Forskolin and thyrotrophin stimulation of rat FRTL-5 thyroid cell growth: the role of cyclic AMP

1987 ◽  
Vol 114 (2) ◽  
pp. 199-205 ◽  
Author(s):  
P. A. Ealey ◽  
C. A. Ahene ◽  
J. M. Emmerson ◽  
N. J. Marshall
Keyword(s):  
Cyclic Amp ◽  
Dose Range ◽  
Phosphodiesterase Inhibitor ◽  
Lag Phase ◽  
Thyroid Cell ◽  
Intracellular Camp ◽  
Camp Levels ◽  
Tsh Stimulation ◽  
Stimulation Of

ABSTRACT The adenylate cyclase stimulator forskolin increases intracellular cyclic AMP (cAMP) in rat FRTL-5 cells within minutes and, after a lag phase of 20–24 h, an increase of cells in metaphase is seen. The dose– response relationships were similar in both systems, with significant increases in the number of metaphases observed at ∼0·1 μmol/l and a doubling of cAMP levels at 1 μmol/l, whilst doses of 0·1 mmol/l and above proved cytotoxic. An involvement of intracellular cAMP as a positive intermediate in cell division was further suggested by the finding that a low dose of forskolin (0·1 μmol/l) potentiated TSH stimulation of mitosis. Isobutyl methyl xanthine (IBMX), a phosphodiesterase inhibitor, also acted as a mitogen and potentiated TSH action. Moreover, the simultaneous inclusion of low doses of IBMX and forskolin additionally potentiated TSH stimulation of mitosis. An analogue of cAMP, dibutyryl cAMP, also stimulated mitosis and acted over a restricted dose range, with maximal stimulation at 1 mmol/l. We conclude that cAMP may act as a positive signal for FRTL-5 thyroid cell proliferation. J. Endocr. (1987) 114, 199–205

scholarly journals Adenosine 3':5'-monophosphate content and actions in the division cycle of synchronized HeLa cells.

1976 ◽  
Vol 71 (2) ◽  
pp. 515-534 ◽  
Author(s):  
C E Zeilig ◽  
R A Johnson ◽  
E W Sutherland ◽  
D L Friedman
Keyword(s):  
Cell Cycle ◽  
Cyclic Amp ◽  
Hela Cells ◽  
S Phase ◽  
Intracellular Camp ◽  
Specific Effects ◽  
Low Concentrations ◽  
High Concentrations ◽  
Camp Levels ◽  
Stimulation Of

The involvement of adenosine 3':5'-monophosphate (cAMP) in the regulation of the cell cycle was studied by determining intracellular fluctuations in cAMP levels in synchronized HeLa cells and by testing the effects of experimentally altered levels on cell cycle traverse. Cyclic AMP levels were lowest during mitosis and were highest during late G-1 or early S phase. These findings were supported by results obtained when cells were accumulated at these points with Colcemid or high levels of thymidine. Additional fluctuations in cAMP levels were observed during S phase. Two specific effects of cAMP on cell cycle traverse were found. Elevation of cAMP levels in S phase or G-2 caused arrest of cells in G-2 for as long as 10 h and lengthened M. However, once cells reached metaphase, elevation of cAMP accelerated the completion of mitosis. Stimulation of mitosis was also observed after addition of CaCl2. The specificity of the effects of cAMP was verified by demonstrating that: (a) intracellular cAMP was increased after exposure to methylisobutylxanthine (MIX) before any observed effects on cycle traverse; (b) submaximal concentrations of MIX potentiated the effects of isoproterenol; and (c) effects of MIX and isoproterenol were mimicked by 8-Br-cAMP. MIX at high concentrations inhibited G-1 traverse, but this effect did not appear to be mediated by cAMP. Isoproterenol slightly stimulated G-1 traverse and partially prevented the MIX-induced delay. Moreover, low concentrations of 8-Br-cAMP (0.10-100 muM) stimulated G-1 traverse, whereas high concentrations (1 mM) inhibited. Both of these effects were also observed with the control, Br-5'-AMP, at 10-fold lower concentrations.

scholarly journals Cyclic AMP inhibits Cl-/HCO3- exchange at the apical membrane of Necturus gallbladder epithelium.

