Relation between contractile function and regulatory cardiac proteins in hypertrophied hearts

1996 ◽  
Vol 270 (6) ◽  
pp. H2021-H2028 ◽  
Author(s):  
B. Stein ◽  
S. Bartel ◽  
U. Kirchhefer ◽  
S. Kokott ◽  
E. G. Krause ◽  
...  
Keyword(s):  
Sarcoplasmic Reticulum ◽  
Troponin I ◽  
Contractile Function ◽  
Papillary Muscles ◽  
Camp Accumulation ◽  
Adrenergic Stimulation ◽  
Beta Adrenergic ◽  
C Protein ◽  
Camp Formation ◽  
Phosphate Incorporation

The aim of this study was to examine the mechanism(s) underlying the reduced isoproterenol-induced positive inotropic and lusitropic effects in hypertrophied hearts. Chronic beta-adrenergic stimulation (2.4 mg isoproterenol.kg-1. day-1 for 4 days) induced cardiac hypertrophy by 33 +/- 2% in rats. A parallel downregulation of phospholamban (PLB) and sarcoplasmic reticulum Ca2(+)-ATPase (SERCA2) protein expression by 49 and 40%, respectively, was observed, whereas troponin I (TNI) and C protein remained unchanged. In papillary muscles from chronically beta-adrenergically stimulated rats, the isoproterenol-induced positive inotropic and lusitropic effects, as well as adenosine 3',5'-cyclic monophosphate (cAMP) accumulation, were attenuated compared with those in control animals. Acute exposure to isoproterenol induced phosphate incorporation into PLB, TNI, and C protein of 48 +/- 4.6, 55 +/- 5.0, and 27 +/- 4.9 pmol/mg homogenate protein, respectively, in control animals. In the hypertrophied hearts, phosphate incorporation into PLB was reduced by 76%, whereas phosphate incorporation into TNI or C protein remained unchanged. In conclusion, chronic beta-adrenergic stimulation reduced the isoproterenol-stimulated positive inotropic and lusitropic effects in papillary muscles, which were accompanied by 1) diminished cAMP formation, 2) attenuation of cAMP-mediated PLB phosphorylation, and 3) downregulation of PLB and SERCA2 protein.

Intracellular mechanisms mediating reversal of beta-adrenergic stimulation in intact beating hearts

1993 ◽  
Vol 264 (3) ◽  
pp. H791-H797 ◽  
Author(s):  
L. Talosi ◽  
I. Edes ◽  
E. G. Kranias
Keyword(s):  
Sarcoplasmic Reticulum ◽  
Guinea Pig ◽  
Troponin I ◽  
Adrenergic Stimulation ◽  
Beta Adrenergic ◽  
Dependent Protein ◽  
Camp Levels ◽  
Isoproterenol Infusion ◽  
Phosphate Incorporation ◽  
Stimulation Of

The changes in 32P labeling of phosphoproteins were studied in Langendorff-perfused guinea pig hearts during reversal of the stimulatory effects of isoproterenol. Exposure of the hearts to isoproterenol was associated with significant increases in adenosine 3',5'-cyclic monophosphate (cAMP) levels and in the phosphate incorporation into phospholamban in sarcoplasmic reticulum, the 15-kDa protein in the sarcolemma, and troponin I in the myofibrils. Phospholamban was phosphorylated on serine and threonine residues, both of which are sites for cAMP-dependent and Ca(2+)-calmodulin-dependent protein kinases, respectively. Termination of isoproterenol infusion was associated with reversal of the mechanical effects of isoproterenol stimulation and reversal of the increases in tissue cAMP levels. However, the decreases in cAMP levels correlated only with dephosphorylation of phosphoserine in phospholamban. Dephosphorylation of phosphothreonine in phospholamban, the 15-kDa sarcolemmal protein, and troponin I occurred at a slower rate. These findings suggest that cAMP-dependent phosphorylation of phospholamban (phosphoserine) may play a prominent role during beta-adrenergic stimulation of intact hearts.

scholarly journals Phosphorylation of phospholipids in isolated guinea pig hearts stimulated with isoprenaline

