Cyclic AMP response in cells exposed to electric fields of different frequencies and intensities

1994 ◽  
Vol 33 (2) ◽  
pp. 141-147 ◽  
Author(s):  
G. Knedlitschek ◽  
M. Noszvai-Nagy ◽  
H. Meyer-Waarden ◽  
J. Schimmelpfeng ◽  
K. F. Weibezahn ◽  
...  
Keyword(s):  
Cyclic Amp ◽  
Electric Fields ◽  
In Cells

scholarly journals Heat treatment induces an increase in intracellular cyclic AMP content in human epidermoid A-431 cells

1991 ◽  
Vol 276 (3) ◽  
pp. 683-689 ◽  
Author(s):  
J G Kiang ◽  
Y Y Wu ◽  
M C Lin
Keyword(s):  
Heat Treatment ◽  
Cyclic Amp ◽  
Adenylate Cyclase ◽  
G Proteins ◽  
Phosphodiesterase Inhibitors ◽  
Metabolic Inhibitors ◽  
Thermally Induced ◽  
Heat Treated ◽  
Atp Breakdown ◽  
In Cells

The basal level of intracellular cyclic AMP (cAMPi) in A-431 cells incubated at 37 degrees C in Na(+)-containing Hanks solution is 2086 +/- 139 fmol/10(6) cells. When cells are exposed to 45 degrees C for 10 min, cAMPi increases by 40 +/- 4%, and then returns to basal levels within 30 min. Incubating cells in Ca(2+)-free or Mg(2+)-free Hanks solution has no effect on the heat-induced increase in cAMPi, but the increase is inhibited by acid-loading cells to intracellular pH 7.0 or 6.8. In unheated cells, cAMPi increases by 16 +/- 8%, 53 +/- 7%, or 39 +/- 8%, when incubated with isobutyl-1-methylxanthine (1 mM), Ro 20-1724 (0.5 mM), or theophylline (1 mM) respectively. However, heat treatment further elevates cAMPi in cells treated with phosphodiesterase inhibitors, indicating that heat treatment and phosphodiesterase inhibitors elevate cAMPi by a different pathway(s). Heat treatment increases adenylate cyclase activity 2.5-fold. When forskolin (150 microM), an adenylate cyclase stimulator, is applied to cells, the basal cAMPi increases 28 +/- 6-fold compared with controls. Subsequent heating of these cells lowers cAMPi levels to 7.0 +/- 0.5 times that in control cells. This decrease is prevented by pretreatment with pertussis toxin (30 ng/ml, 24 h), suggesting that G-proteins are involved in the process of heat-induced cAMPi increase. 2-Deoxy-D-glucose (10 mM), NaN3 (10 mM) and 2,4-dinitrophenol (1 mM) also increase cAMPi in A-431 cells. However, application of these metabolic inhibitors to cells before heat treatment does not result in cAMPi levels greater than that observed in cells with heat alone. Similar observations are obtained in heat-treated cells previously exposed to adenosine, but not to AMP or ADP. These data are the first to suggest that thermally induced increase in cAMPi is due to a combination of activation of adenylate cyclase and G-proteins, and an increase in adenosine owing to ATP breakdown caused by hyperthermia.

scholarly journals Trypsin-induced increase in cyclic AMP concentration in rat thymocytes An effect independent of calcium and calmodulin

1986 ◽  
Vol 239 (3) ◽  
pp. 603-607 ◽  
Author(s):  
J Segal
Keyword(s):  
Cyclic Amp ◽  
Free Medium ◽  
Standard Medium ◽  
Intracellular Pool ◽  
Calmodulin Inhibitor ◽  
Related Increase ◽  
In Cells

Trypsin produces a dose-related increase in cellular cyclic AMP concentration in rat thymocytes [Shneyour, Patt & Trainin (1976) J. Immunol. 117, 2143-2149; Segal & Ingbar (1983) Clin. Res. 31, 277A]. In the present study, I examined whether this effect of trypsin requires Ca2+ and whether it is modified by calmodulin. In fresh thymocytes suspended in standard medium (containing 1 mM-Ca2+), trypsin produced a concentration-dependent increase in cytoplasmic free Ca2+ concentration, which was evident at a concentration of 50 micrograms of trypsin/ml and reached maximal values at about 1 mg/ml. This effect of trypsin was very prompt in onset, almost immediate, and reached maximal values within 2-3 min. But in cells suspended in essentially Ca2+-free medium (6 nM free Ca2+), trypsin had no effect on cytoplasmic free Ca2+ concentration, which indicates that trypsin acted by increasing Ca2+ uptake rather than Ca2+ release from an intracellular pool. However, the increase in thymocyte cyclic AMP concentration produced by trypsin was independent of extracellular Ca2+ and was not influenced by calmodulin, because it was the same in the presence or absence of Ca2+ and was not changed by the calmodulin inhibitor trifluoperazine. I therefore suggest that in rat thymocytes the trypsin-induced increase in cyclic AMP concentration does not require Ca2+ and is not influenced by calmodulin.

