HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Abstract Full Text (PDF) All Versions of this Article: 288/5/H2088    most recent 00522.2003v2 00522.2003v1 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 ISI Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via ISI Web of Science (6) Citing Articles via Google Scholar Google Scholar Articles by Merkus, D. Articles by Chilian, W. M. Search for Related Content PubMed PubMed Citation Articles by Merkus, D. Articles by Chilian, W. M.

Cardiac myocytes control release of endothelin-1 in coronary vasculature

¹Experimental Cardiology, Thoraxcenter, Erasmus MC, Rotterdam, The Netherlands; and Departments of ²Physiology, ³Anesthesiology, and Surgery, Louisiana State University Health Sciences Center, New Orleans, Louisiana

Submitted 5 June 2003 ; accepted in final form 22 December 2004

	ABSTRACT

TOP ABSTRACT METHODS RESULTS DISCUSSION GRANTS REFERENCES

 
-Adrenergic vasoconstriction in the coronary circulation is mediated through -adrenoceptors on cardiac myocytes and subsequent release of endothelin, a very potent, long-lasting vasoconstrictor. Recent studies found that adult cardiac myocytes do not express the preproendothelin gene. Thus we hypothesized that -adrenoceptor stimulation on the cardiac myocytes results in the production of an endothelin-releasing factor, which stimulates the coronary vasculature to produce endothelin. We tested this hypothesis by using an in vitro model in which isolated adult rat cardiac myocytes can be stimulated with an -adrenoceptor agonist (phenylephrine). Their bathing fluid is then transferred to isolated coronary arterioles, and vasoactive responses are measured. To identify the source of endothelin, the endothelin-converting enzyme inhibitor phosphoramidon was added to either the myocytes or the isolated arterioles. Phenylephrine enhanced the vasoconstrictor properties of the myocyte bathing fluid. Administration of phosphoramidon (in either the presence or the absence of phenylephrine) to the myocytes had no effect on the vasoactive properties of the bathing fluid. In contrast, administration of phosphoramidon to the isolated arteriole before administration of the bathing fluid converted vasoconstriction to vasodilation, similar to the effect of the endothelin A receptor antagonist JKC-301, indicating that the endothelin is indeed produced by the coronary vasculature. Administration of the angiotensin type 1 receptor antagonist losartan to the vessel bath enhanced vasodilation to the bathing fluid of the phenylephrine-treated but not control myocytes. In conclusion, during -adrenergic activation cardiac myocytes release a factor, probably angiotensin II, that stimulates the vascular production of endothelin. Although the physiological implications of this mechanism are not obvious, this may represent a protective mechanism that integrates neuronal vasoconstrictor mechanisms with myocardial metabolism, which minimizes periods of both coronary underperfusion and overperfusion.

coronary circulation; coronary microcirculation; coronary blood flow; vasoconstriction

The sympathetic nervous system may play an important role in matching myocardial oxygen supply to myocardial oxygen demand through the influence of norepinephrine release from the terminal nerve endings on the coronary vasculature. Norepinephrine can cause -adrenergic vasoconstriction as well as -adrenergic vasodilation in various species (1, 3, 7, 8, 14). In previous studies (20), we showed that, unlike in other organs, ₁-adrenergic constriction in the coronary circulation is not mediated via activation of ₁-adrenoceptors on the vascular myocytes. Rather, the ₁-adrenoceptor agonists activate the receptor on cardiac myocytes, and the resulting coronary constriction is mediated through endothelin-1 (1, 20). On the basis of these observations, we formulated the following concept: activation of ₁-adrenoceptors on the cardiac myocytes causes release of endothelin-1, which diffuses to the vasculature and causes constriction.

However, this conclusion is challenged by the observation that adult cardiac myocytes do not express the gene for preproendothelin, the precursor peptide for endothelin (17). Moreover, direct measurement of endothelin-1 concentration in the supernatant of phenylephrine-treated myocytes yielded concentrations below the vasoactive threshold (20).

We therefore proposed a revised hypothesis: cardiac myocytes produce an endothelin-releasing factor, and the release of this factor occurs during ₁-adrenergic stimulation of cardiac myocytes, which induces endothelin release by vascular endothelial cells. The aim of this study was to test these hypotheses by determining the source of endothelin released during ₁-adrenergic stimulation.

