scholarly journals Cyclic 3',5' AMP relay in Dictyostelium discoideum. I. A technique to monitor responses to controlled stimuli.

1979 ◽  
Vol 80 (2) ◽  
pp. 291-299 ◽  
Author(s):  
P N Devreotes ◽  
P L Derstine ◽  
T L Steck
Keyword(s):  
Dictyostelium Discoideum ◽  
Secretory Response ◽  
Intracellular Camp ◽  
Perfusion System ◽  
Perfusion Technique ◽  
Basal Secretion ◽  
Cyclic Monophosphate ◽  
Quantitative Studies

A perfusion technique was developed to deliver [14C]adenosine 3',5'-cyclic monophosphate (cAMP) stimuli of well-defined magnitude and duration to tritium-labeled Dictyostelium discoideum amoebae and simultaneously monitor the elicited secretion of [3H]cAMP (i.e., the relay response). The tritiated compounds secreted in response to [14C]cAMP stimuli were highly enriched in [3H]cAMP and reflected an increase in intracellular cAMP accompanying stimulation rather than the release of a preexisting store or bulk cellular contents. The secretory response (per 10(6) cells) to 2-min stimuli increased during differentiation from about 0.2 pmol at 0.5 h to approximately 5 pmol of cAMP at 7 h. Without adequate perfusion, amoebae altered the level of cAMP in their environment in two ways: phosphodiesterases destroyed cAMP stimuli under some conditions so as to attenuate the relay response; under other circumstances, secreted cAMP magnified minimal exogenous stimuli into maximal responses. Amoebae, furthermore, would respond to their basal secretion of cAMP autocatalytically if its removal or destruction were interrupted. The perfusion system minimized these cell-induced modifications, allowing control of the level of the stimulus and response in quantitative studies.

scholarly journals Cyclic 3', 5'-AMP relay dictyostelium discoideum. V. Adaptation of the cAMP signaling response during cAMP stimulation

1980 ◽  
Vol 86 (2) ◽  
pp. 554-561 ◽  
Author(s):  
M Dinauer ◽  
TL Steck ◽  
P Devreotes
Keyword(s):  
Adenylate Cyclase ◽  
Test Stimulus ◽  
Dictyostelium Discoideum ◽  
Time Course ◽  
Intracellular Camp ◽  
Perfusion Technique ◽  
Adaptation Mechanism ◽  
Cellular Processes ◽  
Extracellular Camp ◽  
Camp Stimulation

In dictyostelium discoideum, extracellular cAMP activates adenylate cyclase, which leads to an increase in intracellular cAMP and the rate of cAMP secretion. The signaling response to a constant cAMP stimulus is terminated after several minutes by an adaptation mechanism. The time- course of adaptation stimuli of 10(-6) or 10(-7) M cAMP was assessed. We used a perfusion technique to deliver defined cAMP stimuli to [(3)H]adenosine-labeled amoebae and monitored their secretion of [(3)H]cAMP. Amoebae were pretreated with 10(-6) or 10(-7) M cAMP to periods of 0.33-12 minutes, and then immediately given test stimuli of 10(-8) M to 2.5 x 10(-7) M cAMP. The response to a given test stimulus was progressively attenuated and finally extinguished as the duration of the pretreatment stimulus increased. During concentration of the test stimulus. The responses to test stimuli of 10(-8), 5 x 10(-8), 10(-7), or 2.5 x 10(-7) M cAMP were extinguished after approximately 1, 2.25,2.5, and 10 min, respectively. 1.5 min of stimulation with 10(-7) M cAMP was necessary to extinguish the response of a test stimulus of 10(-8) M cAMP. Our data suggest that adaptation begins within 20 s of stimulation, rises rapidly for approximately 2.5 min, and reaches a plateau after approximately 10 min. The absolute rate of rise was faster during pretreatment with 10(-6) than with 10(-7) M cAMP. These results support a working hypothesis in which the occupancy of surface cAMP receptors leads to changes in two opposing cellular processes, excitation and adaptation, that control the activity of D. discoideum adenylate cyclase.

