Effects of PGI2 and Its More Stable Forms on the Aggregation and on the Camp Content of Human Platelets

1979 ◽  
Author(s):  
E. Nemesánszky ◽  
I. Blaskó ◽  
I. Stadler ◽  
G. Sas ◽  
L. A. Pálos
Keyword(s):  
Ethyl Ester ◽  
Inhibitory Effect ◽  
Human Platelets ◽  
Intracellular Camp ◽  
Camp Content ◽  
Prolonged Duration ◽  
Potent Inhibitory Effect ◽  
Stable Forms ◽  
Derivatives Of ◽  
Intracellular Camp Content

The authors investigated the anti-aggregating properties of some relatively stable derivatives of PGI2 concurrently determining the intracellular cAMP content of platelets. The ethyl-ester derivative of PGI2 and the complexes of PGI2-ethyl ester with β-cyclodextrine proved to be more stable than PGI2-sodium salt. Their stimulating effect on adenyl-cyclase correlated with the potent inhibitory effect on platelet aggregation as well. The enhancing effect of these compounds for the intracellular cAMP content have a prolonged duration time -lasting 300 minutes- compared with the only a few minutes’ effect of PGE1.These stable forms of PGI2 might be clinically useful as highly effective antiaggregating compounds.

Effects of PGI2 and its more Stable forms on the Aggregation and on the Camp Content of Human Platelets

1979 ◽  
Author(s):  
E. Nemesánszky ◽  
Gy. Blaskó ◽  
I. Stadler ◽  
G. Sas ◽  
L.A. Pálos
Keyword(s):  
Ethyl Ester ◽  
Inhibitory Effect ◽  
Human Platelets ◽  
Adenyl Cyclase ◽  
Intracellular Camp ◽  
Camp Content ◽  
Potent Inhibitory Effect ◽  
Stable Forms ◽  
Derivatives Of ◽  
Intracellular Camp Content

The authors investigated the anti-aggregating properties of some relatively stable derivatives of PGI2 concurrently determining the intracellular cAMP content of platelets. The ethyl-ester derivative of PGI2 and the complexes of PGI2-ethyl ester with β-cyclodextrine proved to be mora stable than PGI2-sodium salt. Their stimulating effect on adenyl-cyclase correlated with the potent inhibitory effect on platelet aggregation as well. The enhancing effect of these compounds for the intracellular cAMP conten t have a prolonged dura tion time -las ting 300 minutes - compared with the only a few minutes’ effect of PGE1.These stable forms of PGI2 might be clinically useful as highly effective anti-aggregating compounds.

Mobilization of Fibrinogen Receptor Sites on Human Platelets Stimulated with ADP is Prevented by Prostacyclin

1979 ◽  
Author(s):  
J. Hawiger ◽  
S. Parkinson ◽  
S. Timmons
Keyword(s):  
Inhibitory Effect ◽  
Human Platelets ◽  
Affinity Constant ◽  
Human Fibrinogen ◽  
Fibrinogen Receptor ◽  
Receptor Sites ◽  
Plasma Factor ◽  
Potent Inhibitory Effect

Fibrinogen is a plasma factor required for aggregation of human platelets by ADP. The mechanism of platelet-ADP-fibrinogen interaction was studied by measuring the equilibrium binding of 125I-fibrinogen to human platelets separated from plasma proteins. Binding of 125I-fibrinogen to platelets not stimulated with ADP was low and unaffected by an excess of unlabel led fibrinogen. However, when platelets were stimulated with 4μM of ADP, there was an eightfold increase In the number of available binding sites for human fibrinogen, with affinity constant of 1.9 x 109M-1. This striking increase in fibrinogen receptor sites on human platelets was specific for ADP as contrasted to ATP, AMP, and adenosine. Prostacyclin (Prostaglandin I2, PGI2), a novel prostaglandin produced by the blood vessel wall, completely blocked this ADP-induced increase in fibrinogen receptor sites on human platelets. The effect of PGI2 was prompt and concentration dependent, reaching maximum at 10-9M. 6-keto PGF2 a stable derivative ot PGI2, did not have such an effect. Thus movement of fibrinogen receptor sites on human platelet membrane stimulated with ADP is prevented by PGI2. This represents a new biologic property of this vascular hormone and contributes to better understanding of its potent inhibitory effect in vitro and in vivo on ADP-induced platelet aggregation requiring mobilization of fibrinogen receptor.

scholarly journals Thrombin regulates intracellular cyclic AMP concentration in human platelets through phosphorylation/activation of phosphodiesterase 3A

Blood ◽  
2007 ◽  
Vol 110 (5) ◽  
pp. 1475-1482 ◽  
Author(s):  
Wei Zhang ◽  
Robert W. Colman
Keyword(s):  
Cyclic Amp ◽  
Platelet Activation ◽  
Selective Inhibition ◽  
Human Platelets ◽  
Intracellular Camp ◽  
Akt Inhibitor ◽  
Camp Content ◽  
Fibrinogen Receptor ◽  
Thrombin Activation ◽  
Camp Hydrolysis