1987 ◽  
Vol 90 (2) ◽  
pp. 173-196 ◽  
Author(s):  
L Reuss
Keyword(s):  
Cyclic Amp ◽  
Apical Membrane ◽  
Phosphodiesterase Inhibitor ◽  
Intracellular Camp ◽  
Bathing Solution ◽  
Gallbladder Epithelium ◽  
Bathing Medium ◽  
Necturus Gallbladder ◽  
Mechanism Of Inhibition ◽  
Camp Levels

Intracellular microelectrode techniques were employed to study the effect of cyclic AMP on apical membrane Cl-/HCO3- exchange and electrodiffusive HCO3- transport in Necturus gallbladder epithelium. Intracellular cAMP levels were raised by addition of either the phosphodiesterase inhibitor theophylline (3 X 10(-3) M) or the adenylate cyclase activator forskolin (10(-5) M) to the serosal bathing solution. Measurements of pH in a poorly buffered control mucosal solution upon stopping superfusion show acidification, owing to secretion of both H+ and HCO3-. When the same experiment is performed after addition of amiloride or removal of Na+ from the mucosal bathing medium, alkalinization is observed since H+ transport is either inhibited or reversed, whereas HCO3- secretion persists. The changes in pH in both amiloride or Na-free medium were significantly decreased in theophylline-treated tissues. Theophylline had no effect on the initial rates of fall of intracellular Cl- activity (aCli) upon reducing mucosal solution [Cl-] to either 10 or 0 mM, although membrane voltage and resistance measurements were consistent with stimulation of apical membrane electrodiffusive Cl- permeability. Estimates of the conductive flux, obtained by either reducing simultaneously mucosal [Cl-] and [HCO3-] or lowering [Cl-] alone in the presence of a blocker of anion exchange (diphenylamine-2-carboxylate), indicate that elevation of intracellular cAMP inhibited the anion exchanger by approximately 50%. Measurements of net Cl- uptake upon increasing mucosal Cl- from nominally zero to levels ranging from 2.5 to 100 mM suggest that the mechanism of inhibition is a decrease in Vmax. Consistent with these results, the rate of intracellular alkalinization upon reducing external Cl- was also inhibited significantly by theophylline. Reducing mucosal solution [HCO3-] from 10 to 1 mM under control conditions caused intracellular acidification and an increase in aCli. Theophylline inhibited both changes, by 62 and 32%, respectively. These data indicate that elevation of intracellular cAMP inhibits apical membrane anion (Cl-/HCO3-) exchange. Studies of the effects of rapid changes in mucosal [HCO3-] on membrane voltages and the apparent ratio of membrane resistances, both in the presence and in the absence of theophylline, with or without Cl- in the mucosal solution, do not support the hypothesis that cAMP produces a sizable increase in apical membrane electrodiffusive HCO3- permeability.

scholarly journals The role of insulin in the modulation of glucagon-dependent control of phenylalanine hydroxylation in isolated liver cells

1987 ◽  
Vol 242 (3) ◽  
pp. 655-660 ◽  
Author(s):  
M J Fisher ◽  
A J Dickson ◽  
C I Pogson
Keyword(s):  
Cyclic Amp ◽  
Insulin Action ◽  
Phenylalanine Hydroxylase ◽  
Liver Cells ◽  
Phosphorylation State ◽  
Isolated Liver Cells ◽  
The Impact ◽  
Isolated Liver ◽  
Stimulation Of

The stimulation of phenylalanine hydroxylation in isolated liver cells by sub-maximally effective concentrations of glucagon (less than 0.1 microM) is antagonized by insulin (0.1 nM-0.1 microM). This phenomenon is a consequence of a decrease in the glucagon-stimulated phosphorylation of phenylalanine hydroxylase from liver cells incubated in the presence of insulin. The impact of insulin on the phosphorylation state and activity of the hydroxylase is mimicked by incubation of liver cells in the presence of orthovanadate (10 microM). A series of cyclic AMP and cyclic GMP analogues enhanced phenylalanine hydroxylation: in each case insulin diminished the stimulation of flux. These results are discussed in the light of the characteristics of insulin action on other metabolic processes.

