(Circulation. 2000;101:2625.)
© 2000 American Heart Association, Inc.
Basic Science Reports |
Rapid Electrical Stimulation of Contraction Reduces the Density of ß-Adrenergic Receptors and Responsiveness of Cultured Neonatal Rat Cardiomyocytes
Possible Involvement of Microtubule Disassembly Secondary to Mechanical Stress
From the Department of Laboratory Medicine (H.Y., M.N., M.I., T.S.) and Department of Internal Medicine I (S.Y., Y.T., N.T.), School of Medicine, Oita Medical University, Oita, Japan.
Correspondence to Hidetoshi Yonemochi, MD, Department of Laboratory Medicine, Oita Medical University, Idaigaoka 1-1, Hasama-machi, Oita 879-5593, Japan. E-mail yonemo{at}pios.oita-med.ac.jp
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Abstract |
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Background—Although tachycardia is commonly present in patients with congestive heart failure, its role in the development of congestive heart failure remains unclear. We studied the effect of rapid electrical stimulation of contraction on ß-adrenergic receptor (ß-AR) signal pathway in cultured cardiomyocytes of neonatal rats.
Methods and Results—Contraction of cardiomyocytes was induced by electrical stimulation at 50 V with twice the threshold pulse width. ß-ARs were identified by [3H]CGP-12177 and [3H]dihydroalprenolol. Electrical stimulation reduced cell-surface but not total ß-AR density; the effect was dependent on pacing frequency (a reduction of 11%, 28%, and 18% in cells paced at 2.5, 3.0, and 3.3 Hz, respectively). This reduction was apparent at 3 hours, in contrast to reduced ß-AR density after exposure to isoproterenol (ISP) for 1 hour. The fraction and inhibition constant of ß-AR binding agonist with high affinity were not affected by rapid electrical stimulation. In cardiomyocytes paced at 3.0 Hz for 24 hours, the response to ISP decreased compared with unpaced cells, 142% versus 204% of baseline with 1 µmol/L ISP, whereas the responses to forskolin or acetylcholine were not different. Treatment of cardiomyocytes with 2,3-butanedione monoxime (10 mmol/L) or taxol (10 µmol/L) inhibited the rapid pacing–induced reduction in ß-AR density.
Conclusions—Our results suggest that contractile activity is involved in regulation of cardiac function by modulating the ß-AR system independently of hemodynamic and neurohormonal factors. This may help to elucidate the role of mechanical stress in the development of heart failure.
Key Words: receptors, adrenergic, beta • electrical stimulation • contractility • heart failure • microtubule
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Introduction |
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Tachycardia-induced cardiomyopathy (TCM) has been widely used as a model to study the mechanism responsible for the onset and progression of congestive heart failure (CHF), because alterations in left ventricular function and the neurohormonal system are similar to those seen in patients with developing heart failure.1 2 3 4 Furthermore, tachycardia is one of the most common clinical syndromes seen in CHF patients. However, this symptom has been viewed only as a marker of sympathetic nervous tone, whereas its role in the development of CHF has received little attention.
Recent studies have demonstrated that treatment with ß-blockers fails to prevent the progression of cardiac dysfunction and neurohormonal activation in TCM.5 6 Furthermore, clinical CHF trials reporting on the effectiveness of ß-blockers generally show that improvement of cardiac pump function parallels reductions in resting heart rate.7 8 The beneficial cardiac effects of amiodarone in patients with cardiac dysfunction are dependent on basal heart rate and its reduction during treatment.9 These findings suggest that alterations in ß-adrenergic receptor (ß-AR) signal pathway noted in CHF patients might be attributable primarily to excessive mechanical load associated with increased contraction rate rather than ß-AR overstimulation by exposure to elevated catecholamines.
In the present study, we compared the effects of rapid electrical stimulation of contraction with those of isoproterenol (ISP) on the ß-AR system in cultured neonatal rat cardiomyocytes. Our model allows a direct assessment of the mechanical stress in the absence of neurohormonal and hemodynamic influences. The possible roles of microtubules and active tension generation in mediating the effects of rapid contraction on the ß-AR system were pharmacologically assessed by use of 2,3-butanedione monoxime (BDM) and taxol.
