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(Circulation. 2002;105:975.)
© 2002 American Heart Association, Inc.
Basic Science Reports |
From the First Department of Internal Medicine, Fukushima Medical University, Fukushima, Japan.
Correspondence to Yukio Maruyama, MD, First Department of Internal Medicine, Fukushima Medical University, Hikarigaoka 1, Fukushima, 960-1295, Japan. E-mail maruyama{at}fmu.ac.jp
| Abstract |
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Methods and Results We administered a vehicle, carvedilol, propranolol (2, 10, and 30 mg/kg per day, each), metoprolol (6, 30, and 90 mg/kg per day), or bunazosin (0.2 and 1 mg/kg per day), orally for 12 weeks to a total of 608 rats with CS or CO. In these groups and the sham (n=40), we assessed LV function by echocardiography, CS severity, myocardial blood flow and coronary flow reserve, serum ascorbyl free radical, and vitamin C. Both CS and CO increased LV end-diastolic and end-systolic diameters and decreased ejection fraction. The 4 agents failed to attenuate LV remodeling caused by CO. In contrast, the 3 ß-blockers attenuated (P<0.01) or tended to attenuate the increase in LV end-diastolic diameters caused by CS. With similar blood pressure and heart rate lowering by 3 ß-blockers, carvedilol additionally attenuated the increase in end-systolic diameters and improved ejection fraction. The CS reduced myocardial blood flow and coronary flow reserve, which was reversed by carvedilol without modifying the CS severity. Among the 4 agents, only carvedilol decreased ascorbyl free radical and increased vitamin C.
Conclusions The effects of ß blockade on ischemic cardiac dysfunction seem to depend on the different properties of the ß-blockers and the doses used. Among the ß-blockers tested, carvedilol provided potent cardioprotection for compromised ischemic but viable myocardium rather than for infarcted myocardium.
Key Words: stenosis infarction remodeling receptors, ardrenergic, beta ischemia
| Introduction |
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Carvedilol, a ß antagonist, improves the prognosis and prevents the progression of LV remodeling and dysfunction in heart failure of nonischemic origin.3 In heart failure of ischemic origin, carvedilol reduces cardiac events,4 attenuates cardiac dysfunction,5 and reduces mortality6 in acute infarction followed by reperfusion. However, it remains to be determined whether carvedilol attenuates LV remodeling or dysfunction associated with coronary stenosis. The present study was undertaken to assess whether carvedilol attenuates LV dysfunction and remodeling induced by chronic coronary stenosis as well as by coronary occlusion. In addition, to see whether the effects of carvedilol are attributable solely to lowering the heart rate (HR) and systolic blood pressure (SBP) or whether a blocking effect or antioxidant property may also be involved, the effects of propranolol, metoprolol, and bunazosin were also assessed in the same animal models.
| Methods |
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Animals
Adult male Sprague-Dawley rats (290 to 310 g; n=699; CLEA Japan, Inc, Tokyo, Japan) were anesthetized by intraperitoneal 30 mg/kg sodium pentobarbital and were artificially ventilated. After a left thoracotomy (n=461, Figure 1), a stainless steel thread (275 µm in diameter) was placed on the epicardium along the left coronary artery (LCA), and the thread and LCA were ligated together followed by thread removal, as previously reported7 with minor modifications. During the brief coronary occlusion, the ST segment on ECG was elevated, and 15 animals with ST elevation persisting after thread removal were excluded from the study. In 198 animals, coronary ligation was performed at the equivalent site of the LCA, and surviving animals with persistent ST elevation (n=192) were used in the study.
