Scribed by A. Scutt; C. Duvos; J. Lauber; H. Mayer

• Publisher: Springer
• Year: 1994
• Tongue: English
• Weight: 637 KB
• Volume: 55
• Category: Article
• ISSN: 1432-0827
• DOI: 10.1007/bf00425877

✦ Synopsis

Both PGE z and PTH (1-34) caused a time-and concentration-dependent stimulation of proliferation by embryonic chick periosteal cells. Cells were exposed to the agents for different periods of time, the medium was replaced with fresh medium, and 3H-TdR incorporation was measured after 16 hours. Challenge with 10 -6 M prostaglandin Ez (PGE2) or 10 -7 M parathyroid hormone (1-34) (PTH) for 5 minutes produced 4-and 5.5-fold increases in 3H-TdR incorporation, respectively. Longer exposures, however, produced diminishing responses and after 45 minutes, only minimal effects or slight inhibitions were seen. These timedependent effects were also seen with forskolin and dibutyryl-cAMP; TPA on the other hand stimulated DNA synthesis after both short-and long-term exposure. Both PGE2 and PTH (1-34) stimulated cAMP synthesis in periosteal cells but neither could be shown to stimulate protein kinase-C (PKC) at concentrations required for stimulation of proliferation, and dibutyryl-cyclic AMP (cAMP) effectively inhibited endogenous PKC activity. It is possible that the stimulation of proliferation by short-term exposure to PGE2 and PTH (1-34) is mediated by cAMP and that the time dependency possibly stems from the inhibition of endogenous PKC activity by increased intracellular cAMP levels.