Gs and Gi coupling of adrenomedullin in adult rat ventricular myocytes

2006 ◽  
Vol 290 (5) ◽  
pp. H1842-H1847 ◽  
Author(s):  
Shivani Mittra ◽  
Jean-Pierre Bourreau
Keyword(s):  
Ventricular Myocytes ◽  
Negative Inotropic Effect ◽  
Inotropic Effect ◽  
Paracrine Factor ◽  
Inotropic Effects ◽  
Prolonged Incubation ◽  
Rat Ventricular Myocytes ◽  
Cell Shortening ◽  
Adult Rat

Adrenomedullin (ADM) acts as an autocrine or a paracrine factor in the regulation of cardiac function. The intracellular mechanisms involved in the direct effect of ADM on adult rat ventricular myocytes (ARVMs) are still to be elucidated. In ARVMs from normal rats, ADM produced an initial (<30 min) increase in cell shortening and Ca2+ transients and a marked decrease in both on prolonged incubation (>1 h). Both effects were sensitive to ADM antagonist ADM-(22–52). Treatment with SQ-22536, an inhibitor of adenylate cyclase, blocked the positive inotropic effect of ADM and potentiated its negative inotropic effect. The negative inotropic effect was sensitive to inhibition by pertussis toxin (PTX), an inhibitor of Gi proteins and KT-5720, an inhibitor of PKA. The observations suggest a switch from Gs-coupled to PTX-sensitive, PKA-dependent Gi coupling by ADM in ARVMs. The ADM-mediated Gi-signaling system involves cAMP-dependent pathways because SQ-22536 further increased the negative inotropic actions of ADM. Also, because ADM is overproduced by ARVMs in our rat model of septic shock, ARVMs from LPS-treated rats were subjected to treatment with ADM-(22–52) and PTX. The decrease in cell shortening and Ca2+ transients in LPS-treated ARVMs could be reversed back with ADM-(22–52) and PTX. This indicates that ADM plays a role in mediating the negative inotropic effect in LPS-treated ARVM through the activation of Gi signaling. This study delineates the intracellular pathways involved in ADM-mediated direct inotropic effects on ARVMs and also suggests a role of ADM in sepsis.

Role of cyclooxygenase in ventricular effects of adrenomedullin: is adrenomedullin a double-edged sword in sepsis?

2004 ◽  
Vol 286 (3) ◽  
pp. H1034-H1042 ◽  
Author(s):  
Shivani Mittra ◽  
Jean-Marc Hyvelin ◽  
Qixian Shan ◽  
Fai Tang ◽  
Jean-Pierre Bourreau
Keyword(s):  
Cardiac Tissue ◽  
Ventricular Myocytes ◽  
Marked Decrease ◽  
Negative Inotropic Effect ◽  
Inotropic Effect ◽  
Prolonged Incubation ◽  
Cell Contractility ◽  
Rat Ventricular Myocytes ◽  
Cell Shortening ◽  
Cox Inhibitor

Adrenomedullin (ADM) is upregulated in cardiac tissue under various pathophysiological conditions. However, the direct inotropic effect of ADM on normal and compromised cardiomyocytes is not clear. In rat ventricular myocytes, ADM produced an initial (<30 min) increase in cell shortening and Ca2+ transient and, on prolonged incubation (>1 h), a marked decrease in cell shortening and Ca2+ transient. Both effects were sensitive to inhibition by the ADM antagonist ADM-(22–52). The increase and decrease in cell shortening and Ca2+ transient were attenuated by pretreatment with indomethacin [a nonspecific cyclooxygenase (COX) inhibitor], nimesulide and SC-236 (specific COX-2 inhibitors), and tranylcypromine (a prostacyclin synthase inhibitor); SQ-29548 (a thromboxane receptor antagonist) was without effect. Cells isolated from LPS-treated rats that were in the late, hypodynamic phase of septic shock also showed a marked decrease in cell shortening and Ca2+ transient. Because ADM is overexpressed in sepsis, we repeated the above protocol in cells isolated from LPS-treated rats. At 4 h after LPS injection, ADM levels markedly increased in plasma, ventricles, and freshly isolated ventricular myocytes. Decreases in cell shortening and Ca2+ transient in LPS-treated cells were reversed by pretreatment with ADM-(22–52). Anti-ADM (rat) IgG also reversed the decrease in cell shortening and other parameters of cell kinetics. Indomethacin, SC-236, and tranylcypromine restored cell contractility and the decrease in Ca2+ transient, whereas SQ-29548 had no effect, implying that prostacyclin played a role in both effects. However, with regard to cell-shortening kinetics, indomethacin and SQ-29548 decreased the amount of time taken by the cells to return to baseline, whereas SC-236 and tranylcypromine did not, implying that not only prostacyclin, but also thromboxane, is involved. The results indicate that ADM interacts with COX to yield prostanoids, which mediate its negative inotropic effect in LPS-treated rat ventricular myocytes.

