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Am J Physiol Heart Circ Physiol 275: H393-H399, 1998;
0363-6135/98 $5.00
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Vol. 275, Issue 2, H393-H399, August 1998

Effects of growth hormone and IGF-I on cardiac hypertrophy and gene expression in mice

Nobuaki Tanaka1, Tsutomu Ryoke1, Minoru Hongo1, Lan Mao1, Howard A. Rockman1, Ross G. Clark2, and John Ross Jr.1

1 Division of Cardiology, Department of Medicine, University of California, San Diego, La Jolla 92093; and 2 Genentech, South San Francisco, California 94080

    ABSTRACT
Top
Abstract
Introduction
Methods
Results
Discussion
References

Cardiac hypertrophic and contractile responses were studied in mice administered growth hormone (GH) and insulin-like growth factor (IGF-I) (8 mg · kg-1 · day-1), alone or in combination (IGF-I/GH), for 2 wk. Also, changes in expression of selected left ventricular (LV) genes in response to IGF-I/GH were compared with those in other forms of cardiac hypertrophy. GH or IGF-I alone at three to four times the usual dose in rats failed to produce increases in heart and LV weights and hemodynamic effects; however, IGF-I/GH was synergistic, increasing body weight and LV weights by 39 and 35%, respectively. A measure of myocardial contractility (maximal first derivative of LV pressure, catheter-tip micromanometry) was increased by 34% in the IGF/GH group, related in part to a force-frequency effect, since the heart rate increased by 21%. Other mice were treated surgically to produce pressure overload (transverse aortic constriction) or volume overload (arteriovenous fistula) for 2 wk; LV weights were then matched to those in the IGF-I/GH group, and mRNA levels of selected markers were assessed. In contrast to the increased mRNA levels of atrial natriuretic factor, alpha -skeletal actin, and collagen III generally observed in overloaded hearts, changes in IGF-I/GH-treated mice were not significant. Thus high-dose IGF-I/GH produce cardiac hypertrophy and a positive inotropic effect without causing significant changes in expression of fetal and other selected myocardial genes, suggesting that this hypertrophy may be of a more physiological type than that due to mechanical overload.

insulin-like growth factor I; myocardial contractility; pressure overload; volume overload; messenger ribonucleic acid; mouse left ventricle; atrial natriuretic peptide

    INTRODUCTION
Top
Abstract
Introduction
Methods
Results
Discussion
References

CARDIAC HYPERTROPHY is well known to occur in response to various stimuli, such as pressure and volume overload and exercise (23). In the rat, pressure-overload hypertrophy is associated with marked changes in cardiac gene expression (4, 12, 17, 21), some of which are not observed with volume-overload hypertrophy (2). Also, the normal rat has been reported to respond to either growth hormone (GH) or insulin-like growth factor (IGF-I) administration with hypertrophy (9, 32), an increase (6) or no change (32) in myocardial contractility, and unchanged ventricular expression of mRNA for atrial natriuretic factor (ANF) and alpha -skeletal actin (6). We have previously suggested that the left ventricular (LV) hypertrophy produced by IGF-I in the noninfarcted portion of the rat LV after myocardial infarction may be relatively physiological in nature, since it was not associated with a further decrease in capillary density or increase in collagen content (9), changes known to accompany hypertrophy due to cardiac overload (29, 30).

Despite extensive use of murine models, there is scant information available in the mouse concerning changes in cardiac gene expression in the hypertrophy produced by IGF-I or GH administration compared with data associated with hypertrophy of a comparable degree caused by mechanical cardiac overload. Moreover, little is known about the effects of IGF-I and GH on myocardial contractility in the normal mouse. Accordingly, in the present study the effects of IGF-I and GH, alone and in combination (IGF-I/GH), on hemodynamic variables, cardiac hypertrophy, and organ growth were investigated in normal mice, and the expression of selected cardiac genes in IGF-I/GH-treated mice was compared with that in mice having comparable degrees of hypertrophy induced by pressure or volume overload.

    METHODS
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Abstract
Introduction
Methods
Results
Discussion
References

Mice were handled according to the animal welfare regulations of the University of California, San Diego, and the experimental protocol was approved by the Animal Subjects Committee of that institution.

