This Article Abstract Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Request Permissions Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Tajima, M. Articles by Lorell, B. H. Search for Related Content PubMed PubMed Citation Articles by Tajima, M. Articles by Lorell, B. H. Pubmed/NCBI databases Compound via MeSH Substance via MeSH Hazardous Substances DB CALCIUM COMPOUNDS CALCIUM, ELEMENTAL Medline Plus Health Information Heart Attack Heart Failure Related Collections Contractile function Gene expression Mechanism of atherosclerosis/growth factors

(Circulation. 1999;99:127-134.)
© 1999 American Heart Association, Inc.

Basic Science Reports

Treatment With Growth Hormone Enhances Contractile Reserve and Intracellular Calcium Transients in Myocytes From Rats With Postinfarction Heart Failure

Minori Tajima, MD, PhD; Ellen O. Weinberg, PhD; Jozef Bartunek, MD; Hongkui Jin, MD; Renhui Yang, MD; Nicholas F. Paoni, PhD; Beverly H. Lorell, MD

From the Charles A. Dana Research Institute, the Harvard-Thorndike Laboratory, and the Department of Medicine (Cardiovascular Division), Beth Israel Deaconess Medical Center, and Harvard Medical School, Boston, Mass (M.T., E.O.W., J.B., B.H.L.), and the Department of Cardiovascular Research, Genentech, Inc (H.J., R.Y., N.F.P.), South San Francisco, Calif.

Correspondence to Beverly H. Lorell, MD, Cardiovascular Division, Beth Israel Deaconess Medical Center, 330 Brookline Ave, Boston, MA 02215. E-mail blorell{at}bidmc.harvard.edu

	Abstract

Top Abstract Introduction Growth Hormone Effects in... Effects of Growth Hormone... Methods Results Discussion References

 
Background—Recombinant human growth hormone (GH) improves in vivo cardiac function in rats with postinfarction heart failure (MI). We examined the effects of growth hormone (14 days of 3.5 mg · kg^-1 · d^-1 begun 4 weeks after MI) on contractile reserve in left ventricular myocytes from rats with chronic postinfarction heart failure.

Methods and Results—Cell shortening and [Ca²⁺]_i were measured with the indicator fluo 3 in myocytes from MI, MI+GH, control, and normal animals treated with GH (C+GH) under stimulation at 0.5 Hz at 37°C. Cell length was similar in MI and MI+GH rats (150±5 and 157±5 µm) and was greater in these groups than in the control and C+GH groups (140±4 and 139±4 µm, P<0.05). At baseline perfusate calcium of 1.2 mmol/L, myocyte fractional shortening and [Ca²⁺]_i transients were similar among the 4 groups. We then assessed contractile reserve by measuring the increase in myocyte fractional shortening in the presence of high-perfusate calcium of 3.5 mmol/L. In the control and C+GH groups, myocyte fractional shortening and peak systolic [Ca²⁺]_i were similarly increased in the presence of high-perfusate calcium. In the presence of high-perfusate calcium, both myocyte fractional shortening and peak systolic [Ca²⁺]_i were depressed in the MI compared with the control groups. In contrast, myocyte fractional shortening (14.1±.9% versus 11.1±.9%, P<0.05) and peak systolic [Ca²⁺]_i (647±43 versus 509±37 nmol/L, P<0.05) were significantly higher in MI+GH than in MI rats and were comparable to controls. Left ventricular myocyte expression of sarcoplasmic reticulum Ca²⁺ ATPase 2 (SERCA-2) and left ventricular SERCA-2 protein levels were increased in MI+GH compared with MI rats.

Conclusions—Calcium-dependent contractile reserve is depressed in myocytes from rats with postinfarction heart failure. Long-term growth hormone therapy increases contractile reserve by restoring normal augmentation of systolic [Ca²⁺]_i in myocytes from rats with postinfarction heart failure.

Key Words: growth hormone • myocardial infarction • myocytes • calcium • heart failure

	Introduction

Top Abstract Introduction Growth Hormone Effects in... Effects of Growth Hormone... Methods Results Discussion References

 
Growth hormone administration in growth-hormone–deficient states and excess secretion in acromegaly produce a hyperkinetic state with enlargement (hypertrophy) of the heart and other organs that is associated with augmentation of circulating plasma volume, a reduction in systemic vascular resistance, elevation of cardiac output, and changes in glucose metabolism.^{1 2 3 4 5 6} These effects may be mediated in part by the vasodilator peptide insulin-like growth factor-1 (IGF-1),^{7 8} which promotes cardiac protein synthesis and expression of cardiac-restricted genes.^{9 10} Variably, growth hormone hypersecretion in acromegalic adults can result in a transition from a hyperkinetic state to overt heart failure with the phenotype of a dilated cardiomyopathy.¹¹ The actions of growth hormone and IGF-1 on cardiac performance in normal animals simulate human acromegaly and promote changes in isolated muscle contractility.^{12 13 14 15}

	Growth Hormone Effects in Failing Hearts

Top Abstract Introduction Growth Hormone Effects in... Effects of Growth Hormone... Methods Results Discussion References

 
The administration of growth hormone to patients with idiopathic dilated cardiomyopathy was associated with hypertrophic remodeling of the dilated, thin-walled hearts and an increase in cardiac output relative to myocardial oxygen consumption.¹⁶ When growth hormone was administered immediately after coronary ligation in rats, 3-week treatment in comparison with no therapy was associated with an increase in body weight, concentric hypertrophy, and better preservation of cardiac output associated with a decrease in systemic vascular resistance.¹⁷ Treatment with growth hormone early after experimental coronary ligation also preserved collagen matrix and reduced aneurysm formation,¹⁸ although this favorable effect was not observed when growth hormone was administered together with ß-adrenergic blockers.¹⁹ The benefits of the induction of mild concentric hypertrophy early after experimental infarction with regard to retarding left ventricular dilatation and improving systolic function have also been clearly demonstrated by Litwin et al²⁰ in response to a different growth-promoting agent, 2-tetradecylglycidic acid.

	Effects of Growth Hormone in Postinfarction Failure

Top Abstract Introduction Growth Hormone Effects in... Effects of Growth Hormone... Methods Results Discussion References

 
The effects of growth hormone and IGF-1 administration on contractile performance later after experimental infarction are controversial. Duerr et al²¹ administered IGF-1 plus growth hormone to rats for 4 weeks beginning 4 weeks after infarction, which stimulated body growth with minor changes in left ventricular remodeling, decreased systemic vascular resistance, and increased cardiac output compared with no treatment. Yang et al²² administered growth hormone for 15 days to rats beginning 4 weeks after coronary ligation and observed an increase in cardiac index and dP/dt and reduction in systemic vascular resistance in the absence of an increase in the ratio of left ventricular weight to body weight. Subsequently, Jin et al²³ administered growth hormone plus IGF-1 for 2 weeks beginning 3 months after infarction, in the presence or absence of captopril that was begun early after coronary ligation. In this study, the increases in cardiac index and stroke volume were significantly greater in animals treated with growth hormone plus IGF-1 than in animals treated with captopril alone, which implies an effect on myocardial contractility independent of changes mediated by systemic vasodilation.