	METHODS

TOP ABSTRACT METHODS RESULTS DISCUSSION GRANTS REFERENCES

 
Studies were performed in accordance with the "Guiding principles in the Care and Use of Laboratory Animals" as approved by the Council of the American Physiological Society and with the approval of the Animal Care Committee of our institutions. Male Wistar rats (175–250 g, Harlan Sprague Dawley) were anesthetized with pentobarbital sodium (75 mg/kg ip) and decapitated. The thorax was opened, and the heart was removed and placed in ice-cold physiological saline solution (PSS). The hearts were then used for either dissection of coronary arterioles or isolation of cardiac myocytes.

Isolation of cardiac myocytes. Myocytes were isolated with a modified Langendorff setup (16). In brief, the heart was perfused with buffer containing (in mM) 123 NaCl, 2.6 KCl, 1.2 KH₂PO₄, 1.2 MgSO₄·7H₂O, 25 HEPES, 11 glucose, 20 taurine, 20 creatine, and 1 CaCl₂ (pH 7.4) for 3 min, after which the buffer was replaced by a buffer with the same composition except without the calcium for 6 min. Unless otherwise mentioned, all drugs were obtained from Sigma. Collagenase (type II, 0.6 mg/ml; Worthington) and CaCl₂ (30 µM) were then added, and the heart was perfused for another 15 min. The heart was then cut into small pieces and resuspended in perfusion buffer to which BSA (1%) was added. After 5 min, during which the suspension was gently triturated, the buffer containing the myocytes was filtered through surgical gauze to remove big clumps of myocytes and gently spun down. Calcium was reintroduced to the myocytes in a stepwise manner (200 µM, 500 µM, and 1 mM CaCl₂). The myocytes were allowed to settle under gravity in between the CaCl₂ steps. The supernatant was removed, and the pellet was resuspended in buffer containing more calcium. Because rod-shaped living cells settle faster than dead cells, this increased the percentage of viable cells in the suspension. Dead cells were identified as cells that were round in shape, whereas healthy cells were rod shaped. Only preparations containing at least 70% rod-shaped cells were used.

Dissection of coronary arterioles. Single arterioles (40- to 130-µm passive diameter) were dissected from the left ventricular free wall or the septum of the rat heart, as previously described for other species (10), and placed in ice-cold PSS of the following composition (in mM): 145.0 NaCl, 4.7 KCl, 2.0 CaCl₂, 1.17 MgSO₄, 1.2 NaH₂PO₄, 5.0 glucose, 2.0 pyruvate, 0.02 EDTA, and 3.0 MOPS, buffered to pH 7.4 at 4°C and filtered (dissection buffer). The heart was placed under a dissection microscope in a 4°C chamber, and vessels were carefully dissected free from the surrounding myocardial tissue and placed in dissection buffer containing 1% BSA (USB-Amersham). The vessels were cannulated on both ends with micropipettes (20- to 60-µm outer diameter, depending on the size of the vessel) connected to pressurized reservoirs filled with PSS buffered to pH 7.4 at 37°C. The height of these reservoirs was set to obtain the desired intraluminal pressure (60 mmHg). Vessels that failed to maintain pressure were excluded from analysis. Internal diameter of coronary microvessels was measured under a charge-coupled device camera (Sony CCD-IRIS) with a videocaliper system. The vessel was slowly warmed up to 37°C and allowed to develop spontaneous tone.