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Methods |
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Cell Culture
The experimental protocol was approved by the Ethics Review Committee for Animal Experimentation of Oita Medical University. Cardiac myocytes were prepared from 3- to 5-day-old Wistar rats, as described previously.10 11 Briefly, hearts removed under ether anesthesia were minced into 1-mm3 pieces in PBS. After treatment with 0.02% EDTA, the pieces were incubated in 5 mL of HBSS containing 2 mg/mL collagenase (type IV; Cooper Biochemical) for 10 minutes at 37°C, and then in 5 mL of Ca2+- and Mg2+-free HBSS containing 1000 IU/mL dispase (Godo Shusei) for 20 minutes at 37°C. The isolated cells were stored in DMEM, seeded in plastic culture dishes, and incubated at 37°C under 5% CO2 in air for 90 minutes to allow the attachment of fibroblasts to the bottom of dishes. Floating cardiomyocytes were then collected by decanting.
Cardiomyocytes were plated in 4-well culture trays at a concentration of 2x106 cells/well containing DMEM supplemented with 5% FBS (Gibco), 10 mmol/L HEPES, and kanamycin (100 IU). After 48 hours of culture, >70% of the cells adhered to the culture dishes and began to oscillate (beat spontaneously). Thereafter, the culture medium was changed daily. On day 4, most cardiomyocytes beat synchronously and at a constant frequency.
Electrical Stimulation
On day 4 of culture, cardiomyocytes were stimulated
at a high frequency by the method of Johnson et al,12 with
some modifications. An electronic stimulator (SEN-7203 Nihon Kohden)
was used to deliver square-wave electrical pulses at a constant voltage
of 50 V through the culture medium via platinum wires submersed at
opposite ends of each well of 4-well culture trays. The distance
between electrodes was 6.5 cm; therefore, the strength of the
electrical field was <8 V/cm, which is well below that reported to
cause cell injury.13 To minimize electrolysis at
electrodes and possible generation of oxidative species, the polarity
of the electrodes was altered with each electrical pulse, and 250
µmol/L ascorbic acid was added to the culture medium.14
To set the threshold pulse width at 50 V, the lowest pulse width
required for synchronous contraction in most cells was determined at
applied frequencies of 2.0 to 3.3 Hz, and then cells were stimulated at
twice this threshold. We discarded cardiomyocytes in which
the threshold pulse width was >1.5 ms.
To assess any additive effects of ISP on the reduced ß-AR density induced by rapid contraction, ISP was added to the culture medium during the final 3 hours of pacing.
Measurement of Cardiac ß-AR Density
As previously described,10 cardiac cell-surface
ß-ARs were identified by binding of the hydrophilic
radioligand [3H]CGP-12177 (specific
activity, 1.55 TBq/mmol; Amersham Pharmacia Biotech). Stimulated or
unstimulated cardiomyocytes cultured for 24 hours were
washed 3 times with assay buffer (0.25 mol/L sucrose, 10 mmol/L
MgCl2, and 50 mmol/L Tris-HCl [pH 7.4])
and incubated for 16 hours at 4°C with 2 mL of assay buffer
containing [3H]CGP-12177 at concentrations of
0.25 to 15 nmol/L. After 2 washings with assay buffer to remove free
[3H]CGP-12177, cells were lysed with 0.5 mol/L
NaOH, and then 5 mL of Aquasol-2 (New England Nuclear) was added. The
associated radioactivity was determined by scintillation spectroscopy.
All measurements were performed in duplicate. Total ß-AR density was
measured with [3H]dihydroalprenolol (DHA)
(specific activity, 3.52 TBq/mmol; Amersham Pharmacia Biotech) at
concentrations of 0.30 to 20 nmol/L, as described above. The maximal
number of binding sites (Bmax) and the
dissociation constant (Kd) were calculated
by Scatchard linear regression analysis, with
r>0.90 as a criterion for acceptability of the data.