Protein kinase Cε and the antiadrenergic action of adenosine in rat ventricular myocytes

2004 ◽  
Vol 287 (4) ◽  
pp. H1721-H1729 ◽  
Author(s):  
Koji Miyazaki ◽  
Satoshi Komatsu ◽  
Mitsuo Ikebe ◽  
Richard A. Fenton ◽  
James G. Dobson
Keyword(s):  
Electrical Stimulation ◽  
Protein Kinase ◽  
Ventricular Myocytes ◽  
Adrenergic Agonist ◽  
Inhibitory Peptide ◽  
Rat Ventricular Myocytes ◽  
Adult Rat ◽  
Tubular System ◽  
Stimulation Of

Adenosine-induced antiadrenergic effects in the heart are mediated by adenosine A1 receptors (A1R). The role of PKCε in the antiadrenergic action of adenosine was explored with adult rat ventricular myocytes in which PKCε was overexpressed. Myocytes were transfected with a pEGFP-N1 vector in the presence or absence of a PKCε construct and compared with normal myocytes. The extent of myocyte shortening elicited by electrical stimulation of quiescent normal and transfected myocytes was recorded with video imaging. PKCε was found localized primarily in transverse tubules. The A1R agonist chlorocyclopentyladenosine (CCPA) at 1 μM rendered an enhanced localization of PKCε in the t-tubular system. The β-adrenergic agonist isoproterenol (Iso; 0.4 μM) elicited a 29–36% increase in myocyte shortening in all three groups. Although CCPA significantly reduced the Iso-produced increase in shortening in all three groups, the reduction caused by CCPA was greatest with PKCε overexpression. The CCPA reduction of the Iso-elicited shortening was eliminated in the presence of a PKCε inhibitory peptide. These results suggest that the translocation of PKCε to the t-tubular system plays an important role in A1R-mediated antiadrenergic actions in the heart.

Do β2-adrenergic receptors modulate Ca2+ in adult rat ventricular myocytes?

1998 ◽  
Vol 274 (4) ◽  
pp. H1308-H1314 ◽  
Author(s):  
Michael A. Laflamme ◽  
Peter L. Becker
Keyword(s):  
Pertussis Toxin ◽  
Calcium Homeostasis ◽  
Adrenergic Receptors ◽  
Calcium Current ◽  
Ventricular Myocytes ◽  
Camp Accumulation ◽  
Camp Production ◽  
Rat Ventricular Myocytes ◽  
Adult Rat

We examined the role of β2-adrenergic receptors (ARs) in modulating calcium homeostasis in rat ventricular myocytes. Zinterol (10 μM), an agonist with a 25-fold greater affinity for β2-ARs over β1-ARs, modestly enhanced L-type calcium current ( I Ca) magnitude by ∼30% and modestly accelerated the rate of Ca2+ concentration ([Ca2+]) decline (∼35%) but had little effect on the magnitude of the [Ca2+] transient (a nonsignificant 6% increase). However, 1 μM of the highly selective β1-AR antagonist CGP-20712A completely blocked the I Ca increase induced by 10 μM zinterol. Pretreatment of cells with pertussis toxin (PTX) did not alter I Ca enhancement by 10 μM zinterol, although it did abolish the ability of acetylcholine to block the forskolin-induced enhancement of I Ca. Zinterol (10 μM) approximately doubled adenosine 3′,5′-cyclic monophosphate (cAMP) accumulation, although one-half of this increase was blocked by CGP-20712A. In contrast, 1 μM of the nonselective β-agonist isoproterenol increased cAMP production 15-fold. Thus we found no evidence that activation of β2-ARs modulates calcium homeostasis in rat ventricular myocytes, even after treatment with PTX.

scholarly journals Role of epicardial mesothelial cells in the modification of phenotype and function of adult rat ventricular myocytes in primary coculture.

1992 ◽  
Vol 71 (1) ◽  
pp. 40-50 ◽  
Author(s):  
H Eid ◽  
D M Larson ◽  
J P Springhorn ◽  
M A Attawia ◽  
R C Nayak ◽  
...  
Keyword(s):  
Ventricular Myocytes ◽  
Mesothelial Cells ◽  
Rat Ventricular Myocytes ◽  
Adult Rat ◽  
And Function

Effects of TNF-alpha on [Ca2+]i and contractility in isolated adult rabbit ventricular myocytes

1996 ◽  
Vol 271 (4) ◽  
pp. H1449-H1455 ◽  
Author(s):  
J. I. Goldhaber ◽  
K. H. Kim ◽  
P. D. Natterson ◽  
T. Lawrence ◽  
P. Yang ◽  
...  
Keyword(s):  
Methyl Ester ◽  
Ventricular Myocytes ◽  
Negative Inotropic Effect ◽  
Cell Length ◽  
Inotropic Effect ◽  
Tnf Alpha ◽  
Adult Rabbit ◽  
Cell Shortening ◽  
Rabbit Ventricular Myocytes ◽  
In Cells