Protocol for IGF-I- and GH-Treated Mice

Among 43 female C57BL/6 mice, the mean age of the four groups ranged from 91.5 to 94.5 days, with no significant difference between groups. The mice in each study group were treated for 14 days: 11 mice received recombinant human (rh) IGF-I (8 mg · kg-1 · day-1 by osmotic minipump) together with placebo (saline) injections (0.1 ml sc twice a day); 10 mice received rhGH (4 mg/kg sc twice a day) together with continuous vehicle infusion by minipump (sodium acetate buffer); 12 mice received combined IGF-I/GH (total 8 mg · kg-1 · day-1 of each); and 10 control mice received placebo injections and vehicle infusions. The high dose of IGF-I was based on pilot studies with IGF-I in the mouse, in which it was determined that doses previously employed in rats (3-6 mg · kg-1 · day-1) were inadequate to promote increases in body weight (BW). GH was administered every morning and evening, including the morning of the terminal study day, and the dose was increased from that given in a previous study using rat GH in mice (16).

After induction of anesthesia (100 mg/kg ketamine and 5 mg/kg xylazine), the interscapular area was shaved and disinfected with chlorhexidine. A 1-cm skin incision was then made on the back between scapulae, an osmotic minipump (Alzet 2002, Alza, Palo Alto, CA) was implanted subcutaneously, and the wound was closed with a 5-0 silk suture. The surgery was accomplished in <10 min, and the mice were allowed to recover. Instruments were thoroughly cleaned with chlorhexidine solution and alcohol before and after each operation and at the beginning and end of each day.

Hemodynamic studies. Fourteen days after pump implantation, the mice were anesthetized as described above, and the neck and chest were shaved. A small incision was made in the midline of the neck, and the animals were intubated and placed on positive-pressure respiration (Harvard Apparatus, S. Natick, MA) with 0.5 ml tidal volume at 100-110 respirations/min (21). A catheter was inserted into left jugular vein for saline infusion, and another catheter was inserted into the right carotid artery for measurement of aortic pressure with a fluid-filled transducer (Statham P50). Both vagal nerves were cut. The left chest was then opened, and a 2-F Millar catheter-tip micromanometer (model SPR-407, Millar Instruments, Houston, TX) was inserted into the LV through the mitral valve by puncturing the left atrial appendage, as described elsewhere (19). After hemodynamic conditions had stabilized, the left ventricular pressure (LVP) and aortic pressure were digitized at a sampling rate of 2,000 samples/s, and LVP and the maximal and minimal first derivatives (LV dP/dtmax and LV dP/dtmin) were determined with a beat-averaging program (19). The animals were then killed with an overdose of pentobarbital sodium, and the organ and cardiac chamber weights were determined.

Protocol for Mice With Pressure and Volume Overload

To compare cardiac gene expression in treated mice with that in other forms of hypertrophy, groups of 10-12 mice 12-13 wk of age were subjected to transverse aortic constriction (TAC) or to creation of an infrarenal arteriovenous (AV) fistula. After ketamine-xylazine anesthesia and tracheal intubation with mechanical ventilation, aortic constriction was produced (21). In brief, through a small anterior thoracic incision, a ligature was placed around the aortic arch between the innominate and subclavian arteries and tied against a 27-gauge needle, which was then rapidly withdrawn. The incision was then closed, and the animal was allowed to recover. Five mice were given an AV fistula; after anesthesia and intubation, a midline abdominal incision was performed and a 1-mm-diameter connection was created between the aorta and inferior vena cava as described previously (26). Two weeks later, the mice were killed for postmortem studies (see below).

Postmortem Studies

The hearts in all groups (TAC, AV fistula, IGF-I/GH, and sham) were excised, and each chamber was dissected. The LV, right ventricle (RV), right atrium, and left atrium were weighed with an analytic balance (Sauter RE1614, Switzerland), and the LV was quickly frozen with liquid nitrogen and stored in a freezer at -70°C for subsequent Northern blot analyses. The liver, spleen, kidneys, lungs, and right gastrocnemius muscle also were weighed, and the tibial length (TL) was measured.

Studies of gene expression were performed in mice that underwent TAC, AV fistula, and IGF-I/GH treatment and in sham-operated mice. From the IGF-I/GH-treated mice, a representative group of LVs (n = 5) was selected for comparison with those from mice subjected to mechanical overload. From the TAC and AV fistula groups, five LVs with weights comparable to those in the IGF-I/GH group were identified. Because an increase in BW as well as LV weight (LVW) occurred in the IGF-I/GH group, resulting in an unchanged LVW/BW, LVW/TL values (33) were matched in the four groups and are presented together with the absolute LVW and LVW/BW data.