Detection of mRNA transcripts with RT-PCR. To demonstrate the source of endothelin in cardiac and coronary arterioles, we used RT-PCR. Enzymatically isolated cardiac myocytes were selected from three different batches according to a recently described method (16), to ensure that only mRNA from these cells was analyzed. In addition, mRNA was extracted from isolated coronary arterioles. RT-PCR was performed to investigate the presence of mRNA for preproendothelin, troponin T, and GAPDH. mRNA was isolated with a kit from Dynal, according to the manufacturer's instructions. Briefly, samples were sonicated in a Tris·HCl-LiCl buffer in the presence of RNase inhibitors to liberate RNA. Samples were then incubated with 30-µm magnetic beads coated with polythymidine linkers, which bind specifically and with high avidity to the polyadenylate tail of mRNA. After 15 min of incubation to allow binding of mRNA, the beads were pelleted in a magnetic precipitator and the supernatant was removed. The beads and mRNA were resuspended in extraction buffer, and the mRNA was converted to cDNA with a First Strand Ready-To-Go Beads kit (Pharmacia Biotech) according to the manufacturer's instructions. To compare expression of individual genes, cDNA was incubated with specific primers (Operon) and GIBCO PCR Supermix and cycled in a PerkinElmer thermocycler (35 cycles of 30 s at 95°C, 30 s at 55°C, 45 s at 72°C, followed by 7-min elongation at 72°C). The PCR was performed in duplicate. PCR primers for endothelial NO synthase (eNOS, endothelial cell marker; Ref. 21), endothelin-1, troponin T (cardiac myocyte marker), and -actin (marker for both endothelial cells and cardiac myocytes) were designed with Primer Picker from rat sequences obtained from GenBank. The sequences for the primer sets were -actin: sense 5'-gtc gta cca ctg gca ttg tg-3', antisense 5'-ctc tca gct gtg gtg gtg aa-3'; endothelin-1: sense 5'-gcg tcc ttg ttc caa aca tt-3'; antisense 5'-gcc tga gtc aga cac gaa ca-3'; eNOS: sense 5'-tga ccc tca ccg ata caa ca-3', antisense 5'-ctg gcc ttc tgc tca ttt tc-3'; and troponin T: sense 5'-cct gca gga aaa gtt caa gc-3', antisense 5'-gtg cct ggc aag acc tag ag-3'.

Protocol. Cardiac myocytes were incubated in the presence and absence of the ₁-adrenoceptor agonist phenylephrine (50 µM; Ref. 20) and the endothelin-converting enzyme inhibitor (phosphoramidon, 10 µM). We showed previously (20) that the response to this dose of phenylephrine can be blocked with prazosin and is therefore ₁-adrenoceptor mediated. The production of vasoactive factors by the isolated myocytes was measured in a bioassay by withdrawing supernatant from the myocyte suspension, which was then added to the isolated arterioles to establish effects on diameter (12) . Aliquots of myocyte supernatant (100, 200, and 500 µl) were added to the vessel bath (vol 4 ml). Vascular diameter was measured 5 min after addition of the supernatant and after 10 min of washout. The addition of the supernatant was repeated in the presence of the endothelin A receptor antagonist JKC-301 (5 µM; American Peptide), the angiotensin AT-1 receptor antagonist losartan (1 µM), and the endothelin-converting enzyme inhibitor phosphoramidon (10 µM)

Data analysis and statistics. All statistic analyses were performed with StatView software for the Macintosh (Abacus Concepts, Berkeley, CA). Data were compared with ANOVA for repeated measures (dose of supernatant) with Scheffé's test as post hoc multiple-comparison test. Vascular diameters are normalized to the diameter with tone, before administration of the supernatant. Data are presented as means ± SE. Significance was accepted at P < 0.05 in all experiments.

	RESULTS

TOP ABSTRACT METHODS RESULTS DISCUSSION GRANTS REFERENCES

 
Vasoactive properties. Supernatant of cardiac myocytes was added to isolated coronary arterioles, and their response was measured. Similar to results obtained in the canine circulation (20), treatment of myocytes with the ₁-adrenoceptor agonist phenylephrine (50 µM) increased the vasoconstrictor properties of the myocyte supernatant (Fig. 1), whereas treatment of the coronary arterioles with phenylephrine in this concentration had no effect (data not shown). Administration of the endothelin A receptor antagonist JKC-301 to the coronary arterioles increased the vasodilator properties of the supernatant, indicating that dilation of the vessels was limited by the presence of endothelin-1.

View larger version (13K): [in this window] [in a new window]   Fig. 1. Dilation of coronary arterioles to myocyte supernatant (n = 8) was dose dependent. Stimulation of the 1-adrenoceptor with phenylephrine (PE, 50 µM; n = 8) converted vasodilation to the supernatant into vasoconstriction. Administration of the endothelin A receptor antagonist JKC-301 (5 µM; n = 6) to the coronary arterioles increased the vasodilator properties of the myocyte supernatant, indicating that endothelin limits the dilation to the myocyte supernatant. *P < 0.05 vs. control.