Nonspecific binding was defined as binding in the presence of 10
µmol/L d,l-propranolol and was <20% of total
binding at 5 nmol/L [3H]CGP-12177 and <30% at
10 nmol/L [3H]DHA. The protein content of the
cells was measured by the biuret method.15
We also evaluated the frequency- and time-dependent effects of rapid pacing on ß-AR density and inhibitory effects of BDM and taxol on rapid pacing–induced reduction in ß-AR density in the presence of 10 nmol/L [3H]CGP-12177.
Agonist competition binding curves were constructed with 5 nmol/L [3H]CGP-12177 and ISP (10-10 to 5x10-4 mol/L) at 14 different concentrations. Binding data were analyzed by nonlinear regression with Graphpad PRISM (Graphpad Software, Inc), in which best fit, 1-site versus 2-site, was determined by the P value for the F test. When there was no significant difference in the fit to the 1-site or 2-site model, the data were adopted for the 2-site model.
Measurement of Response of Cultured Cardiomyocytes to ISP,
Acetylcholine, and Forskolin
As previously described,10 spontaneous beating of
cultured cardiomyocytes was measured. Paced and unpaced
cultured cells were exposed to agents after 2 washings with the culture
medium, and then spontaneous beating was monitored at 37°C for 15
minutes. Cardiomyocytes in each culture dish were exposed to a single
concentration of agents and then discarded. For comparison between
stimulated and unstimulated cardiomyocytes, responses to
agents were assessed by changes in the spontaneous beating
frequency.
Drugs and Solutions
BDM, taxol, forskolin, ISP, and acetylcholine were purchased
from Sigma Chemical Co. Forskolin was dissolved in 50% (vol/vol) DMSO.
BDM was dissolved in 50% (vol/vol) methanol. ISP, taxol, and
acetylcholine were dissolved in distilled water. The final
concentrations of DMSO (<0.1%) and methanol (<0.1%) had no effect
on the spontaneous beating and ß-AR density.
Statistical Analysis
Data are expressed as mean±SEM and were analyzed by 1-
or 2-way ANOVA and either Scheffé’s F test or
Fisher’s protected least significant difference. A level of
P<0.05 was considered statistically significant.
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Results |
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TopAbstractIntroductionMethodsResultsDiscussionReferences |
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Response of Paced Cardiomyocytes to ISP, Forskolin, and Acetylcholine
We investigated the effect of ISP, forskolin, and acetylcholine on the spontaneous beating of cultured cardiomyocytes either unpaced or paced at 3.0 Hz for 24 hours. The spontaneous beating frequency at baseline was high in paced cells compared with unpaced cells (114±5 versus 96±6 bpm; n=4 to 8, P<0.05). Although the response to ISP increased dose-dependently in both paced and unpaced cells, the beating frequency was significantly lower in paced cells treated with 0.1 and 1 µmol/L ISP than in unpaced cells (Figure 1
). In contrast,
subthreshold pacing did not affect the response of cultured cells to
ISP (data not shown).
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) and not paced (•). Cardiomyocytes were washed with
culture medium before exposure to various concentrations of ISP. Data
represent mean±SEM and are expressed as a percentage of
baseline values (n=6 to 10 from 4 separate cultures).
*P<0.01 vs baseline. 
P<0.01 vs
unpaced cells.The response to forskolin was the same in paced and unpaced cells (164±36% versus 171±15% of baseline at 10 µmol/L, n=5 and 6; 125±4% versus 146±12% at 1 µmol/L, n=4 and 5; and 113±9% versus 124±14% at 0.1 µmol/L, n=6 and 5). Treatment with 50 nmol/L acetylcholine reduced the spontaneous beating frequency of paced and unpaced cardiomyocytes (a reduction of 14±4% versus 15±5%, n=5). In cardiomyocytes treated with 0.1 µmol/L ISP, acetylcholine further decreased spontaneous beating frequency of paced cells (n=4) and unpaced cells (n=8) (a reduction of 16±4% versus 22±6% at 50 nmol/L and 63±22% versus 61±12% at 1 µmol/L). However, the response to acetylcholine was not different in paced and unpaced cells in either basal or ISP-stimulated conditions.