PERFUSION OF OVARIES IN VITRO AND IN VIVO

1972 ◽  
Vol 68 (2_Supplb) ◽  
pp. S285-S309 ◽  
Author(s):  
Kurt Ahrén ◽  
Per Olof Janson ◽  
Gunnar Selstam
Keyword(s):  
Perfusion System ◽  
Perfusion Technique ◽  
Preliminary Results ◽  
Advantages And Disadvantages

ABSTRACT This paper discusses in vivo and in vitro ovarian perfusion systems described so far in the literature. The interest is not focussed primarily on the results of these studies but rather on the advantages and disadvantages of the techniques and methods used. Another part of the paper summarizes the points which are most important, in our opinion, to take into consideration when developing an in vitro perfusion technique of the ovary. The last part of the paper gives a description of and some preliminary results from an in vitro perfusion system of the rabbit ovary which is under development in this laboratory.

scholarly journals Intracellular calcium and adenosine 3′,5′-cyclic monophosphate as mediators of potassium-induced aldosterone secretion

1985 ◽  
Vol 228 (1) ◽  
pp. 69-76 ◽  
Author(s):  
I Kojima ◽  
K Kojima ◽  
H Rasmussen
Keyword(s):  
Arachidonic Acid ◽  
Cyclic Amp ◽  
Intracellular Calcium ◽  
Secretory Response ◽  
Ionophore A23187 ◽  
Small Decrease ◽  
Aldosterone Secretion ◽  
Cyclic Monophosphate ◽  
A Value ◽  
Glomerulosa Cells

We compared the action of K+ on aldosterone secretion from isolated bovine adrenal glomerulosa cells with that of ionophore A23187. Addition of either 50 nM-A23187 or 8 mM-K+ to perifused cells induces a similar initial aldosterone-secretory responses, and a similar sustained increases in Ca2+ entry. However, K+-induced secretion is more sustained than is A23187-induced secretion, even though each agonist appears to act by increasing Ca2+ entry into the cells. When [3H]inositol-labelled cells are stimulated by 8 mM-K+, a small decrease in phosphatidylinositol 4,5-bisphosphate [PtdIns(4,5)P2] is observed. This decrease is not accompanied by an increase in inositol trisphosphate (InsP3) concentration. Also, if [3H]arachidonic acid-labelled cells are exposed to 8 mM-K+, there is no increase in [3H]diacylglycerol production. When [3H]inositol-labelled cells are stimulated by 50 nM-A23187, a small decrease in PtdIns(4,5)P2 is observed. This decrease is not accompanied by an increase in InsP3. The cyclic AMP content of K+-treated cells was approximately twice that in A23187-treated cells. If cells are perifused simultaneously with 50 nM-forskolin and 50 nM-A23187, the initial aldosterone-secretory response is similar to that induced by A23187 alone, and the response is sustained rather than transient, and is similar to that seen during perifusion of cells with 8 mM-K+. This dose of forskolin (50 nM) causes an elevation of cyclic AMP concentration in A23187-treated cells, to a value similar to that in K+-treated cells. These results indicate that, in K+-treated cells, a rise in cyclic AMP content serves as a positive sensitivity modulator of the Ca2+ message, and plays a key role in mediating the sustained aldosterone-secretory response.

Pharmacological characterization of cyclic AMP receptors mediating gene regulation in Dictyostelium discoideum

1986 ◽  
Vol 6 (7) ◽  
pp. 2402-2408
Author(s):  
B Haribabu ◽  
R P Dottin
Keyword(s):  
Gene Expression ◽  
Cyclic Amp ◽  
Cell Surface ◽  
Dictyostelium Discoideum ◽  
Cell Surface Receptor ◽  
Intracellular Camp ◽  
Response Curves ◽  
Pharmacological Characterization ◽  
Surface Receptor ◽  
Extracellular Molecules