View larger version (31K): [in this window] [in a new window]   Fig. 2. Ethidium bromide signals of products from RT-PCR (35 cycles) for -actin (-act), cardiac troponin T (trop), endothelial NO synthase (eNOS), and endothelin-1 (ET-1) for transcripts isolated from enzymatically isolated cardiac myocytes (M) and whole heart (H). One hundred-base pair ladders were run on both sides of the gel. Note that products from -actin and troponin were robust in both preparations but the signals from eNOS and ET-1 were observed only in transcripts from the whole heart and were absent in the myocyte preparations.

View larger version (16K): [in this window] [in a new window]   Fig. 3. Administration of phosphoramidon (Phos, 10 µM), an inhibitor of endothelin-converting enzyme, to the myocytes did not affect dilation of the vessels to the supernatant of quiescent myocytes (n = 6 with and without Phos) or PE-treated myocytes (50 µM; n = 5 with and without Phos). *P < 0.05 vs. control.

View larger version (16K): [in this window] [in a new window]   Fig. 4. Administration of Phos (10 µM), an inhibitor of endothelin-converting enzyme, to the vessels increased their dilation to the supernatant of both quiescent myocytes (n = 6, with and without Phos) and PE (50 µM; n = 5, with and without Phos)-treated myocytes. *P < 0.05 vs. control; P < 0.05 vs. PE; P < 0.05 effect of Phos is different from control.

View larger version (14K): [in this window] [in a new window]   Fig. 5. Angiotensin type 1 receptor blockade (losartan, 1 µM; n = 4 in all protocols) on the coronary arterioles did not affect the vasodilator properties of the myocyte supernatant, whereas endothelin receptor blockade did increase the dilation, indicating that angiotensin II is not the endothelin-releasing factor in our preparation. *P < 0.05 vs. control.

View larger version (11K): [in this window] [in a new window]   Fig. 6. Angiotensin type 1 receptor blockade (losartan, 1 µM) on the coronary arterioles did not increase vasodilation to control myocyte supernatant (500 µl; n = 4, paired data, left), whereas it increased vasodilation to supernatant of myocytes treated with PE (50 µM; n = 5, paired data, right). *P < 0.05 vs. supernatant without PE; P < 0.05 vs. supernatant without losartan.

	DISCUSSION

TOP ABSTRACT METHODS RESULTS DISCUSSION GRANTS REFERENCES

Methodological considerations. We used an in vitro system to investigate the control of endothelin production by studying enzymatically isolated cardiac myocytes and isolated coronary arterioles (12). A potential problem is that enzymatic isolation may damage or even kill the cells. We minimized the problem of dead cells by using only preparations with >70% rod-shaped cells. There is the possibility that dead cells may release vasoactive substances, which could complicate our findings. However, supernatant from preparations with mainly dead cells (80%) was not vasoactive (data not shown). Therefore, we believe that the responses to the supernatant involve vasoactive substances released by the viable cardiac myocytes.

The main advantage of our in vitro system is that we can distinguish between production of factors by cardiac myocytes and vascular cells. This is important for unequivocal identification of the source of endothelin. Within this context, two separate experiments identify the vasculature as the source of endothelin. First, the RT-PCR results show that the gene for preproendothelin, the precursor of endothelin, is not expressed in adult cardiac myocytes, which is in accordance with a study from Preisig-Muller et al. (17). Second, administration of the endothelin-converting enzyme inhibitor separately to both cardiac myocytes and coronary arterioles allowed us to identify the vasculature as the source of endothelin. Interestingly, the cardiac myocytes released a factor, which may be angiotensin II, that stimulates the vascular production of endothelin. Additionally, many substances are both vasoactive and cardioactive, because their receptors are present both on vascular and cardiac myocytes. With our system, we can block the receptors on the vasculature without affecting the myocytes and vice versa. This is especially important for the endothelin A receptor, which, when stimulated, causes vasoconstriction as well as an increase in inotropy of the myocytes (in both humans and rats; Ref. 4), which in turn may increase the production of vasodilators and increase extravascular compression. Thus administration of an endothelin A receptor antagonist in vivo also has indirect effects on the vasculature and may therefore result in overestimation of the true vascular effects of endothelin-1 when tested in vivo.