We hypothesized that growth hormone therapy may directly increase contractile function in myocytes from rats after infarction. Growth hormone was administered at a dose and a duration that were insufficient to promote an increase in left ventricular mass. To examine contractile reserve, we measured isolated cell shortening and [Ca²⁺]_i by use of the fluorescence indicator fluo 3 in response to the elevation of extracellular calcium. We observed that growth hormone improved contractile reserve and increased the intracellular calcium transient in myocytes from rats with postinfarction heart failure.

	Methods

Top Abstract Introduction Growth Hormone Effects in... Effects of Growth Hormone... Methods Results Discussion References

 
Animal Model
Male Sprague-Dawley rats 8 weeks of age were obtained from Charles River Breeding Laboratories, Hollister, Calif. Myocardial infarction (MI) was produced by left coronary artery ligation, as described previously.²³ Sham-operated control animals underwent the same procedure, except that the suture was passed under the coronary artery and then removed. Four weeks after surgery, rats of the control (C) and MI cohorts were randomized into recombinant human growth hormone (GH)–treated and nontreated groups (C+GH, control, MI+GH, and MI). Growth hormone (Genentech, Inc) was injected subcutaneously (3.5 mg · kg^-1 · d^-1 for 14 days). Six weeks after surgery, including 14 days of treatment with growth hormone or vehicle, closed-chest in vivo left ventricular pressure was measured, as described by our laboratory.²⁴

Simultaneous Measurement of [Ca²⁺]_i and Cell Motion
The animals were then euthanized, and left ventricular myocytes were prepared with use of collagenase perfusion by a modification of the methods of Capogrossi et al,²⁵ as reported from our laboratory.^{26 27 28 29} After the collagenase perfusion and before myocyte dissociation, the well-defined scar and its colorless margin were excised from the left ventricle. Fifty microliters of 88.5 mmol/L fluo 3-AM in DMSO was added to 450 µL of fetal calf serum containing 0.05% pluronic F-127 (Molecular Probes, Inc), sonicated, and stored at -80°C. Myocytes were attached on coverslips with cell adhesive (Cell-Tak, Collaborative Research, Inc) and loaded with 1 µmol/L fluo 3^{30 31 32} (Molecular Probes, Inc) at room temperature for 20 minutes. Probenecid (0.5 mmol/L) was present in every solution to address the formal possibility of loss of fluo 3 via the anion transporter, which has been reported in measurement of [Ca²⁺]_i in some cell types.³³ The coverslip was washed and placed in a flow-through heated (37°C) cell superfusion chamber on the stage of an inverted microscope (Nikon). The excitation source was a high-pressure mercury arc lamp. With the interference filter, the excitation wavelength was 480±20 nm. The excitation beam was chopped at 360 Hz to reduce bleaching, and the myocyte was illuminated via epifluorescent optics with a Fluor x40 dry lens with correction collar (magnification, x40; numerical aperture, 0.85; working distance, 0.37 mm; focal length, 4.20 mm; Nikon Inc). The emission light was collected by the objective lens filtered by 535±25 nm and transmitted to a custom-modified photomultiplier spectrofluorometer system (FM-1000, Rincon Scientific Instruments). At the beginning of each experiment, myocyte autofluorescence was measured with 4 to 6 unloaded myocytes. An adjustable iris was used to restrict the optical image to only 1 myocyte of interest in each experiment to minimize fluorescence from other myocytes. The image of the beating myocyte was obtained by illumination via the 50-W standard microscope light source passed through a 640-nm band-pass filter. Myocyte motion was monitored with a solid-state camera (GP-CD60, Panasonic) and measured with a video detector system³⁴ (Crescent Electronics). The analog output signals of cell motion and the fluorescent transient were monitored and recorded continuously. Myocytes were stimulated at 0.5 Hz with 3-ms pulses. Myocyte fractional shortening was stable during 20 minutes of observation (106±6% of baseline in control cells and 96±3% in cells from postinfarction hearts, n=3 in each group, P=NS). There was also no decrease in fractional cell shortening before and after fluo 3 loading in myocytes from control and postinfarction hearts (n=3 per group; data not shown). To estimate calibrated levels of the [Ca²⁺]_i transients, immediately after each experiment the myocyte was superfused with the same buffer supplemented with 30 mmol/L 2,3-butanedione monoxime and 10 µmol/L calcium ionophore ionomycin in the presence of 1 mmol/L calcium. Then a 1-mol/L MnCl₂ stock solution was added to the buffer to yield a final concentration of 10 mmol/L. The cell was abruptly superfused with Mn²⁺ for saturation of fluo 3. After measurement of the mean value of the autofluorescence (F_BKG) and the fluorescence intensity with Mn²⁺ (F_Mn), the values of Fmax, Fmin, and estimated [Ca²⁺]_i were calculated as follows with the calibration method of Kao et al,³² as described elsewhere³⁵:

where K_d is the dissociation constant at 37°C for fluo 3 and is taken as 864 nmol/L.³¹ The fluorescence intensity of fluo 3 saturated with Mn²⁺ is 20% of that saturated with Ca²⁺, whereas the fluorescence intensity of Ca²⁺-free fluo 3 is 1/40 that of the Ca²⁺-bound form.³² With this approach, basal calibrated systolic and diastolic [Ca²⁺]_i levels are similar to values we have extensively reported in adult rat myocytes at stimulation rates of 0.5 Hz and at 37°C with use of the fluorescence indicator indo 1.^{26 27 28 29}

The yields of viable myocytes, which were defined as the percentage of rod-shaped myocytes paced at 0.5 Hz with clear striations and exclusion of trypan blue, were 60% to 70% in the control myocytes and 40% to 60% in myocytes from postinfarction hearts. One to 4 experiments were performed in sequence from separate coverslips of myocytes isolated from 1 heart (MI, n=10 hearts; M+GH, n=10 hearts; control, n=7 hearts; and C+GH, n=6 hearts).

Experimental Protocol
The myocytes from the control, C+GH, MI, and MI+GH groups were superfused with oxygenated HEPES-buffered solution of the following composition (mmol/L): NaCl 137, KCl 3.7, MgCl₂ 0.5, HEPES (free acid) 4.0, CaCl₂ 1.2, glucose 5.6, and probenecid 0.5, with a final pH of 7.40. The myocytes were paced at 0.5 Hz at 37°C. To assess calcium-dependent contractile reserve, myocyte fractional shortening was then measured in the presence of 3.5 mmol/L CaCl_2. The signals of cell motion and the [Ca²⁺]_i transients were recorded simultaneously in a steady state after 4 to 5 minutes of superfusion at each perfusate calcium concentration.