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The animals were returned to their cages, fed ad libitum, and killed 12 weeks later. We discontinued the preliminary studies treated with propranolol (90 mg/kg per day) and metoprolol (270 mg/kg per day) (n=15 each) in the coronary stenosis model because of high mortality rates, and the other rats (n=648, including 40 sham rats) were divided randomly into subgroups by treatments811 (animal numbers shown in Figure 1), as follows: sham, inert vehicle administration in the coronary stenosis and occlusion models (V stenosis and occlusion groups), carvedilol administration (2, 10, and 30 mg/kg per day; C2, C10, and C30 stenosis and occlusion groups, respectively), metoprolol administration (6, 30, and 90 mg/kg per day; M6, M30, and M90 stenosis and occlusion groups, respectively), propranolol administration (2, 10, and 30 mg/kg per day; P2, P10, and P30 stenosis and occlusion groups, respectively), and bunazosin administration (0.2 and 1 mg/kg per day; B0.2 and B1 stenosis and occlusion groups, respectively). Within 24 hours after surgery, the drugs were administered daily by mouth with a cannula. The hemodynamic, echo, and microsphere studies were done 6 hours after the last administration of the drugs.
Hemodynamics in the Awake Animals
SBP and HR of awake animals were measured by the tail-cuff method before and 4, 8, and 12 weeks after surgery.
Echocardiography
Before and 6 hours (except for the sham) and 4, 8, and 12 weeks after surgery, B- and M-mode echocardiography was obtained in anesthetized rats using a 10-MHz probe and Sonos 100 equipment (Hewlett Packard). LV end-diastolic diameter (LVEDD) and end-systolic diameter (LVESD) were measured, then LV ejection fraction (LVEF) was calculated by the Pombo method. Among 648 rats, echocardiography was performed blindly in 531 and not blindly in 117.
Cardiac Catheterization
HR, LV peak systolic and end-diastolic pressures (LVSP/EDP), and positive and negative LV dP/dt were measured by cardiac catheterization in anesthetized rats 12 weeks after surgery.
Myocardial Perfusion
Twelve weeks after coronary stenosis, myocardial blood flow (MBF) (mL/min per wet g) and coronary flow reserve (CFR) (mL/min per wet g; maximal MBF by dipyridamole [10 mg/kg per min] minus basal MBF) were measured under anesthesia with colored microspheres (animal numbers shown in Figure 1). The risk areas (ischemic regions) were delineated by reoccluding the site of coronary stenosis followed by LV dye infusion at a pressure of 100 mm Hg.
Coronary Stenosis Severity
After the cardiac catheterization, rats (animal numbers shown in Figure 1) were sacrificed and fixed with 10% neutral buffered formalin perfused at a pressure of 100 mm Hg. In 5-µm-thick paraffin-embedded sections stained with elastica Van Gieson, cross-sectional areas (CSA) of LCA inner lumen were measured by the point-counting method of Weibel12 by light microscopy at x400 magnification. The CSA at the stenotic site divided by the reference CSA located 50 sections proximal to the sections of stenotic area multiplied by 100 was considered the degree (%) of stenosis.
Blood Samples
Blood samples were obtained from all rats of the groups (except rats for the microsphere study) at the time of cardiac catheterization. Plasma norepinephrine levels were measured by HPLC. Thiobarbituric acid reactive substance (TBARS) by fluorescence spectroscopy, ascorbyl free radical (AFR) (signal intensities relative to the standard signal intensities from manganese oxide including Mn2+ impurity) by ESR,13 and vitamin C by HPLC were measured in the sera of the sham (n=16), V (n=13), C2 (n=9), C30 (n=17), M6 (n=9), M30 (n=16), P2 (n=9), P30 (n=15), and B0.2 and B1 (n=9 each) stenosis groups (Table 1).
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Data Analysis
Data are expressed as mean±SEM. Statistical analysis was performed by the 2-way ANOVA with repeated measure. Statistics were presented in comparison with the sham, vehicle, and C30 groups (for intertreatment group comparisons). If F test results were <0.05, Scheffes post hoc test was performed. A value of P<0.01 was considered significant.
| Results |
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Hemodynamics in the Awake Animals
Because SBP and HR measured by the tail cuff were similar between 4 and 12 weeks, only the data at 12 weeks are shown in Tables 1 and 2. Both HR and SBP in the 3 ß-blocker groups and SBP alone in the bunazosin groups were decreased in a dose-dependent manner.