Blood collection and analyses of plasma GH and IGF-I levels. The last dose of GH was given 4-6 h before the hemodynamic study, and, just before the animals were killed, 1 ml of blood was obtained in a heparinized syringe from the LV cavity and centrifuged at 3,000 rpm for 5 min. The plasma obtained was stored at -70°C for subsequent analysis. Human GH was measured by a sensitive and specific ELISA (3), which does not detect rat GH. Total IGF-I levels were measured after acid-ethanol extraction by RIA, with human IGF-I (Genentech M3-RD1) as the standard and rabbit anti-IGF-I polyclonal antiserum (10, 34).

mRNA measurements. Total RNA was isolated from the LVs of experimental and control mice by a modified guanidinium thiocyanate technique (RNAzol, Cinna/Biotecx Laboratories, Houston, TX). RNA (10 µg) was size fractionated by denaturing gel electrophoresis and transferred to nylon membranes by capillary action, and 32P-labeled cDNA probes were added as described elsewhere (21). Quantitative evaluation of autoradiograms was performed by laser densitometry of mRNA bands, and band intensities were normalized to the hybridization signal obtained with glyceraldehyde-3-phosphate dehydrogenase (GAPDH) RNA. Exposure times were chosen to obtain densitometric scans within the linear response range of the radiographic film. cDNA probes were specific for mRNAs encoding ANF, alpha -skeletal muscle actin, collagen III, sarco(endo)plasmic reticular Ca2+-ATPase (SERCA), and phospholamban.

Statistics

Data are shown as means ± SD with the exception of mRNA data, which are shown as means ± SE. A paired t-test was used for the evaluation of BW changes before and after 2 wk of treatment. A single-factor ANOVA was used to analyze the effects of IGF-I and GH treatment on organ weights and on hemodynamic data by using a post hoc Scheffé's test. For the analysis of differences in mRNA levels (in arbitrary units), a one-factor ANOVA was performed by using post hoc testing of mean densitometric values for each transcript by the Newman-Keuls method. Statistical significance was identified as P < 0.05.

    RESULTS
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Abstract
Introduction
Methods
Results
Discussion
References

Studies in Mice Treated With GH and IGF-I

Body weights. BWs were closely matched at the beginning of the study. Two weeks later, when the animals were killed, the average BW had increased by 18% with IGF-I, 7% with GH, and significantly by 39% with IGF-I/GH (Fig. 1). The increases with IGF-I and GH were not significant vs. controls (Table 1).


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  		Fig. 1.   Body weights (BW) and cardiovascular weights in control and treated mice. Insulin-like growth factor (IGF-I), growth hormone (GH), and a combination of IGF-I and GH (IGF-I/GH) were administered. LV, left ventricular; TL, tibial length. * P < 0.01, IGF-I/GH vs. control; dagger  P < 0.01 vs. GH; ddager  P < 0.03 vs. IGF-I. Bars represent means ± SD.

                              
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  		Table 1.   Weight data in controls and IGF-I- and GH-treated groups

Organ weights. TL, which provides an indicator of the lean body mass (30), was slightly but significantly increased in the IGF-I/GH group compared with controls. Significant increases occurred in kidney and lung weights in the IGF-I group but not the GH group, whereas with IGF-I/GH all weights were significantly higher than the other three groups (P < 0.001; Table 1).

Heart weights. LVW was slightly but not significantly greater in the IGF-I and GH groups compared with controls, but the 35.5% increase with IGF-I/GH was significant compared with the other three groups. LVW/BW showed no statistically significant differences between groups. However, absolute LVW and the LVW/TL were significantly increased only in the IGF-I/GH group (Fig. 1).

In mice treated with GH or IGF-I alone, RV weight was not significantly increased compared with controls. However, the increase with IGF-I/GH was significant compared with the other three groups (Table 1).

Hemodynamic variables. LV systolic pressure was slightly but significantly higher with IGF-I/GH compared with IGF-I, and the heart rate was also significantly higher by 21% compared with controls (Fig. 2). An index of myocardial contractility, LV dP/dtmax, was significantly increased by 39% with IGF-I/GH (5,729 mmHg/s) compared with controls (4,394 mmHg/s) and with both other groups (Fig. 2). The LV end-diastolic pressures were not significantly different, averaging 2.2 ± 1.3 in controls and 2.1 ± 1.2 and 1.8 ± 0.8 mmHg in the IGF-I and IGF-I/GH groups, respectively. The LV dP/dtmin, an index of LV relaxation, was also not significantly different among the groups (data not shown).


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  		Fig. 2.   Hemodynamic data in control and treated mice. HR, heart rate; SP, systolic pressure; EDP, end-diastolic pressure, and maximal first derivative of LV pressure (LV dP/dtmax). * P < 0.001, IGF-I/GH vs. control; dagger  P < 0.001 vs. GH; ddager  P < 0.03 vs. IGF-I. Bars represent means ± SD.