Analysis of LV Myocyte mRNA Levels
Immediately after isolated left ventricular myocytes were prepared as described above, half of the myocyte cell suspension was used for total RNA extraction with Tri Reagent (Sigma). Left ventricular myocyte RNA was extracted from control (n=6), MI (n=9), and MI+GH (n=10) hearts. The concentration of RNA in each sample was assessed spectrophotometrically. For the Northern blot analyses, 20 µg of total RNA from individual LV myocyte samples was size fractionated by electrophoresis in a 1.5% agarose-formaldehyde gel and transferred to a nitrocellulose membrane (Stratagene) by pressure transfer (Posiblot Pressure Blotter, Stratagene). The membrane was prehybridized for 10 minutes and hybridized sequentially with specific probes for 1 hour in QuikHyb hybridization solution (Stratagene) at 65°C. After hybridization, the membrane was washed in various concentrations of sodium chloride/sodium citrate buffer and SDS and exposed to Kodak MR film for 6 hours to 3 days at -80°C. The relative amounts of each mRNA were determined by densitometric analysis (Molecular Dynamics) and normalized to GAPDH. Stripping of the membrane for reuse was performed according to the manufacturer's instructions (Stratagene), and adequacy of stripping was verified by 2-day exposure of the membrane to film. Probes used were the cDNA fragment encoding the SR calcium ATPase (SERCA-2, provided by D. MacLennan), a 20-bp oligonucleotide encoding ß-myosin heavy chain, the cDNA fragment encoding rat GAPDH, and an 84-bp synthetic oligonucleotide complementary to the coding region of rat ANF. The cDNA fragments were radiolabeled with [-³²P]dCTP (New England Nuclear) with use of random priming (Boehringer Mannheim), and the oligonucleotides were radiolabeled with [-³²P]ATP with T4 polynucleotide kinase.

Western Blot Analysis of SERCA-2 Protein Levels
In the additional rats (control, n=6; MI, n=8; MI+GH, n=8), the hearts were excised, and infarct and noninfarct areas were separated to calculate percentage of the infarct area. The noninfarct left ventricular tissue was frozen in liquid nitrogen and stored at -80°C until use. Western blotting was performed by the method of Qi et al,³⁶ with slight modification. Briefly, tissue was homogenized in 9 vol of 150 mmol/L NaCl, and equal amounts of total protein (40 µg/lane) were separated on 7.5% SDS–polyacrylamide gel. Separated proteins were transferred to nitrocellulose membrane (Amersham Life Science). Blots were blocked with 2% (wt/vol) nonfat milk for 1 hour and then incubated with anti-mouse SERCA-2 ATPase monoclonal antibody (1:1000, Affinity Bioreagents, Inc) at 4°C overnight. After washing, the blots were incubated with horseradish peroxidase–conjugated goat anti-mouse antibody (1:1000, Amersham Life Science) for 1 hour. The blots were developed with an enhanced chemiluminescence detection system (ECL, Amersham) and exposed to Kodak MR film for 40 to 60 seconds. The protein samples of control group on the same blots were used as the positive control in this blotting, and densitometry levels are expressed relative to the control values.

Statistical Analysis
All values are expressed as mean±SEM. The statistical analysis of differences among the groups was done by ANOVA comparison or ANOVA for repeated measures where appropriate and Fisher's exact test for post hoc analyses. Statistical significance was accepted at the level of P<0.05.

	Results

Top Abstract Introduction Growth Hormone Effects in... Effects of Growth Hormone... Methods Results Discussion References

 
Table 1 reports the body weight, left ventricular weight, and in vivo left ventricular pressure. The body weights at baseline and after 14 days of growth hormone administration or no treatment were similar in the 4 groups. Left ventricular weight and the ratio of left ventricular weight to body weight in MI and MI+GH rats were similar and were greater than in control rats. Infarct size (ratio of myocardial scar weight to left ventricular weight) was similar in the MI and MI+GH groups. Growth hormone treatment for 14 days had no effect on left ventricular weight or any hemodynamic parameter in the normal rats (C+GH) compared with untreated control rats. Left ventricular systolic developed pressure per gram was decreased in rats from the MI group but was similar in MI+GH and control rats. Left ventricular end-diastolic pressure was significantly increased in rats in the MI group but was not increased in MI+GH rats compared with the control group.

View this table: [in this window] [in a new window]   Table 1. Characteristics of Control and Postinfarction Rats, by Group

Table 2 reports the characteristics of cell motion and the [Ca²⁺]_i transients in myocytes from the 4 groups under baseline perfusion with 1.2 mmol/L calcium. There were no differences in cell size or any functional parameters in myocytes from normal rats treated with growth hormone (C+GH) compared with normal untreated controls. The end-diastolic cell lengths in myocytes from MI and MI+GH rats were similar and were greater than in myocytes from the control group, which is consistent with left ventricular dilatation in postinfarction heart failure. The fractional cell shortening, peak positive and negative first derivatives of cell motion, time to peak shortening (data not shown), and time to 50% relengthening (data not shown) were similar in myocytes from the 4 groups. Peak systolic [Ca²⁺]_i and end-diastolic [Ca²⁺]_i were similar in myocytes from the 4 groups under the baseline condition of 1.2 mmol/L calcium.

View this table: [in this window] [in a new window]   Table 2. Characteristics (by Group) of Myocyte Function and Intracellular Ca2+

We examined contractile reserve by measuring myocyte shortening in response to the elevation of extracellular calcium from 1.2 to 3.5 mmol/L. Representative tracings from control and C+GH myocytes are shown in Figure 1. Figure 2 shows the changes in fractional cell shortening and peak systolic [Ca²⁺]_i in myocytes from the control and C+GH groups at 1.2 and 3.5 mmol/L perfusate calcium. Fractional cell shortening and peak systolic [Ca²⁺]_i in myocytes of the C+GH group were similar to those in the control group in response to the elevation of perfusate calcium.

View larger version (23K): [in this window] [in a new window]   Figure 1. Top, Representative traces of myocytes from sham-operated control rats with (C+GH) and without (Control) growth hormone treatment in response to elevation of perfusate calcium from 1.2 to 3.5 mmol/L. Upper trace displays cell motion, and lower trace displays [Ca2+]i-sensitive fluorescence transient. In tracings of cell motion, systolic shortening is shown as an upward deflection. Bottom, Representative traces of myocytes from rats with postinfarction failure with (MI+GH) and without (MI) long-term growth hormone treatment.

View larger version (20K): [in this window] [in a new window]   Figure 2. Left, Relationship between perfusate calcium and fractional cell shortening (top) and relationships between perfusate calcium and peak systolic [Ca2+]i (bottom) in myocytes from control and C+GH groups. Right, Same relationships from MI and MI+GH groups.