Effects of Rapid Electrical Stimulation of Contraction on ß-AR
Density and Morphology of Cultured Cardiomyocytes
To explore the mechanism of blunted response to ISP in
electrically stimulated cardiomyocytes, we measured
cell-surface ß-AR density in these cells.
Representative saturation curves for
[3H]CGP-12177 and Scatchard analysis of
the data indicated that binding of
[3H]CGP-12177 to cultured
cardiomyocytes was saturated at a concentration of 10
nmol/L and that the ligand interacted with a single class of binding
sites (Figure 2). Electrical stimulation
of cardiomyocytes at 3.0 Hz for 24 hours decreased
Bmax (109±9 versus 74±8 fmol/mg protein, n=4,
P<0.05) but had no effect on the affinity for the ligand
(3.1±0.4 versus 2.6±0.5 nmol/L, n=4). Therefore, subsequent
determinations of the cell-surface ß-AR density were performed in the
presence of 10 nmol/L [3H]CGP-12177. The effect
of pacing on cell-surface ß-AR density was frequency- and
time-dependent, as shown in Figures 3 and 4, respectively. A reduction by 29% of
cell-surface ß-AR density was apparent at 3 hours and reached a
plateau of 33% at 6 hours. Cell-surface ß-AR density in
cardiomyocytes paced at a subthreshold pulse width did not
differ from that of unpaced cells (105±4 fmol/mg protein, n=4, versus
108±3 fmol/mg protein, n=10). Total ß-AR density was not different
between paced and unpaced cardiomyocytes, as identified
with [3H]DHA (Bmax,
434±118 versus 410±137 fmol/mg protein;
Kd, 11±3 versus 12±3 nmol/L, n=4).
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ISP competed for binding sites with high-affinity and low-affinity
constants that were not different between paced and unpaced
cardiomyocytes (paced cells, 1.42±0.78 nmol/L, 1.3
µmol/L, n=5; unpaced cells, 1.92±0.58 nmol/L, 5.1±1.8
µmol/L, n=6). The proportion of ß-ARs showing high-affinity binding
for ISP was not different between paced and unpaced cells (23.4±11.2%
versus 26.3±3.9%, respectively). A representative
competitive inhibition agonist binding curve is shown in Figure 5.
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As shown in Figure 6, there were no gross
morphological differences between paced and unpaced
cardiomyocytes for 24 hours at 3 Hz as assessed by
phase-contrast microscopy.
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Mechanism of Reduced ß-AR Density Induced by Rapid Electrical
Stimulation of Contraction
We compared the effects of ISP and rapid electrical stimulation of
contraction on ß-AR density. As shown in Figure 7, exposure to 1 µmol/L ISP
reduced ß-AR density on unpaced cardiomyocytes
significantly, by 32% at 1 hour and 23% at 3 hours. In contrast, the
effect of pacing at 3.0 Hz on ß-AR density appeared only at 3 hours
but not at 1 hour. Exposure to 1 µmol/L ISP caused a further
decrease in ß-AR density on paced cells at 2.5 Hz but not at 3.0 Hz
for 24 hours (Figure 8). The duration of
ISP-induced increase in beating frequency was <1 hour (90±6 and
102±9 bpm at baseline and 45 minutes after exposure to ISP,
respectively, n=6), which was not long enough to increase ß-AR
density.
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Next, we investigated the effects of BDM and taxol on rapid
pacing–induced reduction in ß-ARs. Treatment of
cardiomyocytes with BDM at 10 mmol/L or taxol at
10 µmol/L abolished the effect of rapid pacing on ß-AR density
(unpaced, 99±5; paced, 82±3; paced+BDM, 106±4; paced+taxol, 100±1
fmol/mg protein), whereas they did not affect ß-AR density on unpaced
cardiomyocytes (Figure 9).
