Skip to content

Advertisement

  • Research article
  • Open Access
  • Open Peer Review

17β-estradiol effects on human coronaries and grafts employed in myocardial revascularization: a preliminary study

  • 1,
  • 1Email author,
  • 2,
  • 1,
  • 1,
  • 3,
  • 1,
  • 1,
  • 1 and
  • 1
Journal of Cardiothoracic Surgery20061:46

https://doi.org/10.1186/1749-8090-1-46

©  Polvani et al; licensee BioMed Central Ltd. 2006

  • Received: 10 November 2006
  • Accepted: 20 December 2006
  • Published:
Open Peer Review reports

Abstract

Background

This study was undertaken to compare the in vitro effects of 17β-estradiol on human epicardial coronary arteries, resistance coronary arteries and on arterial vessels usually employed as grafts in surgical myocardial revascularization.

Methods

Coronary artery rings (descending coronary artery, right coronary artery, circumflex coronary artery, first septal branch) and arterial graft rings (internal thoracic artery, gastro-epiploic artery) obtained from human heart donors with heart not suitable to cardiac transplantation were connected to force transducer for isometric force recording. Precontracted specimens with and without endothelium were exposed to increasing concentration of 17β-estradiol (3–30–300–3000 nmol/l) and to vehicle (0.1% v/v ethanol). We also evaluated the effects of 17β-estradiol on vessels before and 20 minutes after exposure to L-monomethyl-arginine and indomethacin.

Results

17β-estradiol induced a significant relaxation in all precontracted vessels (mean maximum effect: 78,6% ± 8,5). This effect was not different among the different rings and was not related to the presence of endothelium. N-monomethyl-L-arginine and indomethacin did not modify 17β-estradiol relaxant effect.

Conclusion

The vasodilator action of the 17β-estradiol is similar on coronary arteries, resistance coronary arteries and arterial vessels usually employed as grafts in myocardial revascularization.

Keywords

  • Coronary Artery Bypass Grafting
  • Resistance Vessel
  • Arterial Graft
  • Neointimal Proliferation
  • Vasorelaxant Effect

Background

The interest for 17β-estradiol as vasoactive and vasoprotective agent is raising, since it was observed that it takes effect directly on the vascular wall, improving vasodilatation and inhibiting neointimal proliferation [1–7]. New devices, such as 17β-estradiol-eluting- stents, were developed to protect revascularized heart [8], hypothesizing a new role of 17β-estradiol for tertiary prevention in coronary artery disease (CAD).

Coronary perfusion after coronary artery bypass grafting (CABG) is a complex system dependent on several factors, including gender and the type of grafts employed [9–14]. Women have smaller coronary arteries than men and it can lead to incomplete revascularization and increased risk of in-hospital mortality [10]. The type of graft employed can affect outcomes as arterial grafts permit superior long-term patency and lower mortality rate [11–14]. Moreover, blood flow distribution in cardiac wall is related to not only diastolic pressure and section area of epicardial vessels but also depends on the resistance to the blood flow determined by intramyocardial branches, i.e. first septal branch [15].

The effect of estrogen on coronary system after surgical myocardial revascularization should be evaluated considering together all vessels that permit blood circulation, including grafts, epicardial coronary arteries and resistance vessels. To date, a comprehensive evaluation of estrogenic action on coronary arteries system was not performed. This study was undertaken to compare the effect of 17β-estradiol on epicardial coronary arteries, resistance coronary vessels and arteries employed as grafts in CABG.

Methods

We evaluated the in vitro effect of 17β-estradiol on human epicardial coronary arteries (anterior interventricular artery, right coronary artery, circumflex artery) resistance vessels (first septal branch) and arteries usually employed in CABG (left internal mammary artery, gastroepiploic artery).

The vessels were obtained from 11 human donors whose heart was not suitable for cardiac transplantation and was harvested for banking cryopreserved valvular homografts. All patients were female (mean age 38 ± 11 years, range 18–54 years). All women had normal coronary arteries, without macroscopic atherosclerotic process.