GH and IGF levels. IGF-I levels were increased in the IGF-I-treated group and further elevated by 58% in the IGF-I/GH group (Table 2). In the GH group, IGF-I was slightly elevated [not significant (NS)]. rhGH was undetectable in controls and the IGF-I group, not significantly increased in the GH group and increased in the IGF-I/GH group (Table 2).

                              
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  		Table 2.   Plasma levels of IGF-I and GH

Studies of Gene Expression in IGF-I/GH-Treated and Overloaded Mouse Hearts

Table 3 summarizes the data on BW and heart and chamber weights in the controls (sham operated) and TAC, AV fistula, and IGF-I/GH groups. The absolute LVWs were increased significantly to a comparable degree compared with controls in all three groups (Fig. 3), and although LVW/BW was not increased in the IGF-I/GH group due to the increased BW (Table 3), LVW/TL was significantly increased and comparable in all three groups compared with controls (Fig. 3).

                              
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  		Table 3.   Weight data in sham-operated, mechanical, overload, and IGF-I/GH groups


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  		Fig. 3.   LV weights in sham and hypertrophied hearts. Sham, sham-operated mice; TAC, transverse aortic constriction; AVF, mice with arteriovenous fistula; IGF-I/GH, mice treated with IGF-I/GH in combination. * P < 0.01 vs. sham. Bars represent means ± SD.

The Northern blots for the various cDNA probes in the four groups of mice are shown in Fig. 4, and the changes in mRNA levels, corrected for GAPDH and expressed in arbitrary units, are shown in Fig. 5. The TAC group showed the expected marked induction of ANF, alpha -skeletal actin, and collagen III mRNA levels, with no change in mRNA levels of SERCA and phospholamban. In the AV fistula group, ANF, SERCA, and alpha -skeletal actin mRNA were not significantly different compared with controls, whereas phospholamban and collagen III mRNA were increased (Fig. 5). In the IGF-I/GH group, no change was observed in ANF, alpha -skeletal actin, SERCA, and phospholamban mRNA levels, and the tendency for collagen III mRNA to be increased was not significant.


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  		Fig. 4.   Northern blot analysis in sham and hypertrophic hearts. mRNA levels are shown in mouse LV after sham operation (control, n = 5), TAC (n = 5), AV fistula (AVF; n = 5), and IGF-I/GH treatment [n = 4; in 1 animal in this group, RNA was degraded (lane 3), and this animal was not included in analysis]. Filters were hybridized with 32P-labeled cDNA probes, and transcripts were detected by autoradiography. Each lane represents RNA isolated from a different mouse ventricle. The following cDNA probes were used: ANF, atrial natriuretic factor; alpha SkActin, alpha -skeletal actin; Coll III, collagen III; SERCA, sarco(endo)plasmic reticular Ca2+-ATPase; PLB, phospholamban; GAPDH, glyceraldehyde-3-phosphate dehydrogenase. The 2 PLB transcripts noted are due to different polyadenylation signals. Data represent means ± SE.


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  		Fig. 5.   Summary of Northern blot data. Densitometric quantification of various autoradiograms (arbitrary units). See Fig. 4 for details. Upper and lower PLB band signal intensities used in quantification. * P < 0.05; ** P < 0.0005; dagger  P = 0.05 vs. control for each mRNA probed. Bars represent means ± SE.

    DISCUSSION
Top
Abstract
Introduction
Methods
Results
Discussion
References

Several conclusions can be drawn from this study concerning the effects of IGF-I and GH in the normal mouse. 1) Doses of rhIGF-I and rhGH alone three to four times those currently used in the rat did not increase BW with GH, caused a mild increase with IGF-I, and failed to increase the cardiac weights in either group. 2) IGF-I and GH in combination at those doses substantially increased both BW and LVW (by 39 and 35.5%, respectively), associated with a marked further enhancement of the plasma IGF-I level. 3) Enhanced LV myocardial contractility, evidenced by augmented LV dP/dtmax, was evident only in the IGF-I/GH group and was associated with an increase in heart rate. 4) LV hypertrophy produced by IGF-I/GH was comparable to that in mice with pressure and volume overload, but the pattern of gene expression differed. In particular, there was no activation of the fetal gene program (ANF and alpha -skeletal actin; Refs. 17 and 24), and the increase of collagen III was variable among animals and not statistically significant compared with controls. Thus gene expression in the hypertrophy induced by IGF-I/GH resembled that in volume-overload more than the pressure-overload hypertrophy, and it might be more physiological in nature.