Representative tracings from MI and MI+GH myocytes are shown in Figure 1. Figure 2 shows the changes in fractional cell shortening and peak systolic [Ca²⁺]_i in myocytes from the MI and MI+GH groups. In response to the elevation of perfusate calcium to 3.5 mmol/L, fractional cell shortening in MI myocytes was depressed compared with that in the control group (P<0.05). In contrast, fractional cell shortening in myocytes from the MI+GH group was significantly greater than that in MI in response to the elevation of perfusate calcium (P<0.01) and was comparable to that in the control group. As shown in Figure 2, the impaired contractile reserve in myocytes from the MI group was related to depressed augmentation of peak systolic [Ca²⁺]_i. In contrast, in the presence of 3.5 mmol/L perfusate calcium, peak systolic [Ca²⁺]_i in myocytes from MI+GH was greater than that in MI rats (P<0.01) and was comparable to the control groups. There were no significant differences in end-diastolic [Ca²⁺]_i between MI and MI+GH rats at either 1.2 or 3.5 mmol/L perfusate calcium. Under pacing conditions of 0.5 Hz, there was no effect of growth hormone on the time course of the calcium transient in control or postinfarction rats.

Figure 3 shows that the relationship between fractional cell shortening and peak systolic [Ca²⁺]_i in control myocytes was similar to that in C+GH rats. In myocytes from the MI+GH rats, both peak systolic [Ca²⁺]_i and cell shortening were greater than in myocytes from MI rats, without an upward and leftward shift of this relationship, which implicates the absence of a change in myofilament responsiveness to calcium within the range of intracellular calcium studied in this experiment.

View larger version (15K): [in this window] [in a new window]   Figure 3. Left, Relationship between perfusate calcium and fractional cell shortening in myocytes from control and C+GH groups. Right, Relationship between peak systolic [Ca2+]i and fractional cell shortening in myocytes from MI and MI+GH groups. Myocytes in each group were exposed to perfusate calcium levels of 1.2 and 3.5 mmol/L.

The effects of postinfarction remodeling and growth hormone administration on gene expression were measured in left ventricular myocytes from MI, MI+GH, and control rats. Expression levels of all genes were analyzed as the ratio to GAPDH. Atrial natriuretic factor (ANF) message levels were similar in the MI+GH versus MI groups (2.8±0.6 versus 1.3±0.3 densitometric units, P=NS) and were not detectable in the control group. The message levels of ß-myosin heavy chain were similar in both MI and MI+GH (3.5±0.9 versus 3.1±0.97) and were increased compared with control (1.0±0.1 densitometric units, P<0.05 versus MI and MI+GH). As shown in Figure 4, there was no depression of message levels of SERCA-2 in MI compared with controls (1.4±0.3 versus 1.0±0.2 densitometric units, P=NS). However, SERCA-2 message levels were increased in myocytes from MI+GH versus MI rats (2.5±0.4 versus 1.4±0.3 densitometric units, P<0.05). Left ventricular protein levels of SERCA-2 (Figure 4) were also increased in MI+GH versus MI rats (177±10% versus 105±11% of control values, P<0.001).

View larger version (22K): [in this window] [in a new window]   Figure 4. Left, Graph and representative Northern blot showing myocyte SERCA-2 message levels normalized to GAPDH and expressed as percent of control group. Right, Graph and representative Western blot showing SERCA-2 protein levels in noninfarcted left ventricular tissue. Values are mean±SEM. *P<0.05, **P<0.01 vs control; P<0.05, P<0.01 vs MI.

	Discussion

Top Abstract Introduction Growth Hormone Effects in... Effects of Growth Hormone... Methods Results Discussion References

 
The present study demonstrates that contractile reserve in response to calcium is depressed in left ventricular myocytes from rats with postinfarction heart failure. Long-term treatment with growth hormone at a dose and a duration that do not promote left ventricular hypertrophy has no effect on myocyte contractile function or size in normal rats. However, long-term growth hormone administration in postinfarction rats is associated with enhanced myocyte contraction and the augmentation of peak systolic [Ca²⁺]_i in response to the elevation of perfusate calcium. These observations show that long-term growth hormone therapy can improve contractile reserve independently of changes in left ventricular mass in rats with postinfarction heart failure.

Contractile Reserve in Postinfarction Myocytes
The absolute level of calibrated calcium may differ, depending on the indicator that is used and the experimental conditions. Nonetheless, these observations are entirely consistent with prior studies of abnormal intracellular calcium regulation in other models of dilated cardiomyopathy. Siri et al³⁷ and Buckelmann et al³⁸ have examined myocytes from failing guinea pig hearts and end-stage human dilated cardiomyopathy, respectively, and observed a similar reduction in peak systolic [Ca²⁺]_i, which is hypothesized to directly contribute to impairment of contractile reserve.

Steady-state myofilament calcium sensitivity was not studied. However, over the range of calcium that was studied, the relationship between cell shortening and [Ca²⁺]_i was not depressed in the failing myocytes from untreated postinfarction rats, which implies that the impaired contractile reserve was not predominantly related to an alteration in the overall responsiveness to calcium. The mechanism of impaired contractile reserve in the postinfarction rat model and human dilated cardiomyopathy appears to differ from early experimental pressure overload rat models in which altered responsiveness to calcium had been observed in both left and right ventricular pressure overload.^{27 39}

Growth Hormone and Contractile Reserve
Our observation supports the hypothesis that growth hormone administration has direct beneficial effects on contractile function in myocytes from postinfarction rats. The underlying molecular mechanism may be related in part to changes in myocyte gene expression. Consistent with previous reports,^{40 41} the expression of left ventricular ß-myosin heavy chain isoform and ANF was upregulated in myocytes from postinfarction rats but was not further modified by growth hormone administration. In humans with dilated cardiomyopathy and depression of peak systolic [Ca²⁺]_i, the intracellular mechanism is speculated to be related to a reduced expression of the sarcoplasmic reticulum ATPase pump (SERCA-2), resulting in impaired sarcoplasmic reticulum calcium loading and release critical for systolic cross-bridge activation.³⁸ In rat models of heart failure, the message and protein levels of SERCA-2 appear to vary with the severity of infarction as well as the stage and duration of heart failure.^{36 42} In the present study, although left ventricular myocyte message levels of SERCA-2 were not depressed in left ventricular myocytes from untreated postinfarction rats, both message and left ventricular protein levels of SERCA-2 were significantly increased in myocytes from postinfarction rats treated with growth hormone.