Abstract Thrombin-induced cyclic AMP (cAMP) reduction potentates several steps in platelet activation, including Ca++ mobilization, cytoskeletal reorganization, and fibrinogen receptor conformation. We now reinvestigate the signaling pathways by which intracellular cAMP content is controlled after platelet activation by thrombin. When washed human platelets were stimulated with thrombin, cAMP-dependent phosphodiesterase (PDE3A) activity was significantly increased. A nonselective PDE inhibitor, 3-isobutyl-1-methylxanthine (IBMX), and the PDE3 selective inhibitors milrinone and cilostazol each suppressed thrombin-induced cAMP-dependent PDE responses, but not 2 different PDE2 inhibitors. Selective inhibition of PDE3A resulted in reversal of thrombin-induced cAMP reduction, indicating that thrombin activated PDE3A. In synergy with inhibition of adenylate cyclase by thrombin, activated PDE3A accelerates cAMP hydrolysis and maximally reduces the cAMP content. Thrombin-induced PDE3A activation was diminished concomitantly with dephosphorylation of PDE3A by protein phosphatase 1 (PP1). An Akt inhibitor blocked PDE3A activation and constrained thrombin-induced cAMP reduction. A P2Y12 inhibitor also reduced thrombin-induced cAMP reduction. The combination of both reversed cAMP decrease by thrombin. Thrombin-mediated phosphorylated PDE3A was isolated by liquid chromatography, detected by a monoclonal antibody against Akt-phosphorylated substrate, and verified by immunoprecipitation study. The predominant isoform phosphorylated by Akt was the 136-kDa species. We suggest that activation/phosphorylation of PDE3A via Akt signaling pathway participates in regulating cAMP during thrombin activation of platelets.

Selective activation of the prostaglandin E2 receptor subtype EP2 or EP4 leads to inhibition of platelet aggregation

2010 ◽  
Vol 104 (10) ◽  
pp. 796-803 ◽  
Author(s):  
Koh-ichi Yuhki ◽  
Fumiaki Kojima ◽  
Takehiro Yamada ◽  
Takayuki Fujino ◽  
Akiyoshi Hara ◽  
...  
Keyword(s):  
Platelet Aggregation ◽  
Inhibitory Effect ◽  
Human Platelets ◽  
Receptor Subtype ◽  
Intracellular Camp ◽  
Dependent Manner ◽  
Selective Activation ◽  
Inhibitory Potency ◽  
Ic50 Values ◽  
Induced Aggregation

SummaryThe effect of selective activation of platelet prostaglandin (PG) E2 receptor subtype EP2 or EP4 on platelet aggregation remains to be determined. In platelets prepared from wild-type mice (WT platelets), high concentrations of PGE2 inhibited platelet aggregation induced by U-46619, a thromboxane receptor agonist. However, there was no significant change in the inhibitory effect of PGE2 on platelets lacking EP2 (EP2 –/– platelets) and EP4 (EP4 –/– platelets) compared with the inhibitory effect on WT platelets. On the other hand, AE1–259 and AE1–329, agonists for EP2 and EP4, respectively, potently inhibited U-46619 -induced aggregation with respective IC50 values of 590 ± 14 and 100 ± 4.9 nM in WT platelets, while the inhibition was significantly blunted in EP2 –/– and EP4 –/– platelets. In human platelets, AE1–259 and AE1–329 inhibited U-46619-induced aggregation with respective IC50 values of 640 ± 16 and 2.3 ± 0.3 nM. Notably, the inhibitory potency of AE1–329 in human platelets was much higher than that in murine platelets, while such a difference was not observed in the inhibitory potency of AE1–259. AE1–329 also inhibited adenosine diphosphate-induced platelet aggregation, and the inhibition was almost completely blocked by AE3–208, an EP4 antagonist. In addition, AE1–329 increased intracellular cAMP concentrations in a concentration- and EP4-dependent manner in human platelets. These results indicate that selective activation of EP2 or EP4 can inhibit platelet aggregation and that EP4 agonists are particularly promising as novel anti-platelet agents.

Effects of calcium antagonist TMB-8 on active Na and Cl transport in rabbit ileum

1986 ◽  
Vol 250 (5) ◽  
pp. G691-G697 ◽  
Author(s):  
M. Donowitz ◽  
S. Cusolito ◽  
G. W. Sharp
Keyword(s):  
Short Circuit ◽  
Short Circuit Current ◽  
Electrolyte Transport ◽  
Intracellular Camp ◽  
Bathing Solution ◽  
Rabbit Ileum ◽  
Camp Content ◽  
Cl Transport ◽  
Transport Effects ◽  
Intracellular Camp Content