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Coronary Stenosis Severity, MBF, and CFR
The coronary stenosis severity (%) was similar among the 9 coronary stenosis groups examined (Table 1).
In risk areas, compared with the sham, basal MBF decreased in 10 stenosis groups but not in the C10 and C30 groups, and CFR decreased in 12 stenosis groups (Table 1). Compared with the nonrisk areas, MBF decreased in the risk areas of the V, C2, M6, M90, P2, P10, B0.2, and B1 stenosis groups and CFR decreased in all of the risk areas of 12 stenosis groups.
Echocardiography
In the coronary stenosis groups, LVEDD (Figure 2, left) and LVESD (Figure 3, left) increased and LVEF (Figure 4, left) decreased in the V group at 4 to 12 weeks compared with the sham. Among the ß blockertreated groups, compared with the V group, the increase in LVEDD was not attenuated in the C2, M6, M90, P2, and P10 groups (Figure 2, left) but was attenuated in the C10 (at 8 to 12 weeks), C30 (at 4 to 12 weeks), and M30 (at 12 weeks) groups and tended to be smaller in the P30 group (Figure 2, left). Compared with the V group, the increase in LVESD was attenuated in the C10 (at 12 weeks) and C30 (at 4 to 12 weeks) groups (Figure 3, left). Consequently, the decrease in LVEF observed in the V group was attenuated only in the C30 group at 12 weeks (Figure 4, left).
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Among the coronary occlusion groups, LVEDD (Figure 2, right) and LVESD (Figure 3, right) increased, and LVEF (Figure 4, right) decreased in all groups compared with the sham. These changes were greater than those in each treatment group with coronary stenosis (LVEDD in 11 groups except the V group and LVESD in 12 groups), and LVEDD, LVESD, and LVEF were not modulated by any treatment.
Because in the B0.2 and B1 stenosis and occlusion groups there were no significant changes in the LVEDD, LVESD, and LVEF compared with the corresponding V group at all time points measured, we show the data only at 12 weeks in these groups. LVEDD at 12 weeks was 8.1±0.2* and 7.5±0.1 mm, LVESD was 5.7±0.1* and 5.2±0.1* mm, and LVEF was 0.66±0.01* and 0.66±0.01* mm in the B0.2 and B1 stenosis groups, respectively. LVEDD at 12 weeks was 9.3±0.2* and 8.9±0.3* mm, LVESD was 7.2±0.2* and 6.8±0.2* mm, and LVEF was 0.53±0.01* and 0.56±0.01* mm in the B0.2 and B1 occlusion groups, respectively (*P<0.01 versus sham).
Cardiac Catheterization
In rats with coronary stenosis (Table 1), compared with the sham, both LVSP and HR decreased in the C30, M30, M90, and P30 groups, whereas only LVSP decreased in the C10, P10, B0.2, and B1 groups. In addition, positive or negative LV dP/dt decreased in 11 stenosis groups except in the C10 group, and LVEDP increased in 10 groups but not in the C10 and C30 groups. Compared with the V group, LVEDP decreased, and positive or negative LV dP/dt increased in the C10 and C30 groups.
In rats with coronary occlusion (Table 2), compared with sham, LVSP decreased in 7 groups (not in the V, C2, M6, P2, and B0.2 groups), HR decreased in the C30, M30, M90, P10, and P30 groups, and positive or negative LV dP/dt decreased and LVEDP increased in all 12 groups.
Heart weights were greater in the V, P2, B0.2, and B1 stenosis groups than in the sham, and those of the C30 stenosis group were lower than in the V stenosis group (Table 1). Heart weights were greater in 9 coronary occlusion groups, except for the M30, P10, and P30 groups, compared with the sham (Table 2).
Blood Substances
Plasma norepinephrine increased in 10 stenosis groups (not in the C10 and C30 groups) (Table 1) and in all 12 occlusion groups compared with sham (Table 2).