We postulate that the augmented expression of SERCA-2 may modulate other defects in intracellular calcium regulation, which may contribute to the depression of peak systolic [Ca²⁺]_i in failing hearts during increased work states. Recent studies^{43 44} suggest that abnormalities in the "gain" of sarcoplasmic reticulum calcium release in response to inward calcium current can influence the fractional release of calcium from the sarcoplasmic reticulum. In addition, nuclear resonance spectroscopy experiments by Neubauer et al⁴⁵ have shown that impaired contractile reserve during high-calcium perfusion in postinfarction rat hearts is associated with the reduction of free energy release from ATP hydrolysis (G_ATP) during high work states. Under steady-state conditions, the calcium content of the sarcoplasmic reticulum will depend only on the thermodynamic gradient generated across the sarcoplasmic reticulum membrane and buffering characteristics within its lumen.^{46 47} However, as recently reviewed by Shannon and Bers,⁴⁷ slight non–steady-state reductions in G_ATP will result in a decline in the sarcoplasmic reticulum gradient and calcium load. In this non–steady-state situation, factors that enhance calcium uptake, such as an increase in the number of pumps, may help to sustain a transport rate sufficient to bring sarcoplasmic reticulum calcium content to normal levels.

Limitations
First, intracellular calcium regulation differs in the rat compared with some other species and is characterized by a greater dependence on calcium removal by the sarcoplasmic reticulum relative to the other cellular calcium transport systems.⁴⁸ Second, it is not yet known whether long-term therapy will be associated with beneficial effects or the late cardiomyopathic changes seen in acromegalic heart failure. It is also not known whether treatment with long-term growth hormone administration to stimulate contractility will be associated with the late adverse effect on mortality that has been observed in human clinical trials of agents with mixed positive inotropic and vasodilator properties.⁴⁹ The present study also did not address potential interactive effects of growth hormone therapy with ß-adrenergic blockers, which now play an important role in the long-term treatment of patients after infarction.¹⁹ With these limitations, the present study shows that growth hormone increases contractile reserve in myocytes of postinfarction rats and supports the hypothesis that growth hormone treatment has a direct effect on myocyte contractile function and intracellular calcium regulation.

	Acknowledgments

 
This work was supported in part by National Heart, Lung, and Blood Institute grant HL-38189 (to Drs Lorell, Weinberg, and Tajima), a US Fogarty Fellowship (to Dr Bartunek), and an educational grant from the Department of Cardiovascular Research, Genentech, Inc. We greatly appreciate the constructive criticism and suggestions of Drs Joanne S. Ingwall and Rong Tian from Brigham and Women's Hospital and Harvard Medical School (Boston, Mass). We also acknowledge the technical assistance of Annie Ko from Genentech, Inc. We appreciate the help of John Jaster and Lois Wiltberger in preparing the manuscript.

Received May 14, 1998; revision received August 17, 1998; accepted September 2, 1998.

	References

Top Abstract Introduction Growth Hormone Effects in... Effects of Growth Hormone... Methods Results Discussion References

 
1. Binnerts A, Swart GR, Wilson JHP, Hoogerbrugge N, Pols HAP, Birkenhager JC, Lamberts SWJ. The effects of growth hormone administration in growth hormone deficient adults on bone, protein, carbohydrate and lipid homeostasis, as well as on body composition. Clin Endocrinol. 1992;37:79–87.[Medline] [Order article via Infotrieve]

2. Beshyah SA, Shahi M, Foale R, Johnston DG. Cardiovascular effects of prolonged growth hormone replacement in adults. J Intern Med. 1995;237:35–42.[Medline] [Order article via Infotrieve]

3. Beshyah SA, Shahi M, Skinner E, Sharp P, Foale R, Johnston DG. Cardiovascular effects of growth hormone replacement therapy in hypopituitary adults. Eur J Endocrinol. 1994;130:451–458.[Abstract/Free Full Text]

4. Caidahl K, Edén S, Bengtsson B-Å. Cardiovascular and renal effects of growth hormone. Clin Endocrinol (Oxf). 1994;197:40:393–400.

5. Thuesen L, Jorgensen JOL, Muller JR, Kristein BO, Skakkeboeak NE, Vahl N, Christiansen JS. Short and long-term cardiovascular effects of growth hormone therapy in growth hormone deficient adults. Clin Endocrinol (Oxf). 1994;41:615–620.[Medline] [Order article via Infotrieve]

6. Cuneo RC, Salomon F, Wilmshurst P, Byrne C, Wiles CM, Hesp R, Sönksen PH. Cardiovascular effects of growth hormone treatment in growth-hormone-deficient adults: stimulation of the renin-aldosterone system. Clin Sci (Colch). 1991;81:587–592.[Medline] [Order article via Infotrieve]

7. Haylor J, Singh I, El Nahas AM. Nitric oxide inhibitor prevents vasodilation by insulin-like growth factor I. Kidney Int. 1994;39:333–335.

8. Boger RH, Skamira C, Bode-Boger SM, Brabant G, von sur Muhlen A. Nitric oxide may mediate the hemodynamic effects of recombinant growth hormone in patients with acquired growth hormone deficiency. J Clin Invest. 1996;98:2706–2713.[Medline] [Order article via Infotrieve]

9. Fuller J, Mynett JR, Sugden PH. Stimulation of cardiac protein synthesis by insulin-like growth factors. Biochem J. 1992;282:85–90.

10. Ito H, Hiroe M, Hirata Y, Motoyoshi T, Adachi S, Masayochi S, Koike A, Nogami A, Marumo F. Insulin like growth factor-1 induces hypertrophy with enhanced expression of muscle specific genes in cultured rat cardiomyocytes. Circulation. 1993;87:1715–1721.[Abstract/Free Full Text]

11. Chanson P, Timsit J, Masquet C, Warnet A, Guillausseau PJ, Birman P, Harris AG, Lubetzki J. Cardiovascular effects of the somatostatin analog octreotide in acromegaly. Ann Intern Med. 1990;113:921–925.

12. Penny DG, Dunbar JC, Baylerian MS. Cardiomegaly and haemodynamics in rats with a transplantable growth hormone-secreting tumor. Cardiovasc Res. 1985;19:270–277.[Medline] [Order article via Infotrieve]

13. Strömer H, Cittadini A, Douglas PS, Morgan JP. Exogenously administered growth hormone and insulin-like growth factor-1 alter intracellular Ca²⁺ handling and enhance cardiac performance: in vivo evaluation in the isolated isovolumic buffer-perfused rat heart. Circ Res.. 1996;79:227–236.[Abstract/Free Full Text]

14. Timsit J, Riou B, Bertherat J, Wisnewsky C, Kato NS, Weisberg AS, Lubetzki J, LeCarpentier Y, Winegrad S, Mercadier J-J. Effects of chronic growth hormone hypersecretion on intrinsic contractility, energetics, isomyosin pattern and myosin adenosine triphosphatase activity of rat left ventricle. J Clin Invest. 1990;86:507–515.