Effects of rhIGF-I and rhGH on Body and Cardiac Weights

In the normal rat, doses of IGF-I of 3 mg · kg-1 · day-1 (9) and GH of 3.5 mg · kg-1 · day-1 (6) produce substantial increases in BW and heart weight, but in the mouse, we found that 8 mg · kg-1 · day-1 of rhIGF-I or rhGH alone were ineffective. This may relate in part to species differences; e.g., mouse IGF-I differs from rat IGF-I by several amino acids, and their receptors might respond differently to rhIGF-I. It would have been useful to have cell volume measurements in the control and IGF-I/GH groups, since most of the changes in myocyte size due to GH occurs in cell length rather than cross-sectional area (9, 15), but this was not feasible because the LV was quickly frozen for mRNA determinations. However, there was a highly significant 35.5% increase in absolute LVW in the IGF-I/GH group (which was matched by increased BW) compared with controls. TL in the IGF-I/GH group increased by only 5%, so that LVW/TL also increased significantly and provides a better measure of lean body mass than LVW/BW (9, 33). Therefore, in the absence of any reason for myocardial edema, we consider that these two measurements provide good evidence for LV hypertrophy in the IGF-I/GH group.

The synergistic trophic effect of IGF-I/GH was striking and was associated with a significant further increase (by 58%) in the plasma IGF-I level, which could explain a sizable part but probably not all of the enhanced effects in the IGF-I/GH group. Thus the combination of IGF-I and GH has previously been shown to be substantially more anabolic than either IGF-I or GH alone in human subjects, and several mechanisms for this effect were proposed by Kupfer et al. (14) in addition to an expected further increase in the plasma IGF-I: 1) GH reverses the insulin-suppressive effect of IGF-I, and the higher insulin concentration could have inhibited proteolysis and enhanced the anabolic effect of IGF-I; 2) the combination could lead to further protein sparing, since GH increases protein synthesis, whereas IGF-I inhibits proteolysis; and 3) the induction of the binding protein 3 for IGF-I and the acid-labile subunit by IGF-I/GH might account for a more stable IGF-I pool (14). Variability in the responses of circulating rhGH is expected, since blood sampling at the end of each experiment could not be precisely timed with the rhGH injections, and the rhGH level declines rapidly after injection. Thus, in contrast to the stable IGF-I levels, a single blood sample is not likely to be representative of the mean rhGH value throughout the day.

Effects of IGF-I and GH on Myocardial Contractility

Myocardial contractility, assessed by LV dP/dtmax, was found to be significantly increased in these normal mice only by combined IGF-I and GH administration. We have previously found LV dP/dtmax to be normal in the markedly hypertrophied LV of transgenic mice overexpressing Ras (11), and LV dP/dtmax, when measured with a high-fidelity catheter, is generally accepted as a reliable measure of contractility provided there is no change in the LV preload (16). The LV end-diastolic pressures were not increased in the IGF-I/GH group (they were slightly lower than in controls), and peak LVPs were minimally different, so LV dP/dtmax should provide an adequate contractility measurement in this setting.

On the basis of recent studies showing a positive force-frequency relationship in the normal mouse heart (20), the increased heart rate in the IGF-I/GH group undoubtedly contributed to the enhanced contractility, although the increase of LV dP/dtmax (34%) was greater than the effect in contractility predicted from the 21% increase in heart rate. Thus, in our earlier study, increases in heart rate were associated with proportionally greater increases in LV dP/dtmax (20).

IGF-I increases heart rate, cardiac output, and contractility when given to normal human subjects (8, 27) and GH-deficient adult patients (1, 5). In rats, Cittadini et al. (6) reported that IGF-I alone (3 mg · kg-1 · day-1) or GH (3.5 mg · kg-1 · day-1) given for 4 wk increased LV dP/dtmax, although heart rates were not reported in that study; the combination of IGF-I and GH, however, only mildly (but significantly) increased LV dP/dtmax. The reasons for these differences are unclear, since IGF-I levels increased further in the combination group in that study (6), as in the present experiments, although differences in heart rate responses (unreported) from those in the present study could have played a role. The mechanism for the enhanced contractility due to GH or IGF-I has not been clarified, although recent studies in the rat have suggested that increased responsiveness to calcium coupled with the hypertrophic effect may be involved (25).

