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  • 1
    Electronic Resource
    Electronic Resource
    Pharmacological Profile of CGP 48506, A New Positive Inotropic Agent (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Cardiovascular drug reviews 15 (1997), S. 0 
    Details
    ISSN: 1527-3466
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1527-3466.1997.tb00330.x
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  • 2
    Electronic Resource
    Electronic Resource
    Ischemic Preconditioning by Unstable Angina Reduces the Release of CK-MB Following CABG and Stimulates Left Ventricular HSP-72 Protein Expression (2005)
    350 Main Street , Malden , MA 02148-5020 , USA and 9600 Garsington Road , Oxford OX4 2XG , England . : Blackwell Science Inc
    Journal of cardiac surgery 20 (2005), S. 0 
    Details
    ISSN: 1540-8191
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract  Background and Aim: Whether the CK-MB reducing effect of ischemic preconditioning (IP) by unstable angina within 24 to 48 hours before CABG is achieved by early or by delayed preconditioning of left ventricular myocardium in humans is unknown. We investigated whether IP is associated with phosphorylation of p38 MAPK (characteristic for early preconditioning) or with increased protein expression of HSP-72 (characteristic for delayed preconditioning) at the time of CABG in patients. Methods: Nineteen patients were grouped according to the occurrence of ischemic episodes within 48 hours before CABG. The patients without angina were assigned to the control group (CON, n = 10) whereas patients who had experienced angina within 48 hours before CABG were assigned to the preconditioned group (IP, n = 9). The effect of IP on the CABG induced maximal release of creatine kinase (CK) and CK-MB was examined. Left ventricular biopsy specimens taken immediately before cross clamping from ischemic (ISCH) and from reference (REF) areas were processed to analyze p38 MAPK phosphorylation and HSP-72-protein expression. Results: While IP significantly reduced CK-MB (18.7 ± 1.3 vs. 13.8 ± 1.5 U/L, mean ± SEM, p 〈 0.05), it only tended to reduce CK (292.7 ± 32.8 vs. 274.1±31.1 U/L, p = NS, mean ± SEM). CK-MB release for any given cross-clamp time was significantly reduced by IP (regression lines: CON, y= 0.4x+ 2, r= 0.8; IP, y= 0.1x+ 10, r= 0.2; p 〈 0.01, ANCOVA). There was no effect of IP on left ventricular p38 MAPK phosphorylation. IP increased left ventricular HSP-72-protein expression in ischemic areas when compared to reference areas (1.78 ± 0.35 vs. 2.58 ± 0.65, REF vs. ISCH, PhosphorImager units ×106, mean ± SEM, p 〈 0.05, ANCOVA). Conclusions: Thus, in the human left ventricular myocardium there is a second window of protection lasting for at least 48 hours, while at that time the early phase of preconditioning has already gone.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1540-8191.2005.2004107.x
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  • 3
    Electronic Resource
    Electronic Resource
    Role of guanine nucleotide-binding protein in the regulation by adenosine of cardiac potassium conductance and force of contraction. Evaluation with pertussis toxin (1986)
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 332 (1986), S. 403-405 
    Details
    ISSN: 1432-1912
    Keywords: Pertussis toxin ; Adenosine ; Negative inotropic effect ; Potassium conductance ; Guinea-pig heart
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary In atrial cardiac preparations adenosine exerts a receptor-mediated negative inotropic effect due to an increased potassium conductance. Pretreatment of guinea pigs with pertussis toxin abolished the negative inotropic and action potential shortening effect of adenosine and the adenosine analogue (−)-N6-phenylisopropyladenosine (PIA). As pertussis toxin specifically inactivates guanine nucleotide-binding proteins involved in the signal transfer from receptor binding to specific cell functions, it is concluded that a guanine nucleotide-binding protein is involved in the regulation of the receptor-mediated change in potassium conductance and force of contraction.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00500095
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  • 4
    Electronic Resource
    Electronic Resource
    Effects of adenosine analogues on contractile response and CAMP content in guinea-pig isolated ventricular myocytes (1989)
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 340 (1989), S. 689-695 
    Details
    ISSN: 1432-1912
    Keywords: Adenosine analogues ; cAMP ; Isolated ventricular myocytes ; Contractile response ; Guinea-pig hearts ; Isoprenaline ; Phosphodiesterase inhibitor