15. Mayoux E, Ventura-Clapier R, Timsit J, Béhar-Cohen F, Hoffmann C, Mercadier J-J. Mechanical properties of rat cardiac skinned fibers are altered by chronic growth hormone hypersecretion. Circ Res. 1993;72:57–64.[Abstract/Free Full Text]

16. Fazio S, Sabatini D, Capaldo B, Vigorito C, Giordano A, Guida R, Pardo F, Biondi B, Saccà L. A preliminary study of growth hormone in the treatment of dilated cardiomyopathy. N Engl J Med. 1996;334:809–814.[Abstract/Free Full Text]

17. Cittadini A, Grossman JD, Napoli R, Katz SE, Stromer H, Smith RJ, Clark R, Morgan JP, Douglas PS. Growth hormone attenuates early left ventricular remodeling and improves cardiac function in rats with large myocardial infarction. J Am Coll Cardiol. 1997;29:1109–1116.[Abstract]

18. Castagnino HE, Toranzos FA, Milei J, Weiss V, Beigelman R, Sarchi MI, Bordenave CA, Azcoaga R. Preservation of the myocardial collagen framework by human growth hormone in experimental infarctions and reduction in the incidence of ventricular aneurysms. Int J Cardiol. 1992;35:101–114.[Medline] [Order article via Infotrieve]

19. Castagnino HE, Melei J, Toranzos FA, Weiss V, Beigelman R. Bivalent effects of human growth hormone in experimental myocardial infarcts: protective when administered alone and aggravating when combined with beta blockers. Jpn Heart J. 1990;31:845–855.[Medline] [Order article via Infotrieve]

20. Litwin SE, Raya TE, Anderson PG, Litwin CM, Bressler R, Goldman S. Induction of myocardial hypertrophy after coronary ligation in rats decreases ventricular dilation and improves systolic function. Circulation. 1991;84:1819–1827.[Abstract/Free Full Text]

21. Duerr RL, McKirnan MD, Gim RD, Clark RG, Chien KR, Ross JRJ. Cardiovascular effects of insulin-like growth factor-1 and growth hormone in chronic left ventricular failure in the rat. Circulation. 1996;93:2188–2196.[Abstract/Free Full Text]

22. Yang R, Bunting S, Gillett N, Clark R, Jin H. Growth hormone improves cardiac performance in experimental heart failure. Circulation. 1995;92:262–267.[Abstract/Free Full Text]

23. Jin H, Yang R, Gillett N, Clark RG, Ko A, Paoni NF. Beneficial effects of growth hormone and insulin-like growth factor-1 in experimental heart failure in rats treated with chronic ACE inhibition. J Cardiovasc Pharmacol. 1995;26:420–425.[Medline] [Order article via Infotrieve]

24. Weinberg EO, Schoen FJ, George D, Kagaya Y, Douglas PS, Litwin SE, Schunkert H, Benedict CR, Lorell BH. Angiotensin-converting enzyme inhibition prolongs survival and modifies the transition to heart failure in rats with pressure overload hypertrophy due to ascending aortic stenosis. Circulation. 1994;90:1410–1422.[Abstract/Free Full Text]

25. Capogrossi MC, Kort AA, Spurgeon HA, Lakatta EG. Single adult rabbit and rat cardiac myocytes retain the Ca²⁺-and species-dependent systolic and diastolic contractile properties of the intact muscle. J Gen Physiol. 1986;88:589–613.[Abstract/Free Full Text]

26. Kagaya Y, Weinberg EO, Ito N, Mochizuki T, Barry WH, Lorell BH. Glycolytic inhibition: effects on diastolic relaxation and intracellular calcium handling in hypertrophied rat ventricular myocytes. J Clin Invest. 1995;95:2766–2776.

27. Kagaya Y, Hajjar RJ, Gwathmey JK, Barry WH, Lorell BH. Long-term angiotensin-converting enzyme inhibition with fosinopril improves depressed responsiveness to Ca²⁺ in myocytes from aortic-banded rats. Circulation. 1996;94:2915–2922.[Abstract/Free Full Text]

28. Ito N, Kagaya Y, Weinberg EO, Barry WH, Lorell BH. Endothelin and angiotensin II stimulation of Na⁺-H⁺ exchange is impaired in cardiac hypertrophy. J Clin Invest. 1997;99:125–135.[Medline] [Order article via Infotrieve]

29. Ito N, Bartunek J, Spitzer KW, Lorell BH. Effects of the nitric oxide donor sodium nitroprusside on intracellular pH and contraction in hypertrophied myocytes. Circulation. 1997;95:2303–2311.[Abstract/Free Full Text]

30. Minta A, Kao JP, Tsien RY. Fluorescent indicators for cytosolic calcium based on rhodamine and fluorescein chromophores. J Biol Chem. 1989;264:8171–8178.[Abstract/Free Full Text]

31. Merritt JE, McCarthy SA, Davies MPA, Moores KE. Use of fluo-3 to measure cytosolic Ca²⁺ in platelets and neutrophils. Biochem J. 1990;269:513–519.[Medline] [Order article via Infotrieve]

32. Kao JPY, Harootunian AT, Tsien RY. Photochemically generated cytosolic calcium pulses and their detection by fluo-3. J Biol Chem. 1989;264:8179–8184.[Abstract/Free Full Text]

33. Di Virgilio F, Steinberg TH, Swanson JA, Silverstein SC. Fura-2 secretion and sequestration in macrophages: a blocker of organic anion transport reveals that these processes occur via a membrane transport system for organic anions. J Immunol. 1988;140:915–920.[Abstract]

34. Steadman BW, Moore KB, Spitzer KW, Bridge JHB. A video system for measuring motion in contracting heart cells. IEEE Trans Biomed Eng. 1988;35:264–272.[Medline] [Order article via Infotrieve]

35. Yao A, Natsui H, Spitzer KW, Bridge JH, Barry WH. Sarcoplasmic reticulum and Na⁺/Ca²⁺ exchanger function during early and late relaxation in ventricular myocytes. Am J Physiol. 1997;273:H2765–H2773.[Abstract/Free Full Text]

36. Qi M, Shannon TR, Euler DE, Bers DM, Samarel AM. Down regulation of sarcoplasmic reticulum Ca²⁺-ATPase during progression of left ventricular hypertrophy. Am J Physiol. 1997;272:H2416–H2424.[Abstract/Free Full Text]

37. Siri FM, Krueger J, Nordin C, Ming Z, Aronson RS. Depressed intracellular calcium transient and contraction in myocytes from hypertrophied and failing guinea pig hearts. Am J Physiol. 1991;261:H514–H530.[Abstract/Free Full Text]

38. Buckelmann DJ, Nabauer M, Erdmann E. Intracellular calcium handing in isolated ventricular myocytes from patients with terminal heart failure. Circulation. 1992;85:1046–1055.[Abstract/Free Full Text]

39. Fan D, Wannenburg T, de Tombe PP. Decreased myocyte tension development and calcium responsiveness in rat right ventricular pressure overload. Circulation. 1997;6:2312–2317.

40. Orenstein TL, Parker TG, Butany JW, Goodman JM, Dawood F, Wen W-H, Wee L, Martino T, McLaughlin PR, Liv PP. Favorable left ventricular modeling following large myocardial infarction by exercise training. J Clin Invest. 1995;96:858–866.