Gene Expression in IGF-I/GH-Induced Hypertrophy Compared With That in Overloaded Hearts

The pattern of gene expression differed in the LV in the IGF-I/GH group from that due to pressure overload (TAC) and volume overload (AV fistula). The Northern blots in these three groups compared with those in sham-operated mice (Figs. 4 and 5) showed that pressure overload caused marked reexpression of mRNA for the genes of the embryonic gene program (ANF and alpha -skeletal actin), as previously demonstrated in pressure-overload mouse (21) and rat (12, 17, 24) hearts. Collagen III mRNA also was increased in our study, as reported previously by others in rats with pressure overload (28), whereas SERCA and phospholamban mRNA were slightly reduced (NS) compared with controls. SERCA was not significantly lowered, as reported in previous studies with pressure-overload hypertrophy in the rat (7). The pattern of gene expression with volume overload resembles in part that with IGF-I/GH in that neither ANF nor alpha -skeletal actin mRNA were increased, although, as in pressure overload, collagen III mRNA was significantly elevated with volume overload. In rats, Calderone et al. (2), using suprarenal aortic constriction or aortocaval fistula, reported large increases in preproANF mRNA at 7 days in both pressure and volume overload, whereas alpha -skeletal actin was increased only in pressure overload as in our study. Whether the difference in ANF expression in volume overload in that study (2) compared with the present experiment is due to different durations of the study (mice were studied at 14 days) or species differences is uncertain. Their finding in rats of a difference in alpha -skeletal actin mRNA expression between pressure and volume overload with similar ANF suggested separate genetic regulation of these two fetal genes (2), although in our study both were induced only by pressure overload. In volume overload, we found phospholamban mRNA to be increased compared with controls (Fig. 5), a finding previously reported in hyperthyroid rats (13). SERCA mRNA was not changed in any group, as reported previously in overload hypertrophy, although the concentration can be reduced in severe hypertrophy (7).

In conclusion, large doses of IGF-I and GH alone were not sufficient for a cardiac trophic effect in the mouse, but they acted synergistically in combination to produce substantial cardiac hypertrophic and positive inotropic effects. Cardiac hypertrophy and increased contractility together with a relatively normal pattern of mRNA expression, aside from elevated SERCA mRNA, have also been produced by thyroid administration in normal rats (22) without change in collagen gene expression (32), and this response probably reflects a relatively physiological form of hypertrophy. The current data, together with our previous findings on the rat (9), suggest that the cardiac response to IGF-I/GH may represent a relatively benign or nonpathological form of LV hypertrophy. However, the trend for collagen III to be increased in the IGF-I/GH group (P = 0.10 vs. controls) does not allow exclusion of the possibility that abnormal gene expression can be induced by growth factors, and further studies on this issue are needed.

    ACKNOWLEDGEMENTS

The authors thank Dr. Francisco Villarreal for the cDNA probe for collagen III, Carol Kent for mRNA determinations, Farid Abdel-Wahhab for technical assistance, and Pamela Alford for manuscript preparation.

    FOOTNOTES

This study was supported in part by National Heart, Lung, and Blood Institute Specialized Center of Research Grant HL-53733, the Richard D. Winter Fund, and an endowed chair of the American Heart Association, California Affiliate, San Diego County Division (J. Ross, Jr.).

Present addresses: N. Tanaka, Shimonoseki-City Ishikai Hospital, 1-2 Daigakucho 2-Chome, Shimonoseki, Yamaguchi 751, Japan; R. G. Clark, Research Centre for Developmental Medicine and Biology, School of Medicine, University of Auckland, Private Bag 92019, Auckland, New Zealand.

Address for reprint requests: J. Ross, Jr., Dept. of Medicine 0613B, University of California, San Diego, 9500 Gilman Dr., La Jolla, CA 92093-0613.

Received 19 November 1997; accepted in final form 9 April 1998.

    REFERENCES
Top
Abstract
Introduction
Methods
Results
Discussion
References

1.   Amato, G., C. Carella, S. Fazio, G. La Montagna, A. Cittadini, D. Sabatini, C. Marciano-Mone, L. Sacca, and A. Bellastella. Body composition, bone metabolism, and heart structure and function in growth hormone (GH)-deficient adults before and after GH replacement therapy at low doses. J. Clin. Endocrinol. Metab. 77: 1671-1676, 1993[Abstract].

2.   Calderone, A., N. Takahasi, N. J. Izzo, Jr., C. Thaik, and W. S. Colucci. Pressure- and volume-induced left ventricular hypertrophies are associated with distinct myocyte phenotypes and differential induction of peptide growth factor mRNAs. Circulation 92: 2385-2390, 1995[Abstract/Free Full Text].

3.   Celniker, A. C., A. B. Chen, R. M. Wert, Jr., and B. M. Sherman. Variability in the quantitation of circulating growth hormone using commercial immunoassays. J. Clin. Endocrinol. Metab. 68: 469-476, 1989[Abstract].

4.   Chien, K. R., K. U. Knowlton, H. Zhu, and S. Chien. Regulation of cardiac gene expression during myocardial growth and hypertrophy: molecular studies of an adaptive physiologic response. FASEB J. 5: 3037-3046, 1991[Abstract].