There were no differences in TBARS levels among the stenosis groups examined (Table 1). Serum AFR was higher in the stenosis groups examined, except for the C30 group compared with the sham, and was lower in the C30 stenosis group than in the V stenosis group. In contrast, serum vitamin C levels were lower in the V, M30, P2, P30, and B0.2 stenosis groups compared with the sham and were higher in the C30 stenosis group compared with the V stenosis group.
| Discussion |
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In the C10 and C30 stenosis groups, modulation of LV function and morphology is likely to be associated intimately with an increase in MBF and CFR. Because the coronary stenosis severity was similar among the 9 treatment groups examined and HR and LVSP, determinants of cardiac work, were not increased in both groups, the increases in MBF and CFR seem to be attributable to improvement of coronary microvascular dilating function. In addition, from the results with bunazosin, a significant contribution of a blockade to the effect on the C10 and C30 stenosis groups is unlikely. AFR was lower and vitamin C was higher in the C30 but not in the C2 stenosis group than in the V stenosis group. The level of AFR reflects the sum of radicals trapped by endogenous vitamin C, suggesting that the C30 treatment reduced oxygen radicals, thereby sparing the consumption of endogenous antioxidant. Thus, the antioxidant activity of carvedilol may have contributed in part to the improvement of coronary microcirculation as well as to the antiremodeling effect in our coronary stenosis model.
In the coronary occlusion model, compared with the V group, positive LV dP/dt in the C10 and C30 groups tended to increase (P<0.05), but LV remodeling was not attenuated by carvedilol. Carvedilol was reported to attenuate heart failure in which prior infarction was one of the causes.3,14 The present study indicates that carvedilol, at doses effective for coronary stenosisinduced LV dysfunction, may fail to attenuate LV dysfunction in acute infarction without reperfusion.
The antiheart failure effect of carvedilol in the coronary stenosis model was dose dependent. The C10 and C30 doses seem high when compared with human doses, suggesting that the HR- and SBP-lowering effects may be weaker in rats. Accordingly, we must be careful about the direct application of these data to clinical use.
The relative doses of ß-blockers used were not determined by objective means, such as isoproterenol challenges. We compared the effects of 3 ß-blockers at similar HR and SBP levels in the resting state. In humans,15 the greater antiheart failure effect of carvedilol than of metoprolol likely corresponded to the greater ß blocking action at peak exercise than in the resting state. Our data do not rule out the possibility that the potential differences in the ß blocking action (not reflected at resting HR and SBP) between the agents may have contributed to the different antiremodeling effects. On the other hand, it is possible that in the ß blocker groups treated with larger doses, a negative inotropic effect may have offset the improvement of LV function caused by the attenuation of ischemia. Additional studies using more precise determinations of comparable ß blocking doses will need to be performed before concluding that carvedilol has qualitatively superior antiremodeling effects in the stenosis model.
Although bunazosin significantly decreased SBP in our long-term treatment, it did not increase plasma norepinephrine levels and HR. This may not be inconsistent with a previous observation16 in which bunazosin in a short experiment did not cause reactive tachycardia, decreased renal nerve activity, and increased preganglionic adrenal nerve activity, an index of central sympathoinhibitory activity. The mechanisms of these actions of bunazosin remain to be determined.
Our study has several limitations. First, ß-blockers are used with incremental doses in humans,4 but we gave a constant dose to rats. This may have modified the drugs effect. Second, we did not assess how daily dosing in our protocol affected the pharmaceutical effects of the agents with respect to differences in half lives, counteracting ß receptor expression and postreceptor signaling.17 Third, in coronary occluded hearts, our results on the effect of metoprolol are not consistent with a previous study,10 probably partly because of different experimental design, doses, routes of drug delivery, or time of starting administration. Therefore, our results do not necessarily negate the beneficial effect of ß blockade even in the infarcted heart. Fourth, the present study does not clarify how different degrees of coronary stenosis affect LV function and remodeling with and without treatment. Fifth, 117 animals were not tested in a blind fashion in the echocardiographic study. Sixth, MBF and CFR were not measured in awake animals, so the data may not reflect those obtained with intact sympathetic activity.