41. Wollert KC, Studer R, von Vulow B, Duxler H. Survival after myocardial infarction in the rat: role of tissue angiotensin-converting enzyme inhibitor. Circulation. 1994;90:2451–2467.

42. Zarain-Herzberg A, Afzol N, Elimban V, Dhalla NS. Decreased expression of cardiac sarcoplasmic reticulum Ca²⁺-pump ATPase in congestive heart failure due to myocardial infarction. Mol Cell Biochem. 1996;163/164:285–290.

43. McCall E, Ginsburg KS, Bassani RA, Shannon TR, Qi M, Samarel AM, Bers DM. Ca flux, contractility, and excitation–contraction coupling in hypertrophic rat myocytes. Am J Physiol. 1998;274:H1348–H1360.

44. Gomez AM, Valdivia HH, Cheng H, Lederer MR, Santana LF, Cannell MB, McCune SA, Altschuld RA, Lederer WJ. Defective excitation-contraction coupling in experimental cardiac hypertrophy and heart failure. Science. 1997;276:800–806.[Abstract/Free Full Text]

45. Neubauer S, Horn M, Naumann A, Tian R, Hu K, Laser M, Freidrich J, Gaudron P, Schnackerz K, Ingwall JS, Ertl G. Impairment of energy metabolism in intact residual myocardium of rat hearts with chronic myocardial infarction. J Clin Invest. 1995;95:1092–1100.

46. Tian R, Ingwall JS. Energetic basis for reduced contractile reserve in isolated rat hearts. Am J Physiol. 1996;270:H1207–H1216.[Abstract/Free Full Text]

47. Shannon TR, Bers DM. Assessment of intra-SR free [Ca] and buffering in the rat heart. Biophys J. 1997;73:1524–1531.[Medline] [Order article via Infotrieve]

48. Bers DM, Bassani JW, Bassani RA. Na-Ca exchange and Ca fluxes during contraction and relaxation in mammalian ventricular muscle. Ann N Y Acad Sci. 1996;779:430–442.[Medline] [Order article via Infotrieve]

49. Packer M. The search for the ideal inotropic agent. N Engl J Med. 1993;329:201–202.[Free Full Text]

This article has been cited by other articles:

				R. Rabkin, I. Awwad, Y. Chen, E. A. Ashley, D. Sun, S. Sood, W. Clusin, P. Heidenreich, G. Piecha, and M.-L. Gross Low-Dose Growth Hormone is Cardioprotective in Uremia J. Am. Soc. Nephrol., September 1, 2008; 19(9): 1774 - 1783. [Abstract] [Full Text] [PDF]

				S. Fazio, E. A. Palmieri, F. Affuso, A. Cittadini, G. Castellano, T. Russo, A. Ruvolo, R. Napoli, and L. Sacca Effects of Growth Hormone on Exercise Capacity and Cardiopulmonary Performance in Patients with Chronic Heart Failure J. Clin. Endocrinol. Metab., November 1, 2007; 92(11): 4218 - 4223. [Abstract] [Full Text] [PDF]

				L. Groban, N. A. Pailes, C. D. L. Bennett, C. S. Carter, M. C. Chappell, D. W. Kitzman, and W. E. Sonntag Growth Hormone Replacement Attenuates Diastolic Dysfunction and Cardiac Angiotensin II Expression in Senescent Rats J. Gerontol. A Biol. Sci. Med. Sci., January 1, 2006; 61(1): 28 - 35. [Abstract] [Full Text] [PDF]

				S. Marleau, M. Mulumba, D. Lamontagne, and H. Ong Cardiac and peripheral actions of growth hormone and its releasing peptides: Relevance for the treatment of cardiomyopathies Cardiovasc Res, January 1, 2006; 69(1): 26 - 35. [Abstract] [Full Text] [PDF]

				C. J. Pemberton, H. Tokola, Z. Bagi, A. Koller, J. Pontinen, A. Ola, O. Vuolteenaho, I. Szokodi, and H. Ruskoaho Ghrelin induces vasoconstriction in the rat coronary vasculature without altering cardiac peptide secretion Am J Physiol Heart Circ Physiol, October 1, 2004; 287(4): H1522 - H1529. [Abstract] [Full Text] [PDF]

				V. Jayasankar, L. T. Bish, T. J. Pirolli, M. F. Berry, J. Burdick, and Y. J. Woo Local myocardial overexpression of growth hormone attenuates postinfarction remodeling and preserves cardiac function Ann. Thorac. Surg., June 1, 2004; 77(6): 2122 - 2129. [Abstract] [Full Text] [PDF]

				L. Dalla Libera, B. Ravara, M. Volterrani, V. Gobbo, M. Della Barbera, A. Angelini, D. D. Betto, E. Germinario, and G. Vescovo Beneficial effects of GH/IGF-1 on skeletal muscle atrophy and function in experimental heart failure Am J Physiol Cell Physiol, January 1, 2004; 286(1): C138 - C144. [Abstract] [Full Text] [PDF]

				M. Iwase, H. Kanazawa, Y. Kato, T. Nishizawa, F. Somura, R. Ishiki, K. Nagata, K. Hashimoto, K. Takagi, H. Izawa, et al. Growth hormone-releasing peptide can improve left ventricular dysfunction and attenuate dilation in dilated cardiomyopathic hamsters Cardiovasc Res, January 1, 2004; 61(1): 30 - 38. [Abstract] [Full Text] [PDF]

				K. C Wollert and H. Drexler Growth hormone and proinflammatory cytokine activation in heart failure: Just a new verse to an old sirens' song? Eur. Heart J., December 2, 2003; 24(24): 2164 - 2165. [Full Text] [PDF]

				K. Ito, M. Nakayama, F. Hasan, X. Yan, M. D. Schneider, and B. H. Lorell Contractile Reserve and Calcium Regulation Are Depressed in Myocytes From Chronically Unloaded Hearts Circulation, March 4, 2003; 107(8): 1176 - 1182. [Abstract] [Full Text] [PDF]

				A. S. Khan, D. C. Sane, T. Wannenburg, and W. E. Sonntag Growth hormone, insulin-like growth factor-1 and the aging cardiovascular system Cardiovasc Res, April 1, 2002; 54(1): 25 - 35. [Abstract] [Full Text] [PDF]

				N. Nagaya, K. Miyatake, M. Uematsu, H. Oya, W. Shimizu, H. Hosoda, M. Kojima, N. Nakanishi, H. Mori, and K. Kangawa Hemodynamic, Renal, and Hormonal Effects of Ghrelin Infusion in Patients with Chronic Heart Failure J. Clin. Endocrinol. Metab., December 1, 2001; 86(12): 5854 - 5859. [Abstract] [Full Text] [PDF]