5.   Cittadini, A., A. Cuocolo, B. Merola, S. Fazio, D. Sabatini, E. Nicolai, A. Colao, S. Longobardi, G. Lombardi, and L. Saccà. Impaired cardiac performance in GH-deficient adults and its improvement after GH replacement. Am. J. Physiol. 267 (Endocrinol. Metab. 30): E219-E225, 1994[Abstract/Free Full Text].

6.   Cittadini, A., H. Strömer, S. E. Katz, R. Clark, J. P. Morgan, and P. S. Douglas. Differential cardiac effects of growth hormone and insulin-like growth factor-I in the rat. A combined in vivo and in vitro evaluation. Circulation 93: 800-809, 1996[Abstract/Free Full Text].

7.   De la Bastie, D., Levitsky, L. Rappaport, J. J. Mercadier, F. Marotte, C. Wisnewsky, V. Brovkovich, K. Schwartz, and A. N. Lompré. Function of the sarcoplasmic reticulum and expression of its Ca2+-ATPase gene in pressure overload-induced cardiac hypertrophy in the rat. Circ. Res. 66: 554-564, 1990[Abstract/Free Full Text].

8.   Donath, M. Y., R. Jenni, H. P. Brunner, M. Anrig, S. Kohli, Y. Glatz, and E. R. Froesch. Cardiovascular and metabolic effects of insulin-like growth factor I at rest and during exercise in humans. J. Clin. Endocrinol. Metab. 81: 4089-4094, 1996[Abstract/Free Full Text].

9.   Duerr, R. L., S. Huang, H. R. Miraliakbar, R. Clark, K. R. Chien, and J. Ross, Jr. Insulin-like growth factor-I enhances ventricular hypertrophy and function during the onset of experimental cardiac failure. J. Clin. Invest. 95: 619-627, 1995.

10.   Furlanetto, R. W., L. E. Underwook, J. J. Van Wyk, and A. J. D'Ercole. Estimation of somatomedin-C levels in normals and patients with pituitary disease by radioimmunoassay. J. Clin. Invest. 60: 648-657, 1977.

11.   Hunter, J. J., N. Tanaka, H. A. Rockman, J. Ross, Jr., and K. R. Chien. Ventricular expression of a MLC-2v-Ras fusion gene induces cardiac hypertrophy and selective diastolic dysfunction in transgenic mice. J. Biol. Chem. 270: 23173-23178, 1995[Abstract/Free Full Text].

12.   Izumo, S., B. Nadal-Ginard, and V. Mahdavi. Protooncogene induction and reprogramming of cardiac gene expression produced by pressure overload. Proc. Natl. Acad. Sci. USA 85: 339-343, 1988[Abstract/Free Full Text].

13.   Kiss, E., G. Jakab, E. G. Kranias, and I. Edes. Thyroid hormone-induced alterations in phospholamban protein expression. Regulatory effects on sarcoplasmic reticulum Ca2+ transport and myocardial relaxation. Circ. Res. 75: 245-251, 1994[Abstract/Free Full Text].

14.   Kupfer, S. R., L. E. Underwood, R. C. Baxter, and D. R. Clemmons. Enhancement of the anabolic effects of growth hormone and insulin-like growth factor I by use of both agents simultaneously. J. Clin. Invest. 91: 391-396, 1993.

15.   Lei, L.-Q., S. Rubin, and M. C. Fishbein. Cardiac architectural changes with hypertrophy induced by excess growth hormone in rats. Lab. Invest. 59: 357-362, 1988[Medline].

16.   Little, W. C. The left ventricular dP/dtmax-end-diastolic volume relation in closed-chest dogs. Circ. Res. 56: 808-815, 1985[Abstract/Free Full Text].

17.   Mercadier, J. J., J. L. Samuel, J. B. Michel, M. A. Zongazo, D. de la Bastie, A. M. Lompre, C. Wisnewsky, L. Rappaport, B. Levy, and K. Schwartz. Atrial natriuretic factor gene expression in rat ventricle during experimental hypertension. Am. J. Physiol. 257 (Heart Circ. Physiol. 26): H979-H987, 1989[Abstract/Free Full Text].

18.   Merez, M. A., M. White, K. C. F. Sheehan, E. A. Bach, S. J. Rodig, A. S. Dighe, D. H. Kaplan, J. K. Riley, A. C. Greenlund, D. Campbell, K. Carver-Moore, R. N. DuBois, R. Clark, M. Aguet, and R. D. Schreiber. Targeted disruption of the Stat1 gene in mice reveals unexpected physiologic specificity in the JAK-STAT signaling pathway. Cell 84: 431-442, 1997.