The effects of 3,4,5-trimethoxybenzoate 8-(N,N-diethylamino)octyl ester (TMB-8), an agent that traps calcium within intracellular stores, were studied on active electrolyte transport in rabbit ileum under basal conditions and after altering transport by increasing the intracellular cAMP content or by exposure to two agonists that act by altering intracellular Ca2+ (carbachol and serotonin). TMB-8 decreased the ileal short-circuit current and increased active Na and Cl absorption by increasing the mucosal-to-serosal Na and Cl fluxes. These effects were reversed by increasing the bathing solution Ca2+ to 4 mM, a concentration that itself did not alter basal ileal transport. The maximum glucose- and amino acid (alanine)-induced increase in Na absorption in the ileum was not affected by TMB-8. The effects on basal transport of TMB-8 were not associated with a change in 45Ca2+ entry across the ileal serosal surface. TMB-8 did not alter cAMP-induced secretion, as judged by its lack of effect on the increase in short-circuit current caused by 8-bromo-cAMP (10(-4) M). TMB-8 totally prevented the transport effects of carbachol but did not inhibit the effects of serotonin. These data suggest a role for intracellular Ca2+ in regulation of basal ileal Na and Cl transport but not in cAMP-induced secretion. There appear to be several pools of intracellular Ca2+ involved in neurohumoral effects on active electrolyte transport.

Xanthine derivatives without PDE effect stimulate voltage-activated chloride conductance of toad skin

2003 ◽  
Vol 284 (2) ◽  
pp. C521-C527 ◽  
Author(s):  
Wolfram Nagel ◽  
Uri Katz
Keyword(s):  
Intracellular Camp ◽  
Voltage Sensitivity ◽  
Inhibitory Effects ◽  
Amphibian Skin ◽  
Toad Skin ◽  
Camp Content ◽  
Xanthine Derivatives ◽  
X 32 ◽  
Intracellular Camp Content ◽  
Stimulation Of

The effect of xanthine derivatives on the voltage-activated Cl− conductance ( G Cl) of amphibian skin was analyzed. 3-Isobutyl-1-methylxanthine (IBMX) and the recently synthesized xanthine derivatives 3,7-dimethyl-1-propyl xanthine (X-32) and 3,7-dimethyl-1-isobutyl xanthine (X-33), which lack inhibitory effects on phosphodiesterases in CHO and Calu-3 cells, increased voltage-activated G Cl without effect on baseline conductance at inactivating voltage. Half-maximal stimulation of G Cl occurred at 108 ± 9 μM for X-32 and X-33 after apical or basolateral application. The stimulation of G Cl, which occurs only in the presence of Cl− in the mucosal solution, is caused by a shift of the voltage sensitivity to lower clamp potentials and an increase of the maximally activated level. Furosemide reversed both the shift of sensitivity and the increase in magnitude. These patterns are fundamentally different from those seen after application of membrane-permeant, nonmetabolized analogs of cAMP, and they indicate that the xanthines stimulate G Cl directly. This notion is strengthened by the lack of influence on intracellular cAMP content, which is consistent with the observations in CHO and Calu-3 cells. We propose that the xanthine derivatives increase the voltage sensitivity of a regulative component in the conductive Cl− pathway across amphibian skin.

scholarly journals Mechanism of bile salt-induced mucin secretion by cultured dog gallbladder epithelial cells

1996 ◽  
Vol 316 (3) ◽  
pp. 873-877 ◽  
Author(s):  
J. Henriëtte KLINKSPOOR ◽  
Guido N. J. TYTGAT ◽  
Sum P. LEE ◽  
Albert K. GROEN
Keyword(s):  
Epithelial Cells ◽  
Bile Salt ◽  
Bile Salts ◽  
Cholesterol Gallstone ◽  
Direct Interaction ◽  
Gallstone Formation ◽  
Intracellular Camp ◽  
Mucin Secretion ◽  
Camp Content ◽  
Intracellular Camp Content

1. Hypersecretion of gallbladder mucin has been proposed to be a pathogenic factor in cholesterol gallstone formation. Using cultured gallbladder epithelial cells, we demonstrated that bile salts regulate mucin secretion by the gallbladder epithelium. In the present study we have investigated whether established second messenger pathways are involved in bile salt-induced mucin secretion. 2. The effect of activators and inhibitors on mucin secretion was studied by measuring the secretion of [3H]N-acetyl-D-glucosamine-labelled glycoproteins. Intracellular cAMP content of the cells was measured using a radioimmunoassay. 3. Incubation of the cells with 10 mM taurocholate did not increase the intracellular cAMP content (25.7 versus control 22.8 pmol of cAMP/mg of protein). No stimulation of mucin secretion was observed after incubation with 1–100 μM concentrations of the calcium ionophores ionomycin and A23187. The stimulatory effect of 10 mM tauroursodeoxycholate (TUDC) on mucin secretion could not be inhibited by the addition of EDTA. Activation of protein kinase C (PKC) by 1 μg/ml phorbol 12-myristate 13-acetate (PMA) caused an increase in mucin secretion (342% versus control 100%), comparable with the effect of 40 mM TUDC. The effect of 10 ng/ml PMA could partially be inhibited by a concentration of 2 μM of the PKC inhibitor staurosporin. Staurosporin had no inhibitory effect on mucin secretion induced by TUDC. 4. In gallbladder epithelial cells bile salts do not stimulate mucin secretion via one of the classical signal transduction pathways. We hypothesize that bile salts act on mucin secretion via a direct interaction with the apical membrane.

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