				R. C. Cuneo GH and Cardiac Failure J. Clin. Endocrinol. Metab., October 1, 2001; 86(10): 4635 - 4637. [Full Text] [PDF]

				N. Nagaya, M. Uematsu, M. Kojima, Y. Ikeda, F. Yoshihara, W. Shimizu, H. Hosoda, Y. Hirota, H. Ishida, H. Mori, et al. Chronic Administration of Ghrelin Improves Left Ventricular Dysfunction and Attenuates Development of Cardiac Cachexia in Rats With Heart Failure Circulation, September 18, 2001; 104(12): 1430 - 1435. [Abstract] [Full Text] [PDF]

				A. S. Khan, C. D. Lynch, D. C. Sane, M. C. Willingham, and W. E. Sonntag Growth Hormone Increases Regional Coronary Blood Flow and Capillary Density in Aged Rats J. Gerontol. A Biol. Sci. Med. Sci., August 1, 2001; 56(8): B364 - 371. [Abstract] [Full Text] [PDF]

				T. Wannenburg, A. S. Khan, D. C. Sane, M. C. Willingham, T. Faucette, and W. E. Sonntag Growth hormone reverses age-related cardiac myofilament dysfunction in rats Am J Physiol Heart Circ Physiol, August 1, 2001; 281(2): H915 - H922. [Abstract] [Full Text] [PDF]

				N. Nagaya, M. Kojima, M. Uematsu, M. Yamagishi, H. Hosoda, H. Oya, Y. Hayashi, and K. Kangawa Hemodynamic and hormonal effects of human ghrelin in healthy volunteers Am J Physiol Regulatory Integrative Comp Physiol, May 1, 2001; 280(5): R1483 - R1487. [Abstract] [Full Text] [PDF]

				M. K. King, D. M. Gay, L. C. Pan, J. H. McElmurray III, J. W. Hendrick, C. Pirie, A. Morrison, C. Ding, R. Mukherjee, and F. G. Spinale Treatment With a Growth Hormone Secretagogue in a Model of Developing Heart Failure : Effects on Ventricular and Myocyte Function Circulation, January 16, 2001; 103(2): 308 - 313. [Abstract] [Full Text] [PDF]

				K. Ito, X. Yan, M. Tajima, Z. Su, W. H. Barry, and B. H. Lorell Contractile Reserve and Intracellular Calcium Regulation in Mouse Myocytes From Normal and Hypertrophied Failing Hearts Circ. Res., September 29, 2000; 87(7): 588 - 595. [Abstract] [Full Text] [PDF]

				Y. Iwanaga, Y. Kihara, T. Yoneda, T. Aoyama, and S. Sasayama Modulation of in vivo cardiac hypertrophy with insulin-like growth factor-1 and angiotensin-converting enzyme inhibitor: relationship between change in myosin isoform and progression of left ventricular dysfunction J. Am. Coll. Cardiol., August 1, 2000; 36(2): 635 - 642. [Abstract] [Full Text] [PDF]

				B. Ding, R. L. Price, E. C. Goldsmith, T. K. Borg, X. Yan, P. S. Douglas, E. O. Weinberg, J. Bartunek, T. Thielen, V. V. Didenko, et al. Left Ventricular Hypertrophy in Ascending Aortic Stenosis Mice : Anoikis and the Progression to Early Failure Circulation, June 20, 2000; 101(24): 2854 - 2862. [Abstract] [Full Text] [PDF]

				K. J. Osterziel, W. F. Blum, O. Strohm, and R. Dietz The Severity of Chronic Heart Failure due to Coronary Artery Disease Predicts the Endocrine Effects of Short- Term Growth Hormone Administration J. Clin. Endocrinol. Metab., April 1, 2000; 85(4): 1533 - 1539. [Abstract] [Full Text]

				J. Bartunek, E. O. Weinberg, M. Tajima, S. Rohrbach, S. E. Katz, P. S. Douglas, and B. H. Lorell Chronic NG-Nitro-L-Arginine Methyl Ester-Induced Hypertension : Novel Molecular Adaptation to Systolic Load in Absence of Hypertrophy Circulation, February 1, 2000; 101(4): 423 - 429. [Abstract] [Full Text] [PDF]

				A. Tivesten, E. Bollano, K. Caidahl, V. Kujacic, X. Y. Sun, T. Hedner, A. Hjalmarson, B.-A. Bengtsson, and J. Isgaard The Growth Hormone Secretagogue Hexarelin Improves Cardiac Function in Rats after Experimental Myocardial Infarction Endocrinology, January 1, 2000; 141(1): 60 - 66. [Abstract] [Full Text] [PDF]

				U Ravens and D Dobrev Regulation of sarcoplasmic reticulum Ca2+-ATPase and phospholamban in the failing and nonfailing heart Cardiovasc Res, January 1, 2000; 45(1): 245 - 252. [Full Text] [PDF]

				S. Rohrbach, X. Yan, E. O. Weinberg, F. Hasan, J. Bartunek, M. A. Marchionni, and B. H. Lorell Neuregulin in Cardiac Hypertrophy in Rats With Aortic Stenosis : Differential Expression of erbB2 and erbB4 Receptors Circulation, July 27, 1999; 100(4): 407 - 412. [Abstract] [Full Text] [PDF]

				E. O. Weinberg, C. D. Thienelt, S. E. Katz, J. Bartunek, M. Tajima, S. Rohrbach, P. S. Douglas, and B. H. Lorell Gender differences in molecular remodeling in pressure overload hypertrophy J. Am. Coll. Cardiol., July 1, 1999; 34(1): 264 - 273. [Abstract] [Full Text] [PDF]

				B. Ding, R. L. Price, T. K. Borg, E. O. Weinberg, P. F. Halloran, and B. H. Lorell Pressure Overload Induces Severe Hypertrophy in Mice Treated With Cyclosporine, an Inhibitor of Calcineurin Circ. Res., April 2, 1999; 84(6): 729 - 734. [Abstract] [Full Text] [PDF]

				J. Ross Jr Growth Hormone, Cardiomyocyte Contractile Reserve, and Heart Failure Circulation, January 12, 1999; 99(1): 15 - 17. [Full Text] [PDF]

				K. Ito, X. Yan, X. Feng, W. J. Manning, W. H. Dillmann, and B. H. Lorell Transgenic Expression of Sarcoplasmic Reticulum Ca2+ ATPase Modifies the Transition From Hypertrophy to Early Heart Failure Circ. Res., August 31, 2001; 89(5): 422 - 429. [Abstract] [Full Text] [PDF]

This Article Abstract Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Request Permissions Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Tajima, M. Articles by Lorell, B. H. Search for Related Content PubMed PubMed Citation Articles by Tajima, M. Articles by Lorell, B. H. Pubmed/NCBI databases Compound via MeSH Substance via MeSH Hazardous Substances DB CALCIUM COMPOUNDS CALCIUM, ELEMENTAL Medline Plus Health Information Heart Attack Heart Failure Related Collections Contractile function Gene expression Mechanism of atherosclerosis/growth factors