Extracellular molecules regulate gene expression in eucaryotes. Exogenous cyclic AMP (cAMP) affects the expression of a large number of developmentally regulated genes in Dictyostelium discoideum. Here, we determine the specificity of the receptor(s) which mediates gene expression by using analogs of cAMP. The order of potency with which these analogs affect the expression of specific genes is consistent with the specificity of their binding to a cell surface receptor and is distinct from their affinity for intracellular cAMP-dependent protein kinase. Dose-response curves with cAMP and adenosine 3',5'-monophosphorothioate, a nonhydrolyzable analog, revealed that the requirement for high concentrations of exogenous cAMP for regulating gene expression is due to the rapid degradation of cAMP by phosphodiesterase. The addition of low concentrations of cAMP (100 nM) or analogs in pulses also regulates gene expression. Both the genes that are positively regulated by exogenous cAMP and the discoidin gene, which is negatively regulated, respond to cAMP analogs to the same degree. Genes expressed in prespore or prestalk cells are also similarly regulated. These data suggest that the effects are mediated through the same receptor. The specificity of this receptor is indistinguishable from that of the well-characterized cell surface cAMP receptor.

Pentoxifylline inhibits FMLP-induced macromolecular leakage

1995 ◽  
Vol 269 (1) ◽  
pp. H239-H245
Author(s):  
K. Nakagawa ◽  
F. N. Miller ◽  
A. W. Knott ◽  
M. J. Edwards
Keyword(s):  
Inflammatory Responses ◽  
Fluorescein Isothiocyanate ◽  
Histamine Receptor ◽  
Intracellular Camp ◽  
Dependent Manner ◽  
Cyclic Monophosphate ◽  
Endogenous Histamine ◽  
Camp Analogue

The acute inflammatory responses to the chemotactic peptide N-formyl-methionyl-leucyl-phenylalanine (FMLP) and the effects of pentoxifylline (PTXF) on the responses in vivo were studied. We used intravital microscopy with rat cremaster muscle preparation to determine inflammatory responses of microcirculation. Macromolecular leakage from postcapillary venules was evaluated by quantifying the extravasation of fluorescein isothiocyanate conjugated to bovine serum albumin. FMLP induced a rapid increase in macromolecular leakage, an increase in leukocyte-endothelium adhesion, and a decrease in blood flow in the microcirculation. PTXF inhibited FMLP-induced responses in a dose-dependent manner but failed to block the histamine-dependent leakage induced by compound 48/80. In addition, diphenhydramine, a histamine-receptor blocker, did not affect the macromolecular leakage induced by FMLP. The cell-permeable adenosine 3',5'-cyclic monophosphate (cAMP) analogue N6,2'-O-dibutyryladenosine 3',5'-cyclic monophosphate mimicked PTXF's effects on the microcirculation and also inhibited FMLP-induced macromolecular leakage. PTXF is known to inhibit phosphodiesterase and increase intracellular cAMP, which modulates functions of endothelial cells, smooth muscle cells, and neutrophils in vitro. Our findings suggest that FMLP induces acute inflammatory responses through activation of neutrophils, independent of endogenous histamine release, and that PTXF inhibits these responses through elevated intracellular cAMP.

scholarly journals B2 kinin receptor upregulation by cAMP is associated with BK-induced PGE2 production in rat mesangial cells

1998 ◽  
Vol 274 (3) ◽  
pp. F532-F540 ◽  
Author(s):  
Maria E. Marin Castaño ◽  
Joost P. Schanstra ◽  
Christophe Hirtz ◽  
João B. Pesquero ◽  
Christiane Pecher ◽  
...  
Keyword(s):  
Mrna Expression ◽  
Receptor Binding ◽  
Binding Sites ◽  
Mesangial Cells ◽  
Regulation Of Gene Expression ◽  
Prostaglandin E ◽  
Intracellular Camp ◽  
Cyclic Monophosphate ◽  
New Information ◽  
Camp Formation