Interaction of adenosine with vasopressin in the inner medullary collecting duct

1990 ◽  
Vol 259 (4) ◽  
pp. F679-F687 ◽  
Author(s):  
Y. Yagil
Keyword(s):  
Pertussis Toxin ◽  
Receptor Agonist ◽  
Collecting Duct ◽  
Phosphodiesterase Inhibitor ◽  
Inhibitory Effects ◽  
Inner Medullary Collecting Duct ◽  
Medullary Collecting Duct ◽  
Camp Levels ◽  
Dose Dependent ◽  
Stimulation Of

Administration of adenosine (Ado) into rat renal artery induces dose-dependent diuresis that is independent of changes in glomerular filtration rate or renal blood flow, suggesting a direct effect on tubule H2O reabsorption. To test the hypothesis that Ado modulates cellular action of arginine vasopressin (AVP) as a tubular mechanism for the diuretic effect of Ado, interaction of Ado with AVP was studied in primary cell culture of rat inner medullary collecting duct (IMCD) epithelium. Stimulation of cells with 10(-6) M AVP in presence of 0.1 mM Ro 20-1724, a nonmethylxanthine phosphodiesterase inhibitor that has no effect on Ado receptors, increased adenosine 3',5'-cyclic monophosphate (cAMP) levels twofold or more above baseline. Stimulation of cells with the A1 Ado-receptor agonist N6-cyclohexyladenosine (CHA), the A2-receptor agonist 5'-(N-ethylcarboxamido)-adenosine (NECA), or with the P-site agonist 2',5'-dideoxyadenosine (DDA) significantly inhibited the AVP-stimulated cAMP response. Preincubation with pertussis toxin abolished the inhibitory effects of CHA and NECA, but not of DDA. The data suggest that, in the rat IMCD, Ado modulates AVP action by interfering with its ability to stimulate formation of its second messenger, cAMP. This effect is mediated by the extracellular Ado receptors A1 and A2 and by the intracellular P-site. It occurs by at least two pathways, one sensitive and the other insensitive to pertussis toxin.

Possible role of cyclic GMP in stimulus-secretion coupling by salt gland of the duck

1979 ◽  
Vol 237 (5) ◽  
pp. C200-C204 ◽  
Author(s):  
D. J. Stewart ◽  
J. Sax ◽  
R. Funk ◽  
A. K. Sen
Keyword(s):  
Cyclic Amp ◽  
Guanylate Cyclase ◽  
Cyclic Gmp ◽  
Salt Gland ◽  
Domestic Ducks ◽  
Stimulus Secretion Coupling ◽  
Stimulation Of

Stimulation of salt galnd secretion in domestic ducks in vivo increased the cyclic GMP concentration of the tissue, but had no effect on cyclic AMP levels. Methacholine, which is known to stimulate sodium transport by the glands both in vivo and in vitro, stimulated ouabain-sensitive respiration in salt gland slices. Cyclic GMP stimulated ouabain-sensitive respiration to the same extent as methacholine. Guanylate cyclase stimulators, hydroxylamine and sodium azide, also stimulated ouabain-sensitive respiration. The stimulation of ouabain-sensitive respiration by methacholine was blocked either by atropine or by removal of calcium from the incubation medium. The stimulation of ouabain-sensitive respiration by cyclic GMP still occurred in the absence of calcium. The above observations seem to indicate that cyclic GMP acts as a tertiary link in the process of stimulus-secretion coupling in the tissue.

The Regulatory Role Of Camp In Induction Of Human Platelet Receptor For Fibrinogen

1981 ◽  
Author(s):  
S E Graber ◽  
J Hawiger
Keyword(s):  
Human Platelets ◽  
Membrane Receptor ◽  
Fibrinogen Receptor ◽  
Fibrinogen Binding ◽  
Platelet Receptor ◽  
The Relationship ◽  
Camp Levels ◽  
Dose Dependent ◽  
Stimulation Of