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary In the present study the effects of adenosine analogues were investigated on cAMP content and contractile response in guinea-pig ventricular myocytes. The adenosine analogues (−)-N6-phenylisopropyladenosine (R-PIA), 5′-N-ethylcarboxamideadenosine (NECA) and (+)-N6-phenyl-isopropyladenosine (S-PIA) in the presence of 0.01 μmol/l isoprenaline reduced contractile response concentration-dependently. R-PIA and NECA were about equipotent (IC25: 0.01 μmol/l and 0.039 μmol/l respectively), while S-PIA was less potent (IC25: 0.6 μmol/l). Isoprenaline stimulated cAMP content was reduced by R-PIA (IC25: 0.004 μmol/l) and with lower potency by S-PIA (IC25: 0.15 μmol/l) but the extent of reduction of cAMP by R-PIA and S-PIA (to 55% and 64% respectively) was less than the reduction of contractile response (to 26% and 55% respectively). This suggests that the effects of R- and S-PIA on contractile response are only in part due to a reduction in cAMP content. In addition, NECA did not decrease cAMP content but decreased contractile response to the same extent as R-PIA. Similar results were obtained in the presence of the phosphodiesterase inhibitor Ro 20-1724. Time course studies revealed that the effects of R-PIA (1 μmol/l) on cAMP content and contractile response coincided reaching steady state after 5 min and remained stable thereafter. The effects of NECA (1 µmol/l) on contractility also reached steady state within 5 min, whereas it did not change cAMP content. It is concluded that the reduction of contractility by adenosine analogues in the presence of isoprenaline can only in part be explained by a reduction of cAMP content. It is suggested that a cAMP-independent effect, possibly an activation of phosphatases, might be involved additionally.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00717746
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  • 5
    Electronic Resource
    Electronic Resource
    The influence of second-nearest neighbor interactions on the thermodynamic properties of B2 phases with substitutional defects (1976)
    Springer
    Monatshefte für Chemie 107 (1976), S. 1471-1485 
    Details
    ISSN: 1434-4475
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract In order to explain some discrepancies between the theoretical predictions and the experimental data for the thermodynamic properties of substitutional B 2 phases,Chang's theoretical model is extended by including the influence of second-nearest neighbor interactions. For this purpose a new parameter η is introduced which is defined as the ratio of the interchange energies between second-nearest and first-nearest neighbors. Theoretical equations are derived for the compositional dependence of the activity and the partial molar enthalpy. Using literature data, the following phases are re-evaluated in terms of the disorder parameter α and the newly introduced parameter η: β′-AuZn, β′-AuCd, β′-AgMg, and β′-NiZn. Very good agreement is found between the theoretical curves and the experimental data for the four systems. The values of η obtained range from 0.0 for β′-NiZn to 0.5 for β′-AuZn. The inclusion of second-nearest neighbor interactions has little influence on the values of α. It is shown that the behavior of the activity curve in β′-AuZn can be explained in a physically more meaningful way by including interactions between all second-nearest neighbors rather than interactions between gold substitutional defects only, as was done byLibowitz.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01153926
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  • 6
    Electronic Resource
    Electronic Resource
    Mechanism underlying the reduced positive inotropic effects of the phosphodiesterase III inhibitors pimobendan, adibendan and saterinone in failing as compared to nonfailing human cardiac muscle preparations (1991)
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 344 (1991), S. 90-100 
    Details
    ISSN: 1432-1912
    Keywords: Phosphodiesterase inhibition ; Failing and nonfailing human heart ; Positive inotropic effect ; Cyclic adenosine monophosphate content ; Combination of isoprenaline and phosphodiesterase inhibitors