Implications of findings. Quiescent cardiac myocytes produce factors that stimulate the production of endothelin in coronary arterioles, which increases coronary vascular tone. The production of these factors is controlled by cardiac metabolism (12) as well as by the sympathetic nervous system, through the -adrenoceptor. -Adrenergic vasoconstriction has been proposed to prevent excessive backflow from the coronary circulation, thereby promoting subendocardial perfusion. Through production of vasoconstrictors, cardiac myocytes are capable of increasing basal coronary resistance to prevent excess myocardial perfusion.

Conventionally, the dogma for coronary control is that the production of an unknown vasodilator(s) is directly coupled to myocardial oxygen consumption. Thus at low levels of myocardial oxygen consumption reduced production of vasodilator(s) is associated with augmented coronary tone. However, our results challenge this dogma by suggesting that the enhanced production of a constrictor at low levels of myocardial oxygen consumption increases coronary tone. Perhaps a system that utilizes two opposing control schemes (dilators vs. constrictors) can more quickly adjust to alterations in metabolism than one that simply titrates flow to altered production of vasodilators. In accordance with this theory, we recently showed (12) that, when an increase in myocardial oxygen consumption occurs, flow can be increased both by augmented production of vasodilators and by concomitant reduction in the production of endothelin. Moreover, recent experiments by Winegrad et al. showed that myocytes can act as oxygen sensors in the heart, producing a vasodilator when oxygen tension decreases and a constrictor when oxygen tension increases. In that study, the constrictor involved was identified as angiotensin, which caused endothelin-mediated constriction (23). In our experiments with supernatant from quiescent myocytes the endothelin-releasing factor did not seem to be angiotensin II, because administration of losartan to the coronary arterioles did not alter the vasoactive properties of the supernatant. Surprisingly, when the myocytes were stimulated with phenylephrine, the vasoconstriction of the coronary arterioles to the supernatant was reversed by losartan, indicating that phenylephrine-stimulated myocytes do release angiotensin II. Yet inhibition of endothelin-converting enzyme in the coronary arterioles converts vasoconstriction to supernatant of phenylephrine-treated myocytes to vasodilation. Thus, even after angiotensin receptor blockade, there may still be some vascular endothelin production. Apparently, there are two factors that can be released from cardiac myocytes, one of them being angiotensin II, that induce endothelin production in the coronary vasculature.

An advantage of endothelin production in the endothelium is that the endothelium directly senses changes in shear stress and thus can provide a feedback system if vasoconstriction is too intense. Vasoconstriction will result in an increase in shear stress, thereby increasing the production of NO, which then limits the vasoconstriction through its vasodilator action on vascular smooth muscle (19). Also, NO limits the production and release of endothelin by the endothelium (11). Thus NO provides a negative feedback mechanism to limit excess vasoconstriction induced by endothelin.

Clinically, our findings are important in patients with heart failure. Heart failure results in increased sympathetic nervous system activity (18), aimed at maintaining blood pressure, through an increase in heart rate and peripheral vasoconstriction, to ensure adequate perfusion of the brain. However, the enhanced sympathetic stimulation of the cardiac myocytes will also result in enhanced endothelin production by the coronary vasculature. Moreover, because heart failure is often accompanied by endothelial dysfunction, NO production is decreased, which may result in inadequate negative feedback on vascular endothelin production. Thus coronary blood supply may be limited by an increased endothelin-induced vasoconstriction, while myocardial oxygen demand is increased because of the increased workload of the heart (increased heart rate as well as increased peripheral resistance).

In conclusion, because endothelin is a very potent and long-lasting vasoconstrictor, its production and release need to be carefully regulated. The prime site of production of endothelin in the heart is the coronary vasculature, but endothelin production is regulated based on signals obtained from the cardiac myocytes.

	GRANTS

TOP ABSTRACT METHODS RESULTS DISCUSSION GRANTS REFERENCES

 
We gratefully acknowledge support from the American Heart Association (Grant 9920433Z), the National Heart, Lung, and Blood Institute (Grants HL-32788 and HL-65203), as well as the Netherlands Heart Foundation (Grant 2000T042).