The mechanism of the acute negative inotropic effect of tumor necrosis factor-alpha (TNF-alpha) was studied in enzymatically isolated adult rabbit ventricular myocytes. In cells loaded with fura 2 acetoxymethyl ester (AM) and paced intermittently at 0.2 Hz, TNF-alpha at doses < or = 10,000 U/ml caused a significant reduction in active cell shortening at 20 min, without reducing the amplitude of the accompanying intracellular Ca2+ concentration ([Ca2+]i) transient. Similar results were obtained in cells loaded with indo 1-AM and paced continuously at 0.2 Hz during exposure to TNF-alpha (10,000 U/ml). The effect of TNF-alpha on cell shortening could be prevented by the nitric oxide (NO) synthase blocker NG-nitro-L-arginine methyl ester (L-NAME) but not its inactive enantiomer NG-nitro-D-arginine methyl ester (D-NAME). The NO scavenger hemoglobin also attenuated the effects of TNF-alpha. TNF-alpha also caused a significant increase in diastolic cell length without any change in diastolic [Ca2+]i. The effect on cell length was prevented by L-NAME but not D-NAME. In cells loaded with the pH indicator seminaphthorhodafluor-AM, TNF-alpha did not alter pH sufficiently to account for the negative inotropic effect. These data suggest that high doses of TNF-alpha can acutely induce NO synthesis in isolated myocytes and reduce contractility by decreasing myofilament [Ca2+]i responsiveness. The mechanism of this altered myofilament [Ca2+]i response is unknown but does not appear to be pH mediated.

Abstract 2192: Fcgamma Receptor II On Cardiomyocytes

Circulation ◽  
2007 ◽  
Vol 116 (suppl_16) ◽  
Author(s):  
Christiane Trimpert ◽  
Stephan B Felix ◽  
Andreas Greinacher ◽  
Katrin Birkenmeier ◽  
Alexander Staudt
Keyword(s):  
Tyrosine Kinases ◽  
Kinase Inhibitors ◽  
Kinase Inhibitor ◽  
Negative Inotropic Effect ◽  
Cell Types ◽  
Inotropic Effect ◽  
Rat Cardiomyocytes ◽  
Inotropic Effects ◽  
Human Cardiomyocytes ◽  
Adult Rat

Introduction : Recently we detected the FcγII receptor on rat and human cardiomyocytes. Binding of cardiac antibodies obtained from DCM-patients to this receptor induced negative inotropic effects. The mechanism of these effects remains to be elucidated. Methods: Isolated adult rat cardiomyocytes stained with Fura-2-AM were field-stimulated (1 Hz, 12 V). The relative change of the calcium transients and systolic cell shortening due to superfusion with a polyclonal goat-antibody against the FcγII receptor (10 μg/ml) were recorded with a dual-excitation fluorescence microscope. For inhibition of possible involved tyrosine kinases we used PP2 (1μM) and specific syk-Kinase inhibitors. Results: Superfusion of rat cardiomyocytes with anti-FcγII-receptor antibody induces a negative inotropic effect. The tested concentrations (6 μg/ml, 8 μg/ml, 10 μg/ml and 16 μg/ml) show a clear dose-response-relationship. The contractility of the cells decreases after 2 min by −5,3%, −11,5%, −14,2% and −18,3% from baseline as well as the Ca 2+ -Ratio (−9,5%, −11,2%, −12,2%, −15,6%). The negative inotropic reaction could be blocked by preincubation of the cells with the tyrosine kinase inhibitor PP2 (change of contractility/Ca2+-Ratio from baseline: −1, 3%/−2,4%, p<0,001). Cells preincu-bated with specific inhibitors for syk-Kinases did not show a negative inotropic reaction after superfusion with the antibody (change of contractility/Ca 2+ -ratio from baseline +0,7%/−5,5%, p<0,05). A polyclonal goat control antibody (anti-CD45, c = 10 μg/ml)) did not trigger a reaction (change from baseline for contractility/Ca2+-Ratio: −3%/−2,4%, p<0,001). Conclusion: The inhibition of the negative inotropic effect of antibodies against FcγII receptor shows an involvement of Kinases in the signalling pathway like described for other cell types.

Role of PDE3 and PDE4 for β-adrenergic control of cAMP and ICa,L in adult rat ventricular myocytes

2007 ◽  
Vol 42 (6) ◽  
pp. S49
Author(s):  
Jérôme Leroy ◽  
Aniella Abi-Gerges ◽  
Wito Richter ◽  
Viacheslav O. Nikolaev ◽  
Stefan Engelhardt ◽  
...  
Keyword(s):  
Ventricular Myocytes ◽  
Rat Ventricular Myocytes ◽  
Adult Rat ◽  
Adrenergic Control
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