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The present study was performed to compare the effects of the new positive inotropic phosphodiesterase III inhibitors pimobendan, adibendan, and saterinone on the isometric force of contraction in electrically driven ventricular trabeculae carneae isolated from explanted failing (end-stage myocardial failure) with those from nonfailing (prospective organ donors) human hearts. In preparations from nonfailing hearts the phosphodiesterase inhibitors, as well as the aβ-adrenoceptor agonist isoprenaline, the cardiac glycoside dihydroouabain, and calcium, which were studied for comparison, revealed pronounced positive inotropic effects. The maximal effects of pimobendan, adibendan, and saterinone amounted to 56%, 36% and 45%, respectively, of the maximal effect of calcium. In contrast, in preparations from failing hearts the phosphodiesterase III inhibitors failed to significantly increase the force of contraction and the effect of isoprenaline was markedly reduced. The effects of dihydroouabain and calcium were almost unaltered. The diminished effects of isoprenaline were restored by the concomitant application of phosphodiesterase inhibitors. To elucidate the underlying mechanism of the lack of effect of the phosphodiesterase III inhibitors in the failing heart we also investigated the inhibitory effects of these compounds on the activities of the phosphodiesterase isoenzymes I–III separated by DEAE-cellulose chromatography from both kinds of myocardial tissue. Furthermore, the effects of pimobendan and isoprenaline on the content of cyclic adenosine monophosphate (determined by radioimmunoassays) of intact contracting trabeculae were studied. The lack of effect of the phosphodiesterase inhibitors in failing human hearts could not be explained by an altered phosphodiesterase inhibition, since the properties of the phosphodiesterase isoenzymes I–III and also the inhibitory effects of the phosphodiesterase inhibitors on these isoenzymes did not differ between failing and nonfailing human myocardial tissue. Instead, it may be due to a diminished formation of cyclic adenosine monophosphate in failing hearts, presumably caused mainly by a defect in receptor-adenylate cyclase coupling at least in idiopathic dilated cardiomyopathy. Both the basal and the pimobendan-stimulated or isoprenaline-stimulated contents of cyclic adenosine monophosphate of intact contracting trabeculae from failing hearts were decreased compared with the levels in nonfailing hearts. However, under the combined action of isoprenaline and pimobendan the cyclic adenosine monophosphate level reached values as high as with each compound alone in nonfailing preparations, and in addition the positive inotropic effect of isoprenaline was restored. These findings may have important clinical implications. Along with the elevated levels of circulating catecholamines the positive inotropic effects of the phosphodiesterase inhibitors may be maintained in patients with heart failure. Furthermore, the concomitant application of a β-adrenoceptor agonist and a phosphodiesterase inhibitor might be beneficial in terminal heart failure refractory to conventional therapeutic regimens.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00167387
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  • 7
    Electronic Resource
    Electronic Resource
    Stimulation of protein phosphatases as a mechanism of the muscarinic-receptor-mediated inhibition of cardiac L-type Ca2+ channels (1995)
    Springer
    Pflügers Archiv 429 (1995), S. 531-538 
    Details
    ISSN: 1432-2013
    Keywords: L-Type calcium channel ; Protein phosphatases ; Muscarinic effects ; Acetylcholine ; Iso-proterenol
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Acetylcholine decreases currents through cardiac L-type Ca2+ channels after stimulation with agents which elevate levels of cyclic adenosine monophosphate, such as isoproterenol, but there is still a controversy over the mechnisms of this muscarinic effect. We tested the hypothesis of whether, after isoproterenol stimulation, protein phosphatases are activated by acetylcholine. Whole-cell currents were recorded from guinea-pig ventricular myocytes. The effect of 10−5 M acetylcholine on currents induced by 10−8 M isoproterenol was studied in the absence or presence of protein phosphatase inhibitors. Three agents reduced the acetylcholine response: okadaic acid (3 or 9 · 10−6 M) and cantharidin (3 · 10−6 M) added to the pipette solution, and bath-applied fluoride (3 mM). In contrast, pipette application of other phosphatase inhibitors, namely the inhibitor PPI2 (1000 U/ml), ciclosporin (10−5 M), or calyculin A (10−6 M) did not significantly diminish the acetylcholine effect. Interestingly, there was no correlation between the effects of the compounds on basal Ca2+ current and their interference with the muscarinic response. An activation of type 2A phosphatases by acetylcholine would explain these findings. Indeed, okadaic acid is 3 orders of magnitude more potent in vitro in its inhibition of this isoform (purified from cardiac myocytes) than is calyculin A, while type-1 phosphatases are inhibited equally. The data support the attractive possibility that stimulation of protein phosphatases is part of the signal transduction cascade of Ca2+ channel inhibition by acetyl-choline.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00704158