Dibutyryl cyclic AMP inhibits transport dependent QO2 in cells isolated from the rabbit medullary ascending limb

1987 ◽  
Vol 409 (1-2) ◽  
pp. 74-80 ◽  
Author(s):  
Patricio Silva ◽  
Barbara Koenig ◽  
Stephanie Lear ◽  
Jill Eveloff ◽  
Rolf Kinne
Keyword(s):  
Cyclic Amp ◽  
Dibutyryl Cyclic Amp ◽  
In Cells

Studies on the levels of cyclic AMP in cells transformed by wild-type and temperature-sensitive Kirsten sarcoma virus

Cell ◽  
1974 ◽  
Vol 1 (1) ◽  
pp. 59-64 ◽  
Author(s):  
Richard A. Carchman ◽  
George S. Johnson ◽  
Ira Pastan ◽  
Edward M. Scolnick
Keyword(s):  
Cyclic Amp ◽  
Temperature Sensitive ◽  
Wild Type ◽  
Sarcoma Virus ◽  
In Cells

scholarly journals Coordinated Regulation of Rap1 and Thyroid Differentiation by Cyclic AMP and Protein Kinase A

2001 ◽  
Vol 21 (6) ◽  
pp. 1921-1929 ◽  
Author(s):  
Oxana M. Tsygankova ◽  
Arturo Saavedra ◽  
John F. Rebhun ◽  
Lawrence A. Quilliam ◽  
Judy L. Meinkoth
Keyword(s):  
Protein Kinase ◽  
Cyclic Amp ◽  
Feedback Regulation ◽  
Dominant Negative ◽  
Dependent Manner ◽  
Negative Feedback Regulation ◽  
Akt Phosphorylation ◽  
Rap1 Activation ◽  
Kinase A ◽  
In Cells

ABSTRACT Originally identified as an antagonist of Ras action, Rap1 exhibits many Ras-independent effects, including a role in signaling pathways initiated by cyclic AMP (cAMP). Since cAMP is a critical mediator of the effects of thyrotropin (TSH) on cell proliferation and differentiation, we examined the regulation of Rap1 by TSH in a continuous line of rat thyroid-like cells. Both cAMP and protein kinase A (PKA) contribute to the regulation of Rap1 activity and signaling by TSH. TSH activates Rap1 through a cAMP-mediated and PKA-independent mechanism. TSH phosphorylates Rap1 in a PKA-dependent manner. Interference with PKA activity blocked phosphorylation but not the activation of Rap1. Rather, PKA inhibitors prolonged Rap1 activation, as did expression of a Rap1A mutant lacking a PKA phosphorylation site. These results indicate that PKA elicits negative feedback regulation on cAMP-stimulated Rap1 activity in some cells. The dual regulation of Rap1 by cAMP and PKA extends to downstream effectors. The ability of TSH to stimulate Akt phosphorylation was markedly enhanced by the expression of activated Rap1A and was repressed in cells expressing a putative dominant-negative Rap1A mutant. Although the expression of activated Rap1A was sufficient to stimulate wortmannin-sensitive Akt phosphorylation, TSH further increased Akt phosphorylation in a phosphatidylinositol 3-kinase- and PKA-dependent manner. The ability of TSH to phosphorylate Akt was impaired in cells expressing a Rap1A mutant that could be activated but not phosphorylated. These findings indicate that dual signals, Rap1 activation and phosphorylation, contribute to TSH-stimulated Akt phosphorylation. Rap1 plays an essential role in cAMP-regulated differentiation. TSH effects on thyroid-specific gene expression, but not its effects on proliferation, were markedly enhanced in cells expressing activated Rap1A and repressed in cells expressing a dominant-negative Rap1A mutant. These findings reveal complex regulation of Rap1 by cAMP including PKA-independent activation and PKA-dependent negative feedback regulation. Both signals appear to be required for TSH signaling to Akt.

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