Furthermore, treatment with 10 µmol/L taxol had no effect on
spontaneous beating and did not interfere with electrical stimuli. In
the presence of 10 mmol/L BDM, the response to electrical stimuli
was diminished in some cardiomyocytes (<20%) paced for 24
hours in 1 of the 4 cultures, whereas spontaneous beating was not
affected in unpaced cells.
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Discussion |
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TopAbstractIntroductionMethodsResultsDiscussionReferences |
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We demonstrated in the present study that rapid electrical stimulation of contraction reduced cell-surface ß-AR density and the response of cultured neonatal rat cardiomyocytes to ISP. This is the first report that provides evidence for the direct involvement of contractile activity in the regulation of cardiac function by modulating the ß-AR system through microtubules, independent of hemodynamics and neurohormonal factors.
Rapid Pacing Reduces Cell-Surface ß-AR Density and Response
to ISP
The potential role of contractile activity in the development of
CHF has been underinvestigated, although tachycardia is one
of the most common clinical syndromes seen in CHF patients. Recently,
Spinale et al5 investigated the effects of ß-blockers on
cardiac function in TCM, which has been used as a heart failure model
with an alteration in the ß-AR signal pathway. They concluded that
modulation of chronotropy contributes to the beneficial cardiac effects
of ß-blockers during the progression of TCM. Levett et
al6 also showed that treatment with ß-blockers did not
prevent the progression of cardiac dysfunction and neurohormonal
activation in TCM. These findings suggest that alterations of the
ß-AR system noted in TCM might be attributed primarily to increased
contractile activity rather than ß-AR overstimulation by exposure to
elevated plasma catecholamines, which has been proposed as
a mechanism for the blunted ß-AR responsiveness.16 To
address this issue, using cultured cardiomyocytes, we
examined the effects of rapid stimulation of contraction on the ß-AR
system. This experimental setup allows the direct assessment of the
role of contractile activity in the absence of confounding factors,
such as neurohormonal and hemodynamic influences. In
the present study, cell-surface but not total ß-AR density and
the response of cardiomyocytes to ISP were diminished by
rapid electrical stimulation of contraction, as shown in Figures 1
, 3, and 4. In addition, although both rapid
pacing– and ISP-induced ß-AR stimulation reduced cell-surface ß-AR
density in cultured cardiomyocytes, the time courses of
their respective effects on ß-AR density obviously differed, and
their effects were in part additive, as shown in Figures 7 and 8. These results show that increased contractile activity
reduces cell-surface ß-AR density and diminishes the response to ISP
independently of neurohormonal and hemodynamic
influences.
In TCM, abnormalities in components downstream of ß-ARs, such as guanine nucleotide–binding regulatory (G) proteins and adenylyl cyclase activity, have been reported.1 In the present study, however, responses to forskolin and acetylcholine were not different between paced and unpaced cardiomyocytes when assessed by change of spontaneous beating frequency, a physiological end point. These results clearly indicated that G protein (Gs and Gi) levels and adenylyl cyclase activity were not markedly affected or involved in blunted response to ISP in cardiomyocytes paced at high frequency. Although competitive inhibition binding curves were performed here with [3H]CGP-12177, the values obtained, such as inhibition constants for ISP and the proportion of ß-ARs displaying high-affinity binding, were not significantly different from those of previous studies using 125I-labeled cyanopindolol or [3H]DHA in dogs, pigs, or calves.1 17 18 The present data obtained from these curves were not different between paced and unpaced cardiomyocytes, suggesting no change in coupling to Gs of ß-ARs reduced by rapid stimulation of contraction.
The present study was carefully designed to minimize the
confounding effects of oxidative species and nonspecific toxic effects
of the voltage on cultured cardiomyocytes, as described in
detail in the Methods section. Phase-contrast microscopy demonstrated
no significant differences in histological changes
between paced and unpaced cardiomyocytes (Figure 6).