1988 ◽  
Vol 251 (1) ◽  
pp. 189-194 ◽  
Author(s):  
G Jakab ◽  
S T Rapundalo ◽  
R J Solaro ◽  
E G Kranias
Keyword(s):  
Sarcoplasmic Reticulum ◽  
Guinea Pig ◽  
Total Phospholipid ◽  
Fold Increase ◽  
Adrenergic Stimulation ◽  
Beta Adrenergic ◽  
Adrenergic Agents ◽  
32P Incorporation ◽  
Phosphate Incorporation ◽  
Stimulation Of

Phosphorylation of phospholipids was studied in Langendorff perfused guinea pig hearts subjected to beta-adrenergic stimulation. Hearts were perfused with Krebs-Henseleit buffer containing [32P]Pi and freeze-clamped in a control condition or at the peak of the inotropic response to isoprenaline. 32P incorporation into total phospholipids, individual phospholipids and polyphosphoinositides was analysed in whole tissue homogenates and membranes, enriched in sarcoplasmic reticulum, prepared from the same hearts. Isoprenaline stimulation of the hearts did not result in any significant changes in the levels of phosphate incorporation in the total phospholipid present in cardiac homogenates (11.6 +/- 0.4 nmol of 32P/g for control hearts and 12.4 +/- 0.5 nmol of 32P/g for isoprenaline-treated hearts; n = 6), although there was a significant increase in the degree of phospholipid phosphorylation in sarcoplasmic reticulum (3.5 +/- 0.3 nmol of 32P/mg for control hearts and 6.7 +/- 0.2 nmol of 32P/mg for isoprenaline-treated hearts; n = 6). Analysis of 32P incorporation into individual phospholipids and polyphosphoinositides revealed that isoprenaline stimulation of the hearts was associated with a 2-3-fold increase in the degree of phosphorylation of phosphatidylinositol monophosphate and bisphosphate as well as phosphatidic acid in both cardiac homogenates and sarcoplasmic reticulum membranes. In addition, there was increased phosphate incorporation into phosphatidylinositol in sarcoplasmic reticulum membranes. Thus, perfusion of guinea pig hearts with isoprenaline is associated with increased formation of polyphosphoinositides and these phospholipids may be involved, at least in part, in mediating the effects of beta-adrenergic agents in the mammalian heart.

beta-Adrenergic regulation of cAMP and protein phosphorylation in phospholamban-knockout mouse hearts

1997 ◽  
Vol 272 (2) ◽  
pp. H785-H790 ◽  
Author(s):  
E. Kiss ◽  
I. Edes ◽  
Y. Sato ◽  
W. Luo ◽  
S. B. Liggett ◽  
...  
Keyword(s):  
Protein Phosphorylation ◽  
Troponin I ◽  
Signal Transduction Pathway ◽  
Microsomal Protein ◽  
Mouse Heart ◽  
Wild Type ◽  
Adrenergic Stimulation ◽  
Beta Adrenergic ◽  
C Protein ◽  
Camp Levels

The stimulatory effects of beta-adrenergic agonists reflect increases in intracellular adenosine 3',5'-cyclic monophosphate (cAMP) levels and phosphorylation of key regulatory proteins in the heart. One of these phosphoproteins is phospholamban (PLB) in sarcoplasmic reticulum, and ablation of PLB is associated with attenuation of the contractile responses to beta-adrenergic stimulation in the mouse heart. To determine whether this attenuation of beta-stimulation is due to altered phosphorylation characteristics of the other key cardiac phosphoproteins and/or to compensatory responses occurring in the absence of PLB, PLB-knockout and wild-type hearts were perfused and their protein phosphorylation patterns examined. The beta-adrenergic receptor density, adenylyl cyclase activity, tissue cAMP levels, and the basal phosphoprotein pattern were similar between PLB-knockout and wild-type hearts. Isoproterenol perfusion resulted in similar increases in the tissue cAMP levels and the degree of phosphorylation of troponin I, C protein, and the 21-kDa microsomal protein in wild-type and PLB-knockout hearts. These findings indicate that the attenuation of isoproterenol-mediated increases in contractility of the PLB-knockout hearts is not due to alterations in the beta-adrenergic signal transduction pathway or the degree of phosphorylation of the key cardiac regulatory phosphoproteins in myofibrils and sarcolemma.

scholarly journals Computational modeling of Takotsubo cardiomyopathy: effect of spatially varying β-adrenergic stimulation in the rat left ventricle