| Conclusions |
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blocking action. Improvement of coronary circulation and reduction of free radicals might in part be involved in the antiremodeling effect of carvedilol. Our results show that carvedilol provides potent cardioprotection for compromised ischemic but viable myocardium rather than for infarcted myocardium | Acknowledgments |
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Received August 29, 2001; revision received December 17, 2001; accepted December 21, 2001.
| References |
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2. Adams KF, Dunlap SH, Sueta CA, et al. Relation between gender, etiology and survival in patients with symptomatic heart failure. J Am Coll Cardiol. 1996; 28: 17811788.
3. Packer M, Bristow MR, Cohn JN, et al. The effect of carvedilol on morbidity and mortality in patients with chronic heart failure: US Carvedilol Heart Failure Study Group. N Engl J Med. 1996; 334: 13491355.
4. Australia-New Zealand Heart Failure Research Group. Effects of carvedilol, a vasodilator ß-blocker, in patients with congestive heart failure due to ischemic heart disease. Circulation. 1995; 92: 212218.
5. Basu S, Senior R, Raval U, et al. Beneficial effects of intravenous and oral carvedilol treatment in acute myocardial infarction: a placebo-controlled, randomized trial. Circulation. 1997; 96: 183191.
6. Dargie HJ. Effect of carvedilol on outcome after myocardial infarction in patients with left-ventricular dysfunction: the CAPRICORN randomised trial. Lancet. 2001; 357: 13851390.
7. Capasso JM, Li P, Anversa P. Nonischemic myocardial damage induced by nonocclusive constriction of coronary artery in rats. Am J Physiol. 1991; 260: H651H661.
8. Hashimoto H, Kanda A, Hubo H, et al. Features of the acute hypotensive action of carvedilol and its ameliorating effect on myocardial ischemia. J Cardiovasc Pharmacol. 1991; 18 (suppl): S22S28.
9. Seuter F, Perzborn E, Fiedler VB, et al. Effect of BAYU3405, a new thromboxane antagonist, on sudden death in rabbits. J Lipid Mediators. 1991; 3: 283288.
10. Prabhu SD, Chandrasekar B, Murray DR, et al. ß Adrenergic blockade in developing heart failure-effects on myocardial inflammatory cytokines, nitric oxide, and remodeling. Circulation. 2000; 101: 21032109.
11. Watanabe K, Ohta Y, Nakazawa M, et al. Low dose carvedilol inhibits progression of heart failure in rats with dilated cardiomyopathy. Br J Pharmacol. 2000; 130: 148995.
12. Weibel ER. Principles and methods for morphometric study of the lung and other organs. Lab Invest. 1963; 12: 131155.
13. Nakagawa K, Kanno H, Miura Y. Detection and analyses of ascorbyl radical in cerebrospinal fluid and serum of acute lymphoblastic leukemia. Anal Biochem. 1997; 254: 3135.
14. Cohn JN, Fowler MB, Bristow MR, et al. Safety and efficacy of carvedilol in severe heart failure. The US Carvedilol Heart Failure Study Group. J Cardiac Fail. 1997; 3: 173179.
15. Metra M, Giubbini R, Nodari S, et al. Differential effects of ß blockers in patients with heart failure: a prospective, randomized, double-blind comparison of the long-term effects of metoprolol versus carvedilol. Circulation. 2000; 102: 546551.
16.
Saito H, Togashi H, Yoshioka M. A comparative study of the effects of
1-adrenoceptor antagonists on sympathetic function in rats. Am J Hypertens. 1996; 9: 160S169S.
17. Iaccarino G, Tomhave ED, Lefkowitz RJ, et al. Reciprocal in vivo regulation of myocardial G proteincoupled receptor kinase expression by ß adrenergic receptor stimulation and blockade. Circulation. 1998; 98: 17831789.
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