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  • 8
    Electronic Resource
    Electronic Resource
    Protein phosphorylation in isolated trabeculae from nonfailing and failing human hearts (1996)
    Springer
    Molecular and cellular biochemistry 157 (1996), S. 171-179 
    Details
    ISSN: 1573-4919
    Keywords: human heart ; force of contraction ; protein phosphorylation ; phospholamban
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract Disturbances in the cAMP production during β-adrenergic stimulation and alterations of Ca 2+ transport controlling proteins and their regulation in the sarcoplasmic reticulum might be involved in the pathogenesis of the failing human heart. Thus, we investigated the cAMP-mediated phosphorylation of phospholamban, troponin I and C-protein in electrically driven, intact isolated trabeculae carneae from nonfailing and failing (NYHA IV) human hearts in parallel to contractile properties on the same tissue samples. The increase in force of contraction induced by isoproterenol (0.2 μM) or pimobendan (100 μM), a phosphodiesterase inhibitor, was diminished in the failing human hearts compared to nonfailing hearts by 49% and 36%, respectively. Concomitantly the isoproterenol-induced phosphorylation (pmol P/mg homogenate protein) of phospholamban, troponin I and C-protein was reduced from 13.0 ± 2.4 (n = 4), 30.5 ± 1.5 (n = 5) and 11.0 ± 1.3 (n = 5) in the nonfailing heart to 5.2 ±0.6 (n = 13), 14.6 ± 2.2 (n = 16) and 7.1 ± 1.0 (n = 6) in the failing human heart, respectively. Pimobendan changed the phosphorylation state of these proteins similar to isoproterenol. The fact that combined addition of both agents or dibuturyl CAMP (1 mM) alone restored the phosphorylation capacity as observed in the control groups indicates that i) a reduced cAMP generation is related to the reduced phosphorylation of regulatory phosphoproteins located in the sarcoplasmic reticulum and contractile apparatus e.g. phospholamban, troponin I and C-protein, that ii) there is a relationship between protein phosphorylation state and contractile activity and that iii) no changes in the respective content of phosphoproteins are involved in the limitation of cAMP-mediated inotopic activity in the failing human heart. (Mol Cell Biochem 157: 171–179, 1996)
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00227896
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  • 9
    Electronic Resource
    Electronic Resource
    Muscarinic-cholinoceptor mediated attenuation of phospholamban phosphorylation induced by inhibition of phosphodiesterase in ventricular cardiomyocytes: Evidence against a cAMP- dependent effect (1998)
    Springer
    Molecular and cellular biochemistry 187 (1998), S. 155-161 
    Details
    ISSN: 1573-4919
    Keywords: cardiomyocytes ; protein phosphorylation ; cAMP
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract In intact guinea pig ventricles, acetylcholine (ACH) has been shown to attenuate the positive inotropic effects of isobutylmethylxanthine (IBMX), a phosphodiesterase inhibitor, by reducing protein phosphorylation without altering cAMP levels. In the present study, we tested the hypothesis that the cAMP-independent inhibitory action of ACH is also evident in isolated cardiomyocytes. cAMP-dependent protein kinase (PKA) activity ratio (-cAMP/+cAMP) and phosphorylation of phospholamban (PLB) were determined in unlabeled and 32P-labeled guinea pig ventricular cardiomyocytes, respectively. IBMX increased PKA activity ratio and phosphorylation of PLB in a dose-dependent manner. When cardiomyocytes were incubated simultaneously with IBMX (0-1 mM) and ACH (2 μM), ACH attenuated PLB phosphorylation stimulated by low concentration (10-100 μM) but not by high concentrations (〉 200 μM) of IBMX. EC50 value for IBMX-induced phosphorylation of PLB was 32 ± 6 μM and increased nearly 3-fold after addition of ACH while PKA activity ratio remained unchanged. The rank order of cyclic nucleotide derivatives to phosphorylate PLB was 8 bromo-cAMP 〉 dibutyryl cAMP 〉 8 bromo-cGMP 〉 dibutyryl cGMP. ACH reduced phosphorylation of PLB stimulated by 8 bromo-cAMP. We conclude that in isolated cardiomyocytes (1) ACH inhibits phosphorylation of PLB stimulated by either IBMX or 8 bromo-cAMP and (2) ACH does not lower IBMX-stimulated PKA activity ratio. These effects of ACH on PLB phosphorylation cannot be explained by a reduction in IBMX-stimulated cAMP levels but may involve the activation of protein phosphatases.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006899931151
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