Coronaries were dissected within 1 hours after the removal of heart and all segments were immediately put in a modified Krebs solution (composition in mmol/l: NaCl 118.3, KCl 4.7, CaCl2 2.5, MgSO4 1.2, KH2PO4 1.2, NaHCO3 25, EDTA Calcium 0.026, glucose 11.1, albumin 0.1) at 4°C to be conserved. At the time of experiment, at maximum 1 hour after dissection, the vessels were cut into 3–4 mm long rings and suspended in an organ bath containing 10 ml modified Krebs solution aerated constantly with 95% O2 and 5% CO2 and maintained at 37°C. Each ring was mounted on a triangular-shaped metal hook connected to force transducer for isometric force recordings. Resting force was 2 grams [16].

Each single experiment was conducted on two rings from the same vessel. In one ring endothelium was mechanically removed with a wooden applicator (Group 1) in order to simulate an atheromasic vessel. The ring was precontracted with prostaglandin F2α (PGF2α, 1 μmol/l), then histamine (0.1 μmol/l) was added and the absence of vasodilative effect confirmed the complete removal of the endothelium (Figure 1-A). In the other ring from the same vessel, endothelium was preserved (Group 2). It was precontracted with prostaglandin F2α (PGF2α, 1 μmol/l) and exposed to the same concentration of histamine (0.1 μmol/l) with subsequent complete vasodilatation (Figure 2-B).
Figure 1
Figure 1

A recording showing the relaxant effect of 17β-estradiol on human female coronary arteries. In panel A, histamine had no effects on a denuded ring. In panel B, endothelium was preserved and histamine had a relaxant effect. In panel C, a ring was precontracted with PGF2α and exposed to the solvent (ethanol), without vasorelaxation. Adding 3 μM of 17β-estradiol to the organ bath with ethanol, the force transducer recorded the maximum decrease in force within 10 minutes. Panel D shows the dose-dependent relaxation of a precontracted ring exposed to increasing concentrations of 17β-estradiol (3–30–300–3000 nmol/l).

Figure 2
Figure 2

The effects of 17β-estradiol on different vessels with and without endothelium. The effect of 17β-estradiol on vessels is expressed as the percentage relaxation of the maximum contraction induced by PGF2α. The relaxant effect of 17β-estradiol at each dose was similar in all groups (n = 22 for each group, p > 0.05 by repeated-measures analysis of variance). No intra-group significant difference was found between the same vessels with and without endothelium (data not shown). 17β-estradiol has a similar vasoactive effect on both epicardial coronaries and septal branch and arteries usually used as graft in myocardial revascularization at each concentration.

The rings (Group1 and Group2) were washed out and precontracted with prostaglandin F2α (PGF2α, 1 μmol/l). After the contraction plateau was reached (about 10 minutes), rings were exposed to the vehicle (0.1% v/v ethanol, Figure 1-C). The bath solution was replaced, the rings were precontracted again with prostaglandin F2α (PGF2α, 1 μmol/l) and, at the contraction plateau, they were exposed to increasing concentrations of 17β-estradiol (3–30–300–3000 nmol/l, Figure 1D).

At the end of the experiment, the rings were washed out and we evaluated the effects of increasing concentrations of 17β-estradiol after the exposition to L-monomethyl-arginine (L-NMMA, 0.1 mmol/l) and indomethacin (10 μmol/l), L-NMMA is a non-specific inhibitor of nitric oxide synthase (NOS) that permits to evaluate the role of nitric oxide (NO) in vasoactive action of estrogen. Indomethacin is a cyclo-oxygenase inhibitor that blocks endothelial synthesis of prostacyclin. The rings were pretreated with both L-NMMA and indomethacin together for 20 minutes and precontracted with prostaglandin F2α (PGF2α, 1 μmol/l). After the contraction plateau was reached (about 10 minutes), rings were exposed to increasing concentrations of 17β-estradiol (3–30–300–3000 nmol/l).