2014 ◽  
Vol 307 (10) ◽  
pp. H1487-H1496 ◽  
Author(s):  
Sander Land ◽  
Steven A. Niederer ◽  
William E. Louch ◽  
Åsmund T. Røe ◽  
Jan Magnus Aronsen ◽  
...  
Keyword(s):  
Left Ventricle ◽  
Takotsubo Cardiomyopathy ◽  
Troponin I ◽  
Contractile Function ◽  
Single Cells ◽  
Apical Ballooning ◽  
Calcium Sensitivity ◽  
Takotsubo Syndrome ◽  
Adrenergic Stimulation ◽  
Inotropic Effects

In Takotsubo cardiomyopathy, the left ventricle shows apical ballooning combined with basal hypercontractility. Both clinical observations in humans and recent experimental work on isolated rat ventricular myocytes suggest the dominant mechanisms of this syndrome are related to acute catecholamine overload. However, relating observed differences in single cells to the capacity of such alterations to result in the extreme changes in ventricular shape seen in Takotsubo syndrome is difficult. By using a computational model of the rat left ventricle, we investigate which mechanisms can give rise to the typical shape of the ventricle observed in this syndrome. Three potential dominant mechanisms related to effects of β-adrenergic stimulation were considered: apical-basal variation of calcium transients due to differences in L-type and sarco(endo)plasmic reticulum Ca2+-ATPase activation, apical-basal variation of calcium sensitivity due to differences in troponin I phosphorylation, and apical-basal variation in maximal active tension due to, e.g., the negative inotropic effects of p38 MAPK. Furthermore, we investigated the interaction of these spatial variations in the presence of a failing Frank-Starling mechanism. We conclude that a large portion of the apex needs to be affected by severe changes in calcium regulation or contractile function to result in apical ballooning, and smooth linear variation from apex to base is unlikely to result in the typical ventricular shape observed in this syndrome. A failing Frank-Starling mechanism significantly increases apical ballooning at end systole and may be an important additional factor underpinning Takotsubo syndrome.

Inotropic sensitivity to beta-adrenergic stimulation in early sepsis

1988 ◽  
Vol 255 (4) ◽  
pp. H699-H703 ◽  
Author(s):  
L. W. Smith ◽  
K. H. McDonough
Keyword(s):  
Contractile Function ◽  
Plasma Catecholamines ◽  
Left Ventricular ◽  
Adrenergic Stimulation ◽  
Maximal Increase ◽  
Beta Adrenergic ◽  
Arterial Blood ◽  
Myocardial Contractile ◽  
Early Sepsis

In early sepsis, maintenance of in vivo cardiovascular performance is at least partly dependent on sympathetic support to hearts with intrinsic contractile defects. Yet prolonged sympathetic stimulation, as occurs in sepsis, would be expected to alter the heart's ability to respond to this stimulation. We have investigated myocardial inotropic sensitivity to beta-adrenergic stimulation in a model of sepsis in which animals, at the time studied, exhibited bacteremia, normal arterial blood pressure and cardiac output, elevated heart rate, and elevated plasma catecholamines. Intrinsic myocardial contractile function, as assessed by the maximal rate of left ventricular pressure development (LV dP/dtmax) in an isovolumically contracting heart preparation, was significantly depressed in septic animals. To determine whether hearts from septic animals could respond normally to beta-adrenergic stimulation, we studied inotropic response to a bolus of isoproterenol in these isolated hearts. With maximal isoproterenol stimulation, hearts from septic animals were able to attain the same dP/dtmax as were hearts from control animals. With lower levels of isoproterenol, there was also no difference in inotropic indexes between the two groups when response was expressed as a percent of the maximal increase in dP/dtmax achieved with isoproterenol. These results suggest that in early sepsis, despite intrinsic myocardial contractile dysfunction, the ability of the heart to modulate its inotropic state in response in beta-adrenergic stimulation is intact.