19.   Milano, C. A., L. F. Allen, H. A. Rockman, P. C. Dolber, T. R. McMinn, K. R. Chien, T. D. Johnson, R. A. Bond, and R. J. Lefkowitz. Enhanced myocardial function in transgenic mice overexpressing the beta 2-adrenergic receptor. Science 264: 582-586, 1994[Abstract/Free Full Text].

20.   Palakodeti, V., S. Oh, B. H. Oh, L. Mao, M. Hongo, K. L. Peterson, and J. Ross, Jr. The force-frequency effect is a powerful determinant of myocardial contractility. Am. J. Physiol. 273 (Heart Circ. Physiol. 42): H1283-H1290, 1997[Abstract/Free Full Text].

21.  Rockman, H. A., K. U. Knowlton, A. Harris, J. Ross, Jr., and K. R. Chien. In vivo murine cardiac hypertrophy: a novel model to identify genetic signaling mechanisms that activate an adaptive physiologic response. Circulation 87, Suppl. VII: VII-14-VII-21, 1993.

22.   Rohrer, D., and W. H. Dillmann. Thyroid hormone markedly increases the mRNA coding for sarcoplasmic reticulum Ca2+-ATPase in the rat heart. J. Biol. Chem. 263: 6941-6944, 1988[Abstract/Free Full Text].

23.  Scheuer, J., and P. Buttrick. The cardiac hypertrophic responses to pathologic and physiologic loads. Circulation 75, Suppl. I: I-63-I-68, 1987.

24.   Schwartz, K., D. de la Bastie, P. Bouveret, P. Oliviéro, S. Alonso, and M. Buckingham. alpha -Skeletal muscle actin mRNA's accumulate in hypertrophied adult rat hearts. Circ. Res. 59: 551-555, 1986[Abstract/Free Full Text].

25.   Strömer, H., A. Cittadini, P. S. Douglas, and J. P. Morgan. Exogenously administered growth hormone and insulin-like growth factor-I alter intracellular Ca2+ handling and enhance cardiac performance. In vitro evaluation in the isolated isovolumic buffer-perfused rat heart. Circ. Res. 79: 227-236, 1996[Abstract/Free Full Text].

26.   Tanaka, N., N. Dalton, H. A. Rockman, K. L. Peterson, J. J. Hunter, K. R. Chien, and J. Ross, Jr. Transthoracic echocardiography in the normal and abnormal mouse heart. Circulation 94: 1109-1117, 1997[Abstract/Free Full Text].

27.   Thuesen, L., J. S. Christiansen, K. E. Sorensen, J. O. L. Jorgensen, H. Orskov, and P. Henningsen. Increased myocardial contractility following growth hormone administration in normal man. An echocardiographic study. Dan. Med. Bull. 35: 193-196, 1988[Medline].

28.   Villarreal, R. J., and W. H. Dillmann. Cardiac hypertrophy-induced changes in mRNA levels for TGF-beta 1, fibronectin, and collagen. Am. J. Physiol. 262 (Heart Circ. Physiol. 31): H1861-H1866, 1992[Abstract/Free Full Text].

29.   Wangler, R. D., K. G. Peters, M. L. Marcus, and R. J. Tomanek. Effects of duration and severity of arterial hypertension and cardiac hypertrophy on coronary vasodilator reserve. Circ. Res. 51: 10-18, 1982[Abstract/Free Full Text].

30.   Weber, K. T., and C. G. Brilla. Pathological hypertrophy and cardiac interstitium. Fibrosis and renin-angiotensin-aldosterone system. Circulation 83: 1849-1865, 1991[Abstract/Free Full Text].

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

32.   Yao, J., and M. Eghbali. Decreased collagen gene expression and absence of fibrosis in thyroid hormone-induced myocardial hypertrophy. Response of cardiac fibroblasts to thyroid hormone in vitro. Circ. Res. 71: 831-839, 1992[Abstract/Free Full Text].

33.   Yin, F. C., H. A. Spurgeon, K. Rakusan, M. L. Weisfeldt, and E. G. Lakatta. Use of tibial length to quantify cardiac hypertrophy: application in the aging rat. Am. J. Physiol. 243 (Heart Circ. Physiol. 12): H941-H947, 1982[Abstract/Free Full Text].

34.   Zapf, J., H. Walter, and E. R. Froesch. Radioimmunological determination of insulin-like growth factors I and II in normal subjects and in patients with growth disorders and extrapancreatic tumor hypoglycemia. J. Clin. Invest. 68: 1321-1330, 1981.

Am J Physiol Heart Circ Physiol 275(2):H393-H399
0002-9513/98 $5.00 Copyright © 1998 the American Physiological Society


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