Membrane receptor for fibrinogen plays an essential role in adhesion and aggregation of human platelets by allowing fibrinogen to bridge two or more platelets together. Whereas in normal, unstimulated platelets fibrinogen receptor is not available, it becomes mobilized upon stimulation of platelets with thrombin, ADP, and other stimuli. The mechanism(s) regulating availability of membrane receptor for fibrinogen remains unknown. Following our recent demonstration that prostacyclin (PGI2) prevents mobilization of fibrinogen receptor by thrombin and ADP (Nature 1980, 283,195), we investigated the relationship between cAMP levels and fibrinogen receptor availability. Platelets separated from plasma proteins were briefly exposed to a low thrombin concentration (0.05 U/ml) followed by hirudin to inactivate free thrombin. Binding of 125I-fi- brinogen and cAMP levels were determined in parallel samples. A dose-dependent rise in platelet cAMP levels from 3.3 pM to 10.3 pM/108 platelets in response to PGI2 (3×10-9M - 3×108M) was accompanied by a corresponding inhibition of 125I-fibrinogen binding. The degree of the cAMP increment correlated with binding inhibition (r=0.96). The inhibition of 125I-fibrinogen binding by PGI2 was sustained up to 120 min and was paralleled by a persistent rise in cAMP level. Stimulation of platelet cAMP synthesis “from within” by a ribosylation of the nucleotide regulatory component with subunit A1 of cholera toxin also increased cAMP levels and inhibited fibrinogen receptor mobilization.These results provide evidence that “up and down” regulation of fibrinogen receptor in platelets is linked to changes in cAMP levels induced by different types of adenyl cyclase antagonists and agonists.

scholarly journals Increase in pituitary adenosine 3′:5′-cyclic monophosphate content and potentiation of growth-hormone release from heifer anterior pituitary slices incubated in the presence of 3-isobutyl-1-methylxanthine

1974 ◽  
Vol 142 (2) ◽  
pp. 295-300 ◽  
Author(s):  
J. George Schofield ◽  
Margaret McPherson
Keyword(s):  
Growth Hormone ◽  
Cyclic Amp ◽  
Prostaglandin E2 ◽  
Anterior Pituitary ◽  
Phosphodiesterase Inhibitor ◽  
Secretory Process ◽  
Hormone Release ◽  
Growth Hormone Release ◽  
Inhibitor Concentration ◽  
Stimulation Of

The release of growth hormone from heifer anterior pituitary slices and the cyclic AMP content of the slices were increased by the phosphodiesterase inhibitor 3-isobutyl-1-methylxanthine, both increases being related to inhibitor concentration over the range 0.1–1.0mm. Neither Ba2+(6.9 or 2.3mm), K+(72mm), nor p-chloromercuribenzoate (20μm) had any effect on pituitary cyclic AMP content over a 20min period. 3-Isobutyl-1-methylxanthine potentiated the release of growth hormone in response to Ba2+(2.3mm) and K+(24mm), but the degree of potentiation did not depend on inhibitor concentration in the same way as did tissue cyclic AMP content. 3-Isobutyl-1-methylxanthine decreased the concentration of K+required to give maximum stimulation of growth-hormone release, but did not significantly increase the maximum response to Ba2+. Growth-hormone release in the presence of prostaglandin E2 (1μm) was increased by 3-isobutyl-1-methylxanthine and was inhibited by the prostaglandin antagonist, 7-oxa-13-prostynoic acid, although this antagonist increased the pituitary cyclic AMP concentration and potentiated the prostaglandin E2-induced rise in cyclic AMP content. The stimulation of growth-hormone release by p-chloromercuribenzoate was not potentiated by 3-isobutyl-1-methylxanthine. The data suggest that Ba+and K+act at the same point in the secretory process as 3-isobutyl-1-methylxanthine, although by a different mechanism, and that p-chloromercuribenzoate has a different point of action.

scholarly journals Alteration of Platelet Cyclic AMP (cAMP) by Ethanol

1977 ◽  
Author(s):  
D.H. Cowan ◽  
M. Kikta ◽  
D. Baunach
Keyword(s):  
Cyclic Amp ◽  
Platelet Function ◽  
Inhibitory Effect ◽  
Human Platelets ◽  
Platelet Dysfunction ◽  
Camp Metabolism ◽  
Subnormal Level ◽  
Camp Levels ◽  
Stimulation Of