Thus, it appears that the effects of rapid pacing on the ß-AR system
are associated with an increase in contractile activity rather than
cell damages by nonspecific effects exerted by electrical
stimulation.
Possible Involvement of Microtubules and Active Tension Generation
in Reduced ß-AR Density Induced by Rapid Pacing
The role of the cytoskeleton, including microtubules, in
contractile dysfunction has been shown in hypertrophied19
and failing myocardium in humans20 and in
TCM.21 In cultured neonatal rat
cardiomyocytes, there are 
2 reported mechanisms of
microtubular disassembly: one is Ca2+
overload,22 and the other is mechanical
stress.23 In the present study, the effect of rapid
pacing on ß-AR density was abolished by treatment with 10
µmol/L taxol, which hyperpolymerizes and stabilizes
microtubules.24 These results are consistent with
those of Palmer et al,25 who demonstrated that the
microtubule assembly and ß-AR responsiveness of isolated
cardiomyocytes were depressed in a rat model of cardiac
hypertrophy 30 weeks after aortic contraction and that
increased microtubule assembly by taxol partially recovered the
response to ISP. In the present study, the effect of rapid pacing
on ß-AR density was also inhibited by treatment with 10 mmol/L
BDM. This concentration of BDM is reported to effectively inhibit
actin-myosin crossbridge formation and thereby uncouple the electrical
and mechanical components of excitation-contraction coupling with
relatively little effect on peak concentration of intracellular free
Ca2+ of cardiomyocyte
transient.26 27 Therefore, the data obtained with BDM
suggest that the active tension generation during contraction
contributes to the rapid pacing–induced reduction in ß-AR density
and is probably more relevant for this process than the increase of
transient Ca2+ influxes. Of interest, this
finding contrasted well with the primary importance of elevated
cytosolic Ca2+ levels for microtubular disruption
by ß-AR activation.22 Furthermore, we showed previously
that microtubules regulate cell-surface ß-AR density in cultured
cardiomyocytes through their involvement in the receptor
recycling process,11 a finding supported by data from
other laboratories.28 29 Taken together, it is possible
that microtubule disassembly secondary to mechanical stress is involved
in reduced ß-AR density induced by rapid pacing via changes in the
receptor recycling process. However, the intracellular
Ca2+ level and the state of microtubule assembly
remain to be investigated in future studies.
Clinical Implications
Our results suggest that tachycardia noted in CHF
patients may be a relevant and independent component of the vicious
circle of heart failure. Therefore, if CHF patients have an
additional reversible component of cardiac dysfunction due to
tachycardia, heart rate reduction itself should contribute
to improved ventricular function or prevention of
progression of ventricular dysfunction. This may also
provide insight into the beneficial effects of ß-blockers and
amiodarone in CHF patients and the poor prognosis associated
with the basal heart rate in patients with
cardiovascular diseases.7 9 30 However,
care must be applied in extrapolating this relatively short-term study
in vitro to the pathogenesis of chronic heart failure in vivo.
In conclusion, the present results suggest that ß-AR downregulation induced by contractile activity might be one of the mechanisms underlying the onset and/or progression of heart failure. Accordingly, reduction of heart rate might represent an important component of treatment of CHF. Our findings also help to elucidate the role of mechanical stress in the development of heart failure.
Received September 7, 1999; revision received December 3, 1999; accepted December 22, 1999.
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References |
|---|
|
TopAbstractIntroductionMethodsResultsDiscussionReferences |
|---|
1. Kiuchi K, Shannon RP, Helmer GA, et al. Myocardial ß-adrenergic receptor function during the development of pacing induced heart failure. J Clin Invest. 1993;91:907–914.
2.
Cory CR, McCutcheon LJ, O’Grady M, et al.
Compensatory downregulation of myocardial Ca channel in SR from dogs
with heart failure. Am J Physiol. 1993;264:H926–H937.
3.