In the rat mesangial cell (MC), activation of the bradykinin B2 receptor (B2R) by bradykinin (BK) is associated with both phospholipase C (PLC) and A2(PLA2) activities and with inhibition of adenosine 3′,5′-cyclic monophosphate (cAMP) formation leading to cell contraction. Because cAMP plays an important role in the regulation of gene expression in general, we investigated the effect of increasing the intracellular cAMP concentration ([cAMP]i) in mesangial cells on the B2 mRNA expression, on the density of B2receptor binding sites, on the BK-induced increase in both the free cytosolic Ca2+ concentration ([Ca2+]i), and in the prostaglandin E2(PGE2) production. Forskolin, PGE2, and cAMP analog, 8-bromoadenosine 3′,5′-cyclic monophosphate (8-BrcAMP), were used to increase [cAMP]i. Twenty-four-hour treatment with forskolin, PGE2, and 8-BrcAMP resulted in significant increases in B2receptor binding sites, which were inhibited by cycloheximide. The maximum B2 receptor mRNA expression (160% above control) was observed in cells treated during 24 h with forskolin and was prevented by actinomycin D. In contrast, thed- myo-inositol 1,4,5-trisphosphate (IP3) formation and the BK-induced increase in [Ca2+]i, reflecting activation of PLC, were not affected by increased levels of [cAMP]i. However, the BK-induced PGE2 release, reflecting PLA2 activity, was significantly enhanced. These data bring new information regarding the dual signaling pathways of B2receptors that can be differentially regulated by cAMP.

Effects of cAMP on serotonin evoked calcium transients in cultured rat airway smooth muscle cells

1997 ◽  
Vol 272 (5) ◽  
pp. L865-L871 ◽  
Author(s):  
B. Tolloczko ◽  
Y. L. Jia ◽  
J. G. Martin
Keyword(s):  
Smooth Muscle ◽  
Protein Kinase ◽  
Airway Smooth Muscle ◽  
Airway Smooth Muscle Cells ◽  
Intracellular Camp ◽  
Dependent Protein Kinase ◽  
Cyclic Monophosphate ◽  
Dependent Protein ◽  
High Concentrations

Agents increasing intracellular adenosine 3',5'-cyclic monophosphate (cAMP) cause relaxation of airway smooth muscle. However, the mechanisms of their action are not fully understood. We investigated the role of cAMP in the modulation of intracellular Ca2+ concentration ([Ca2+]i) transients evoked by serotonin (5-HT) in cultured rat tracheal smooth muscle (TSM) cells. Forskolin (10(-7) M) caused a significant elevation of intracellular cAMP and a 60% relaxation of tracheal rings contracted with 5-HT but did not affect [Ca2+]i in TSM cells. Forskolin (10(-5) M) completely relaxed tracheal rings and significantly decreased [Ca2+]i during the sustained phase of the 5-HT response. Forskolin-induced relaxation was attenuated by the cAMP-dependent protein kinase A (PKA) inhibitor Rp diastereomer of cAMP (Rp-cAMPS; 10(-4) M) and by the guanosine 3',5'-cyclic monophosphate (cGMP)-dependent protein kinase (PKG) inhibitor [Rp isomer of 8-(4-chlorophenylthio)-guanosine 3',5'-cyclic monophosphorothioate, 10(-4) M]. The effects of forskolin on [Ca2+]i were not altered by the PKA inhibitor but were abolished by the PKG inhibitor and thapsigargin. These results indicate that, in rat TSM, the relaxant effects of high concentrations of cAMP may be mediated, at least in part, by facilitating the sequestration of Ca2+ into intracellular stores by a mechanism involving PKG.

