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.

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.

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.

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.

Constant-pressure perfusion of rat hindlimb shows alpha- and beta-adrenergic stimulation of oxygen consumption

1995 ◽  
Vol 269 (5) ◽  
pp. E960-E968 ◽  
Author(s):  
J. M. Ye ◽  
M. G. Clark ◽  
E. Q. Colquhoun
Keyword(s):  
Oxygen Consumption ◽  
Flow Rate ◽  
Constant Pressure ◽  
Constant Flow ◽  
Adrenergic Stimulation ◽  
Beta Adrenergic ◽  
Adrenergic Agents ◽  
Flow Perfusion ◽  
Stimulation Of

Isolated rat hindlimbs were perfused at 37 degrees C and constant physiological pressure (80 +/- 0.5 mmHg) while the flow rate that was allowed to freely self-adjust was monitored. Under these conditions, evidence was obtained for both alpha- and beta-adrenergic stimulation of oxygen consumption (VO2) in contrast to constant-flow perfusion, which has only convincingly shown alpha-adrenergic stimulation of VO2 in response to adrenergic agents. Addition of norepinephrine (NE; 1-33 nM) led to an increase in VO2 with a maximum of 29% above the basal value at 3.3 nM, even though the flow rate decreased. Phenylephrine (3.3-33 nM) and vasopressin (10-100 pM) also showed similar, but lesser in magnitude, vasoconstriction-associated stimulatory effects on VO2. Prazosin (an alpha 1-antagonist) completely reversed the NE-mediated decrease in flow rate and significantly blocked the increased VO2. In contrast, isoproterenol (10-1,000 nM) increased both flow rate (30%) and VO2 (32%). The isoproterenol-stimulated VO2 was not blocked by the beta 1-, beta 2-antagonist propranolol (10 microM), although the increased flow was reversed. In the presence of propranolol (1 or 10 microM), BRL-35135A (a beta 3-agonist) also stimulated VO2 (18%) without significant change in flow rate. These results lend further support to the role of the alpha 1-adrenoceptor in muscle VO2. In addition there is evidence for the presence of a functional beta 3-adrenoceptor as an additional subtype responsible for NE-mediated thermogenesis in the rat hindlimb.

beta-Adrenergic stimulation of respiratory ciliary activity

1980 ◽  
Vol 48 (5) ◽  
pp. 868-871 ◽  
Author(s):  
P. Verdugo ◽  
N. T. Johnson ◽  
P. Y. Tam
Keyword(s):  
Respiratory Epithelium ◽  
Ciliary Activity ◽  
Ciliated Cells ◽  
Adrenergic Stimulation ◽  
Laser Scattering ◽  
Beta Adrenergic ◽  
Ciliary Beating ◽  
Stimulation Of

We investigated the effect of isoproterenol on ciliary activity using a mucus-free preparation of cultured ciliated cells of the rabbit trachea. The frequency of ciliary beating was monitored by dynamic laser-scattering spectroscopy. The results demonstrated that isoproterenol directly stimulates the activity of ciliated cells of the respiratory epithelium and that this effect is beta-adrenergic specific inasmuch as the observed stimulation can be blocked by propranolol.

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