Armstrong PW, Stopps TP, Ford SE, et al. Rapid
ventricular pacing in the dog:
pathophysiological studies of heart failure.
Circulation. 1986;74:1075–1084.
4.
Wilson JR, Douglas P, Hickey WF, et al. Experimental
congestive heart failure produced by rapid ventricular
pacing in the dog: cardiac effects. Circulation. 1987;75:857–867.
5. Spinale FG, Johnson WS, Wang Y, et al. Direct effects of chronic beta-adrenergic receptor blockade of left ventricular and myocyte function in a model of tachycardia-induced congestive heart failure. J Cardiac Failure. 1996;2:311–318.[Medline] [Order article via Infotrieve]
6.
Levett JM, Marinelli CC, Lund DD, et al. Effects
of ß-blockade of neurohormonal responses and neurochemical
markers in pacing-induced heart failure. Am J Physiol. 1994;266:H468–H475.
7.
CIBIS Investigators and Committees. A randomized trial
of ß-blockade in heart failure: the Cardiac Insufficiency
Bisoprolol Study (CIBIS). Circulation. 1994;90:1765–1773.
8. Just H. Pathophysiological targets for beta-blocker therapy in congestive heart failure. Eur Heart J. 1996;17(suppl B):2–7.
9. Nul DR, Doval HC, Grancelli HO, et al, for GESICA-GEMA. Heart rate is a marker of amiodarone mortality reduction in severe heart failure. J Am Coll Cardiol. 1997;29:1199–1205.[Abstract]
10.
Yonemochi H, Yasunaga S, Teshima Y, et al. Mechanism
of ß-adrenergic receptor upregulation induced by ACE inhibition
in cultured neonatal rat cardiac myocytes: roles of bradykinin and
protein kinase C. Circulation. 1998;97:2268–2273.
11.
Yonemochi H, Saikawa T, Takakura T, et al. Effects of
calcium antagonists on ß-receptors of cultured
cardiac myocytes isolated from neonatal rat ventricle.
Circulation. 1990;81:1401–1408.
12.
Johnson TB, Kent RL, Bubolz BA, et al. Electrical
stimulation of contractile activity accelerates growth of cultured
neonatal cardiocytes. Circ Res. 1994;74:448–459.
13. Tovar O, Tung L. Electroporation and recovery of cardiac cell membrane with rectangular voltage pulses. Am J Physiol. 1992;32:H1128–H1136.
14. Mitchell RH, Bailey AH, Anderson JM, et al. Electrical stimulation of cultured myocardial cells. J Biomed Eng. 1992;14:52–56.[Medline] [Order article via Infotrieve]
15. Gornall AG, Bardawill CJ, David MM. Determination of serum proteins by means of the biuret reaction. J Biol Chem. 1948;177:751–766.
16.
Patel M, Stewart JM, Loud AV, et al. Altered function
and structure of the heart in dogs with chronic elevation in plasma
norepinephrine. Circulation. 1991;84:2091–2100.
17. Anzai T, Lai NC, Gao M, et al. Dissociation between regional dysfunction and ß-adrenergic receptor signaling in heart failure. Am J Physiol. 1998;275:H1267–H1273.
18.
Vatner DE, Young MA, Knight DR, et al.
ß-Receptors and adenylate cyclase: comparison of
nonischemic, ischemic, and postmortem tissue.
Am J Physiol. 1990;258:H140–H144.
19.
Tsutsui H, Ishihara K, Cooper G. Cytoskeletal role in
the contractile dysfunction of hypertrophied myocardium.
Science. 1993;260:682–687.
20.
Schaper J, Froede R, Hein St, et al. Impairment of
myocardial ultrastructure and changes of cytoskeleton in dilated
cardiomyopathy. Circulation. 1991;83:504–514.
21.
Eble D, Spinale FG. Contractile and cytoskeletal
content, structure, and mRNA levels with
tachycardia-induced cardiomyopathy.
Am J Physiol. 1995;268:H2426–H2439.
22.