Mechanisms of synergism between glucose and cAMP on stimulation of insulin release

1984 ◽  
Vol 247 (6) ◽  
pp. E701-E708 ◽  
Author(s):  
W. Phang ◽  
L. Domboski ◽  
Y. Krausz ◽  
G. W. Sharp
Keyword(s):  
Pancreatic Islets ◽  
Insulin Release ◽  
Ringer Solution ◽  
Intracellular Camp ◽  
Cyclic Monophosphate ◽  
Rat Pancreatic Islets ◽  
Individual Effects ◽  
The Individual ◽  
Isolated Rat ◽  
Stimulation Of

The mechanism of synergism between glucose and adenosine 3',5'-cyclic monophosphate (cAMP) on insulin release has been studied. Synergism may result from 1) inhibition of Na+-Ca2+ exchange by glucose and 2) a cAMP-induced sensitization of the release machinery to Ca2+. To distinguish between these two possibilities, isolated rat pancreatic islets were perifused with agents that raise intracellular levels of cAMP [3-isobutyl-1-methylxanthine (IBMX) and forskolin] and others that increase intracellular concentrations of Ca2+ either by blocking Na2+-Ca2+ exchange (ouabain and choline-Ringer solution) or by causing increased Ca2+ influx (KCl, carbachol, and 10 mM Ca2+). The results indicate that both the combination of cAMP and increased Ca2+ influx or blocked Na2-Ca2+ exchange and increased Ca2+ influx potentiated insulin release. When the relative potentiating abilities of cAMP and blocked Na2+-Ca2+ exchange were compared by determining the individual effects of IBMX and 1 mM ouabain (a concentration that causes similar inhibition of 45C2+ efflux as 16.7 mM glucose) in the presence of carbachol, cAMP was only 1.4 times more potent as a potentiating agent than blocked Na+-Ca2+ exchange. The greatest potentiation of insulin release was observed when Na+-Ca2+ exchange was blocked in the presence of increased levels of intracellular cAMP.

Increased cAMP levels in stimulated neutrophils inhibit their adhesion to human bronchial epithelial cells

1997 ◽  
Vol 272 (4) ◽  
pp. L580-L587 ◽  
Author(s):  
P. G. Bloemen ◽  
M. C. van den Tweel ◽  
P. A. Henricks ◽  
F. Engels ◽  
M. H. Kester ◽  
...  
Keyword(s):  
Epithelial Cells ◽  
Adrenergic Receptor ◽  
Phosphodiesterase Inhibitor ◽  
Bronchial Epithelial Cells ◽  
Intercellular Adhesion Molecule ◽  
Neutrophil Adhesion ◽  
Intracellular Camp ◽  
Human Bronchial Epithelial Cells ◽  
Bronchial Epithelial ◽  
Cyclic Monophosphate

Bronchial epithelial cells express the intercellular adhesion molecule-1 that mediates binding of activated neutrophils via interaction with Mac-1 and/or leukocyte function-associated antigen-1. In this study, we examined whether increased intracellular levels of adenosine 3',5'-cyclic monophosphate (cAMP) affected neutrophil adhesion to the human bronchial epithelial cells. It was found that the N-formylmethionyl-leucyl-phenylalanine (fMLP)-stimulated neutrophil adhesion was concentration dependently inhibited when the cAMP analogs dibutyryl adenosine 3',5'-cyclic monophosphate or 8-bromoadenosine 3',5'-cyclic monophosphate were present. The beta-adrenergic receptor agonists isoprenaline and salmeterol, in the presence of the phosphodiesterase inhibitor 3-isobutyl-1-methylxanthine (IBMX), were also able to inhibit the fMLP-stimulated adhesion of neutrophils to bronchial epithelial cells. These agonists in combination with IBMX significantly increased the intracellular cAMP level in both neutrophils and epithelial cells. Preincubation of neutrophils with the long-acting beta2-adrenergic receptor agonist salmeterol (in the presence of IBMX) inhibited their fMLP-stimulated adhesion to epithelial cells, whereas pretreatment of epithelial cells did not influence the adhesion process. When ethanol-fixed epithelium was used, salmeterol pretreatment also diminished the adhesion of stimulated neutrophils. Moreover, combinations of salmeterol or isoprenaline with IBMX inhibited fMLP-upregulated Mac-1 expression. Therefore, we conclude from these data that elevation of intracellular cAMP in the neutrophil inhibits stimulated neutrophil adhesion to bronchial epithelial cells via Mac-1.

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