Studies of cAMP in human platelets exposed to ethanol were done to assess one possible mechanism for ethanol-related platelet dysfunction. Ingestion of ethanol by 3 subjects produced blood ethanol levels from 65-76 mM. Thrombocytopenia occurred in 1 subject and impaired platelet function occurred in all. Platelet cAMP decreased 36,51, and 59% below control levels. Infusion of ethanol to 2 normals produced blood ethanol levels of 43 mM and decreased platelet cAMP by 15% and 22%. Incubation of normal platelets with 86 mM ethanol in vitro decreased cAMP from 13.8 ± 2.9 (1 SD) to 9.4 ± 3.5 (p<0.02). By contrast, ethanol did not impair the increase in cAMP that occurred with 1.3 μM PGE1. Further, ethanol enhanced the increase in cAMP produced by 2.0 mM papaverine (Pap) by 160-220% and that produced by Pap + PGE1 by 58%. Dopamine, 0.1 mM, caused a 23% decrease in the basal level of cAMP, a 31% decrease below the subnormal level of cAMP seen with ethanol alone, and a 41% reduction in the increased level of cAMP produced by Pap + ethanol. The effect of ethanol on platelet cAMP metabolism is complex. Ethanol reduces basal levels of cAMP, does not decrease elevated levels that result from PGE1 stimulation of adenylate cyclase, and augments the inhibitory effect of Pap on platelet phosphodiesterase (PDE). Despite causing a decrease in basal cAMP levels, ethanol may impair platelet function by potentiating the effect of agents or other conditions which increase cAMP. The effect of ethanol on Pap-stimulated PDE activity may be blocked by dopamine, a neuropharmacologic agent that is actively accumulated by platelets.

scholarly journals Cyclic AMP enhances the sexual agglutinability of Chlamydomonas flagella.

1989 ◽  
Vol 109 (1) ◽  
pp. 247-252 ◽  
Author(s):  
U W Goodenough
Keyword(s):  
Cell Wall ◽  
Cyclic Amp ◽  
Mating Type ◽  
Feedback System ◽  
Intracellular Camp ◽  
Camp Generation ◽  
Sexual Agglutinability ◽  
Single Mating ◽  
Wall Loss ◽  
Camp Levels

Sexual adhesion between Chlamydomonas reinhardtii gametes elicits a rise in intracellular cAMP levels, and exogenous elevation of intracellular cAMP levels in gametes of a single mating type induces such mating responses as cell wall loss, flagellar tip activation, and mating structure activation (Pasquale, S. M., and U. W. Goodenough. 1987. J. Cell Biol. 105:2279-2292). Here evidence is presented that sexual adhesion mobilizes agglutinin to the flagellar surface, and that this mobilization can be induced by exogenous presentation of cAMP to gametes of a single mating type. It is proposed that Chlamydomonas adhesion entails a positive feedback system--initial contacts stimulate the presentation of additional agglutinin--and that this feedback is mediated by adhesion-induced cAMP generation.

Effect of gonadotrophin-releasing hormone (GnRH) and GnRH agonists upon accumulation of progesterone, cAMP and prostaglandin in isolated preovulatory rat follicles

1982 ◽  
Vol 101 (4) ◽  
pp. 603-610 ◽  
Author(s):  
Torbjörn Hillensjö ◽  
William J. LeMaire ◽  
Martin R. Clark ◽  
Kurt Ahrén
Keyword(s):  
Phosphodiesterase Inhibitor ◽  
Fold Increase ◽  
Control Group ◽  
Prostaglandin E ◽  
Gnrh Agonists ◽  
Bicarbonate Buffer ◽  
Preovulatory Follicles ◽  
Camp Levels ◽  
Dose Dependent ◽  
Stimulation Of

Abstract. To study the acute and direct effects of GnRH agonists preovulatory follicles were isolated from PMSG-treated immature rats and incubated for 15–360 min in modified Kreb's bicarbonate buffer. The levels of cAMP, prostaglandin E, and progesterone were analysed in the tissue and/or incubation media. GnRH and two GnRH agonists produced a dose-dependent stimulation of progesterone production with maximal levels 5–6-fold higher than the control group. As compared to LH the magnitude of this effect was small and was detected only after 240–360 min of incubation. GnRH also stimulated prostaglandin E accumulation and this effect was as pronounced as for LH. There were no detectable changes in cAMP levels for any concentration of GnRH when the incubation time varied between 15 and 120 min whether or not a phosphodiesterase inhibitor was present, but after 240 min of incubation a 2-fold incease in cAMP was found. Consistent with previous results, LH caused a pronouced (40–50-fold) increase in follicular cAMP which was already detectable after 15 min of incubation. Indomethacin abolished the rise in prostaglandin E induced either by GnRH or LH but did not affect the response in terms of cAMP or progesterone, and did not affect the stimulation of meiotic maturation of the follicle-enclosed oocytes caused by the hormones. It is concluded that GnRH can exert acute and LH-like stimulatory effects on the preovulatory rat follicle but that the mechanism of GnRH action is different from that of LH.

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