This study had the approval of our Institutional Ethics Committee.

Statistical analysis

The effect of 17β-estradiol on vessels was expressed as the percentage relaxation of the maximum contraction induced by PGF2α. Continuous variables were expressed as mean ± standard deviation of the mean (SD). Differences between two groups were evaluated using Student's t-test. Repeated-measures analysis of variance (ANOVA) was used to compare more than two means. If statistically significant, Student's paired t test was then performed, with Bonferroni's method used to correct for multiple comparisons. A p value of less than 0.05 was considered statistically significant. Statistical analyses were performed using SPSS 13.0 software (SPSS, Inc, Chicago, IL).

Results

17β-estradiol induced significant relaxation of precontracted coronary artery segments and vessels employed in CABG (compared with vehicle solvent, p < 0.05, data not shown). This vascular response to 17β-estradiol was concentration-dependent with a maximum effect at 3 μmol/l-dose (mean maximum effect: 78.6% ± 8.5%).

There were no significant differences in vasorelaxation between different types of vessels (p > 0.05, n = 22 in each group; Figure 2). It suggests that estrogen effect on vascular system is not dependent on vascular district and on segment's size.

The relaxant effect of estrogen was similar in groups with and without endothelium (p > 0.05, n = 66 in each group, Figure 3), suggesting an endothelium-independent mechanism of action. L-NMMA and indomethacin did not significantly inhibit the relaxation produced by increasing concentrations of 17β-estradiol (Figure 4), excluding a role of nitric oxide and prostacyclin on estrogen-dependent relaxation.
Figure 3
Figure 3

The effect of increasing concentrations (3–30–300–3000 nmol/l) of 17β-estradiol on vessels with and without endothelium. The relaxation is expressed as the percentage of the maximum effect obtained with PGF2α. The peak tension with PGF2α was 3.2 ± 1.3 for intact vessels and 3.4 ± 1.0 for denuded vessels. There were no significant differences in vascular response to estrogen in groups with or without endothelium at each estrogen concentration (n = 66 for group with endothelium, n = 66 for group without endothelium, p > 0.05).

Figure 4
Figure 4

The effect of L-NMMA (0.1 mmol/l) and indomethacin (10 μmol/l) on 17β-estradiol vasorelaxation. The relaxation is expressed as the percentage of the maximum effect obtained with PGF2α. The peak tension with PGF2α was 3.3 ± 0.9 for experiment before exposure to L-NMMA and indomethacin and 3.1 ± 1.2 for the experiments after exposure to L-NMMA and indomethacin. We did not find significant differences among groups at each 17β-estradiol concentration (n = 132 in each group, p > 0.05). No intra-group significant difference was found between different vessels and between vessels with and without endothelium (p > 0.05, data not shown).

Discussion

The relationship between 17β-estradiol and heart has been widely evaluated in the last decade, since it was observed that the risk of coronary artery disease significantly increases in women after menopause [17]. Several clinical studies focused on the protective role of postmenopausal HRT with contrasting results that leave the debate opened [18, 19]. We shifted the attention on tertiary prevention of CAD to understand the vasoactive effects of 17β-estradiol on all conduits of the revascularized heart.

Our main question regarded the eventual diverse effects of estrogen on resistance vessel, epicardial vessels and arteries commonly employed as graft in CABG. Several studies evaluated only epicardial vessels [16, 20–23], without considering the importance of resistance vessels on heart perfusion. Moreover, LIMA graft was found responsible to estrogen but no comparison with coronaries was performed [24]. This study demonstrated a global acute vasorelaxant response of all vessels to 17β-estradiol which ameliorates all the complex physiology of blood flow in heart and arterial grafts. Hence, estrogen can acutely increase myocardial perfusion in women after coronary artery bypass grafting, acting through both a vasodilatation of coronary epicardial vessels and grafts and a decrease in resistance offered by resistance vessels.