	FOOTNOTES

 

Address for reprint requests and other correspondence: D. Merkus, Experimental Cardiology, Thoraxcenter, Erasmus MC, University Medical Center Rotterdam, PO Box 1738, 3000 DR Rotterdam, The Netherlands (E-mail: d.merkus{at}erasmusmc.nl)

The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

	REFERENCES

TOP ABSTRACT METHODS RESULTS DISCUSSION GRANTS REFERENCES

 

1. DeFily DV, Nishikawa Y, and Chilian WM. Endothelin antagonists block ₁-adrenergic constriction of coronary arterioles. Am J Physiol Heart Circ Physiol 276: H1028–H1034, 1999.[Abstract/Free Full Text]
2. Duncker DJ and Bache RJ. Regulation of coronary vasomotor tone under normal conditions and during acute myocardial hypoperfusion. Pharmacol Ther 86: 87–110, 2000.[CrossRef][ISI][Medline]
3. Duncker DJ, Stubenitsky R, and Verdouw PD. Autonomic control of vasomotion in the porcine coronary circulation during treadmill exercise: evidence for feed-forward -adrenergic control. Circ Res 82: 1312–1322, 1998.[Abstract/Free Full Text]
4. Ergul A. Endothelin-1 and endothelin receptor antagonists as potential cardiovascular therapeutic agents. Pharmacotherapy 22: 54–65, 2002.[CrossRef][ISI][Medline]
5. Garcia JL, Fernandez N, Garcia-Villalon AL, Monge L, Gomez B, and Dieguez G. Coronary vasoconstriction by endothelin-1 in anesthetized goats: role of endothelin receptors, nitric oxide and prostanoids. Eur J Pharmacol 315: 179–186, 1996.[CrossRef][ISI][Medline]
6. Garlichs CD, Zhang H, Mugge A, and Daniel WG. Beta-blockers reduce the release and synthesis of endothelin-1 in human endothelial cells. Eur J Clin Invest 29: 12–16, 1999.[ISI][Medline]
7. Heusch G, Baumgart D, Camici P, Chilian W, Gregorini L, Hess O, Indolfi C, and Rimoldi O. -Adrenergic coronary vasoconstriction and myocardial ischemia in humans. Circulation 101: 689–694, 2000.[Abstract/Free Full Text]
8. Heusch G and Deussen A. The effects of cardiac sympathetic nerve stimulation on perfusion of stenotic coronary arteries in the dog. Circ Res 53: 8–15, 1983.[Free Full Text]
9. Hurlimann D, Enseleit F, Noll G, Luscher TF, and Ruschitzka F. Endothelin antagonists and heart failure. Curr Hypertens Rep 4: 85–92, 2002.[ISI][Medline]
10. Kuo L, Davis MJ, and Chilian WM. Myogenic activity in isolated subepicardial and subendocardial coronary arterioles. Am J Physiol Heart Circ Physiol 255: H1558–H1562, 1988.[Abstract/Free Full Text]
11. Lavallee M, Takamura M, Parent R, and Thorin E. Crosstalk between endothelin and nitric oxide in the control of vascular tone. Heart Fail Rev 6: 265–276, 2001.[CrossRef][Medline]
12. Merkus D, Duncker DJ, and Chilian WM. Metabolic regulation of coronary vascular tone: role of endothelin-1. Am J Physiol Heart Circ Physiol 283: H1915–H1921, 2002.[Abstract/Free Full Text]
13. Mohrman DE and Feigl EO. Competition between sympathetic vasoconstriction and metabolic vasodilation in the canine coronary circulation. Circ Res 42: 79–86, 1978.[Free Full Text]
14. Muntz KH, Garcia C, and Hagler HK. ₁-Receptor localization in rat heart and kidney using autoradiography. Am J Physiol Heart Circ Physiol 249: H512–H519, 1985.[Abstract/Free Full Text]
15. Neri Serneri GG, Boddi M, Modesti PA, Cecioni I, Coppo M, Padeletti L, Michelucci A, Colella A, and Galanti G. Increased cardiac sympathetic activity and insulin-like growth factor-I formation are associated with physiological hypertrophy in athletes. Circ Res 89: 977–982, 2001.[Abstract/Free Full Text]
16. Piper HM, Volz A, and Schwartz P. Adult ventricular rat heart muscle cells. In: Cell Techniques in Heart and Vessel Research, edited by Piper HM. Heidelberg: Springer, 1990, p. 36–60.
17. Preisig-Muller R, Mederos y Schnitzler M, Derst C, and Daut J. Separation of cardiomyocytes and coronary endothelial cells for cell-specific RT-PCR. Am J Physiol Heart Circ Physiol 277: H413–H416, 1999.[Abstract/Free Full Text]
18. Shimizu K and McGrath BP. Sympathetic dysfunction in heart failure. Baillieres Clin Endocrinol Metab 7: 439–463, 1993.[CrossRef][ISI][Medline]
19. Stepp DW, Merkus D, Nishikawa Y, and Chilian WM. Nitric oxide limits coronary vasoconstriction by a shear stress-dependent mechanism. Am J Physiol Heart Circ Physiol 281: H796–H803, 2001.[Abstract/Free Full Text]
20. Tiefenbacher CP, DeFily DV, and Chilian WM. Requisite role of cardiac myocytes in coronary ₁-adrenergic constriction. Circulation 98: 9–12, 1998.[Abstract/Free Full Text]
21. Van Haperen R, Cheng C, Mees BM, van Deel E, de Waard M, van Damme LC, van Gent T, van Aken T, Krams R, Duncker DJ, and de Crom R. Functional expression of endothelial nitric oxide synthase fused to green fluorescent protein in transgenic mice. Am J Pathol 163: 1677–1686, 2003.[Abstract/Free Full Text]
22. Wang Y, Kanatsuka H, Akai K, Sugimura A, Kumagai T, Komaru T, Sato K, and Shirato K. Effects of low doses of endothelin-1 on basal vascular tone and autoregulatory vasodilation in canine coronary microcirculation in vivo. Jpn Circ J 63: 617–623, 1999.[CrossRef][Medline]
23. Winegrad S, Henrion D, Rappaport L, and Samuel JL. Self-protection by cardiac myocytes against hypoxia and hyperoxia. Circ Res 85: 690–698, 1999.[Abstract/Free Full Text]