Hori M, Sato H, Kitakaze M, et al. ß-Adrenergic
stimulation disassembles microtubules in neonatal rat cultured
cardiomyocytes through intracellular
Ca2+ overload. Circ Res. 1994;75:324–334.
23.
Watson PA, Hannan R, Carl LL, et al. Contractile
activity and passive stretch regulate tubulin mRNA and protein content
in cardiac myocytes. Am J Physiol. 1996;271:C684–C689.
24.
Tsutsui H, Tagawa H, Kent RL, et al. Role of
microtubules in contractile dysfunction of hypertrophied
cardiocytes. Circulation. 1994;90:533–555.
25. Palmer B, Valent S, Holder EL, et al. Microtubules modulate cardiomyocyte ß-adrenergic response in cardiac hypertrophy. Am J Physiol. 1998;275:H1707–H1716.
26. Blanchard EM, Smith GL, Allen DG, et al. The negative effects of 2,3-butanedione monoxime on initial heart, tension, and aequorin light output of ferret papillary muscle. Eur J Physiol. 1990;416:219–221.[Medline] [Order article via Infotrieve]
27. Kaye D, Pimental D, Prasad S, et al. Role of transiently altered sarcolemmal membrane permeability and basic fibroblast growth factor release in hypertrophic response of adult rat ventricular myocytes to increase mechanical activity in vitro. J Clin Invest. 1996;97:281–291.[Medline] [Order article via Infotrieve]
28. Limas CJ, Limas C. Effects of xamoterol on the reversible cycling of cardiac adrenoceptors. J Cardiovasc Pharmacol. 1990;16:945–951.[Medline] [Order article via Infotrieve]
29.
Marsh JD, Lachance D, Kim D. Mechanisms of
beta-adrenergic receptor regulation in cultured chick heart cells.
Circ Res. 1985;57:171–181.
30. Hjalmarson A, Gilpin EA, Kjekshus J, et al. Influence of heart rate on mortality after acute myocardial infarction. Am J Cardiol. 1990;65:547–553.[Medline] [Order article via Infotrieve]
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|
 |
|
 Y. Mizukami, A. Iwamatsu, T. Aki, M. Kimura, K. Nakamura, T. Nao, T. Okusa, M. Matsuzaki, K.-i. Yoshida, and S. Kobayashi ERK1/2 Regulates Intracellular ATP Levels through {alpha}-Enolase Expression in Cardiomyocytes Exposed to Ischemic Hypoxia and Reoxygenation J. Biol. Chem., November 26, 2004; 279(48): 50120 - 50131. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 N. Inoue, T. Ohkusa, T. Nao, J.-K. Lee, T. Matsumoto, Y. Hisamatsu, T. Satoh, M. Yano, K. Yasui, I. Kodama, et al. Rapid electrical stimulation of contraction modulates gap junction protein in neonatal rat cultured cardiomyocytes: Involvement of mitogen-activated protein kinases and effects of angiotensin ii-receptor antagonist J. Am. Coll. Cardiol., August 18, 2004; 44(4): 914 - 922. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
M. Ichinose, H. Yonemochi, T. Sato, and T. Saikawa Diazoxide triggers cardioprotection against apoptosis induced by oxidative stress Am J Physiol Heart Circ Physiol, June 1, 2003; 284(6): H2235 - H2241. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 M. Zaugg, M. C. Schaub, T. Pasch, and D. R. Spahn Modulation of {beta}-adrenergic receptor subtype activities in perioperative medicine: mechanisms and sites of action Br. J. Anaesth., January 1, 2002; 88(1): 101 - 123. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 C.-E. Laurent, R. Cardinal, G. Rousseau, M. Vermeulen, C. Bouchard, M. Wilkinson, J. A. Armour, and M. Bouvier Functional desensitization to isoproterenol without reducing cAMP production in canine failing cardiocytes Am J Physiol Regulatory Integrative Comp Physiol, February 1, 2001; 280(2): R355 - R364. [Abstract] [Full Text] [PDF]
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