Troponin I phosphorylation in spontaneously hypertensive rat heart: effect of beta-adrenergic stimulation

1997 ◽  
Vol 273 (3) ◽  
pp. H1440-H1451 ◽  
Author(s):  
B. K. McConnell ◽  
C. S. Moravec ◽  
I. Morano ◽  
M. Bond
Keyword(s):  
Troponin I ◽  
Ventricular Myocytes ◽  
Spontaneously Hypertensive Rat ◽  
Left Ventricular ◽  
Adrenergic Stimulation ◽  
Beta Adrenergic ◽  
Spontaneously Hypertensive ◽  
Myosin Light Chain 2 ◽  
Wistar Kyoto ◽  
Phospholamban Phosphorylation

We compared baseline and protein kinase A (PKA)-dependent troponin I (TnI) phosphorylation in 32Pi-labeled left ventricular myocytes from hearts of 26-wk spontaneously hypertensive rats (SHR) and Wistar-Kyoto controls (WKY). TnI phosphorylation was normalized to myosin light chain 2 phosphorylation, which was invariant. There was no difference in baseline TnI phosphorylation in SHR and WKY, but stimulation with isoproterenol, norepinephrine plus prazosin, forskolin, chloroadenosine 3',5'-cyclic monophosphate, or 3-isobutyl-1-methylxanthine caused a greater increase in TnI phosphorylation in the SHR than in the WKY. This was observed both in the presence and absence of the phosphatase inhibitor calyculin A; thus the differences in TnI phosphorylation between SHR and WKY are not due to decreased phosphatase activity in the SHR. After stimulation of the beta-adrenergic pathway, phospholamban phosphorylation was not different in SHR and WKY, indicating that the observed differences may be specific for PKA phosphorylation of TnI. The increased PKA-dependent TnI phosphorylation in the SHR resulted in decreased Ca2+ sensitivity of actomyosin adenosinetriphosphatase activity as compared with the WKY. We conclude that increased PKA-dependent TnI phosphorylation in the SHR may contribute to the impaired response to sympathetic stimulation.

scholarly journals On the mechanism of the reduction by thyroid hormone of β-adrenergic relaxation rate stimulation in rat heart

1989 ◽  
Vol 259 (1) ◽  
pp. 229-236 ◽  
Author(s):  
R E Beekman ◽  
C van Hardeveld ◽  
W S Simonides
Keyword(s):  
Thyroid Hormone ◽  
Protein Kinase ◽  
Sarcoplasmic Reticulum ◽  
Cyclic Amp ◽  
Relaxation Rate ◽  
Cardiac Tissue ◽  
Fold Increase ◽  
Protein Kinase Activity ◽  
Adrenergic Stimulation ◽  
Beta Adrenergic

The effects of beta-adrenergic stimulation on the relaxation rate and the Ca2+-transport rate in sarcoplasmic reticulum of hypothyroid, euthyroid and hyperthyroid rat hearts were studied. Administration of isoproterenol (0.1 microM) to perfused, electrically stimulated hearts (5 Hz) caused a decrease in the half-time of relaxation (RT 1/2) the extent of which depended on the thyroid status, i.e. hypothyroid (-24%), euthyroid (-19%) or hyperthyroid (-8%). A similar decreasing effect was found for the stimulation of Ca2+ transport in isolated SR by cyclic AMP and protein kinase, i.e. hypothyroid (75%), euthyroid (37%) and hyperthyroid (20%). These alterations were not due to differences in endogenous protein kinase activity or cyclic AMP production. Estimations of Ca2+-ATPase and phospholamban (PL) content of the sarcoplasmic reticulum were obtained by measurement of the phosphorylated forms of Ca2+-ATPase (E-P) and phospholamban (PL-P) followed by electrophoresis and autoradiography. A 3-fold decrease of PL-P, accompanied by a 2-fold increase of E-P per mg of protein was observed in sarcoplasmic reticulum preparations in the direction hypothyroid----hyperthyroid. Consequently the E-P/PL-P ratio increased from 0.32 (hypothyroid), through 0.81 (euthyroid) to 1.69 (hyperthyroid). In spite of certain limitations inherent to quantification of Ca2+-ATPase and phospholamban by their phosphorylated products, these data provide strong evidence that during thyroid-hormone mediated cardiac hypertrophy, with concomitant proliferation of the sarcoplasmic reticulum, the relative amount of phospholamban decreases with respect to Ca2+-ATPase. This could provide an explanation for the observed gradual diminishment of the beta-adrenergic effect on the relaxation rate when cardiac tissue is exposed to increasing amounts of thyroid hormone.

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