This article has been cited by other articles:

				V. J. de Beer, O. Sorop, D. A. Pijnappels, D. H. Dekkers, F. Boomsma, J. M. J. Lamers, D. J. Duncker, and D. Merkus Integrative control of coronary resistance vessel tone by endothelin and angiotensin II is altered in swine with a recent myocardial infarction Am J Physiol Heart Circ Physiol, May 1, 2008; 294(5): H2069 - H2077. [Abstract] [Full Text] [PDF]

				J. D. Tune Withdrawal of vasoconstrictor influences in local metabolic coronary vasodilation Am J Physiol Heart Circ Physiol, November 1, 2006; 291(5): H2044 - H2046. [Full Text] [PDF]

				S. Pikkarainen, H. Tokola, R. Kerkela, M. Ilves, M. Makinen, H.-D. Orzechowski, M. Paul, O. Vuolteenaho, and H. Ruskoaho Inverse regulation of preproendothelin-1 and endothelin-converting enzyme-1beta genes in cardiac cells by mechanical load Am J Physiol Regulatory Integrative Comp Physiol, June 1, 2006; 290(6): R1639 - R1645. [Abstract] [Full Text] [PDF]

				X. Sun and D. D. Ku Selective right, but not left, coronary endothelial dysfunction precedes development of pulmonary hypertension and right heart hypertrophy in rats Am J Physiol Heart Circ Physiol, February 1, 2006; 290(2): H758 - H764. [Abstract] [Full Text] [PDF]

				J. Herrmann Peri-procedural myocardial injury: 2005 update Eur. Heart J., December 1, 2005; 26(23): 2493 - 2519. [Abstract] [Full Text] [PDF]

This Article Abstract Full Text (PDF) All Versions of this Article: 288/5/H2088    most recent 00522.2003v2 00522.2003v1 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 ISI Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via ISI Web of Science (6) Citing Articles via Google Scholar Google Scholar Articles by Merkus, D. Articles by Chilian, W. M. Search for Related Content PubMed PubMed Citation Articles by Merkus, D. Articles by Chilian, W. M.