The estrogenic vasoactive effect was found similar on normal and endothelium-deprived segments, confirming previous data on epicardial vessels [16, 22, 23]. Impaired-endothelium is characteristic of atherosclerotic coronaries and diseased arterial grafts. Surgical maneuvers are demonstrated to impair graft's endothelium and coronaries at incision site, worsening the endothelial function and leading to the well-known graft disease. The endothelium-independent vasorelaxation can be helpful in preventing perioperative vasoconstriction due to impaired endothelium and arterial graft spasm [23, 24]. Moreover, estrogens accelerate endothelial cells growth, increasing local expression of vascular endothelial growth factors and inhibiting endothelial cells apoptosis [25]. This estrogen-related rapid reendothelialization, as well as vasorelaxation and inhibition of neointimal proliferation, led to the development of new estrogen-eluting stents [8] and can also represent protective effects for surgical revascularized heart. It could be useful especially in female sex, in which perioperative and postoperative complications are increased by an unfavorable anatomy [9, 10].

The vasorelaxant mechanisms of 17β-estradiol on vascular conduits are far to be completely clarified [26]. New data about non-genomic mechanisms of action lead to consider 17β-estradiol also as an acute and mid-term vasodilator. 17β-estradiol both stimulates endothelial NO production in a non-genomic manner and has vasorelaxant effects on impaired vessels acting on the muscular layer through an endothelium-independent mechanism. Smooth muscular cells respond to estrogens stimulating myocyte NO-synthesis or through similar Ca-antagonist mechanisms [16, 23, 27, 28]. Our study confirms the similar Ca-antagonist mechanism, as L-NMMA (N-monomethyl-L-arginine) does not change vascular response, even if we did not evaluate the myocyte NO-synthesis.

Limitations of the study

This study was performed on in vitro specimens and the concomitant in vivo effects could not be evaluated. By its nature, it did not considered chronic estrogenic effects that can be related to different mechanisms, such as genomic induction. Moreover, we focused the attention on endothelium-independent mechanisms similar to Ca-antagonist, as they are responsible of vasodilatation on both normal and impaired vessels, which are characteristic of revascularized heart.

Conclusion

This study demonstrated that 17β-estradiol has a similar relaxant effect on human female coronary arteries (epicardial capacitance arteries and resistance vessels) and arteries used as graft in CABG. Acute estrogenic administration can have vasorelaxant effect on all female revascularized heart, thus protecting coronaries and grafts and favoring reendothelialization.

List of abbreviations

ANOVA: 

analysis of variance

CABG: 

coronary artery bypass grafting

CAD: 

coronary artery disease

HRT: 

hormone replacement therapy

L-NMMA: 

L-monomethyl-arginine

LIMA: 

left internal mammary artery

NO: 

nitric oxide

NOS: 

nitric oxide synthase

PGF2α : 

prostaglandin F2α

SD: 

standard deviation of the mean

Declarations

Authors’ Affiliations

(1)
Department of Cardiovascular Surgery, University of Milan, Centro Cardiologico Monzino, Via Parea 4, 20138 Milan, Italy
(2)
Department of Pharmacological Sciences, University of Milan, Via Balzaretti 9, 20133 Milan, Italy
(3)
Division of Cardiothoracic Surgery, College of Physicians and Surgeon of Columbia University – New York Presbyterian Hospital, Columbia University Medical Center, Milstein Hospital Building, 7GN-435 177 Fort Washington Avenue, New York, NY 10032, USA

References

  1. Matsubara Y, Murata M, Kawano K, Zama T, Aoki N, Yoshino H, Watanabe G, Ishikawa K, Ikeda Y: Genotype distribution of estrogen receptor polymorphism in men and postmenopausal women from healthy and coronary populations and its relation to serum lipid levels. Arterioscler Thromb Vasc Biol. 1997, 17 (11): 3006-3012.View ArticlePubMedGoogle Scholar
  2. Venkov CD, Rankin AB, Vaughan DE: Identification of authentic estrogen receptor in cultured endothelial cells. A potential mechanism for steroid hormone regulation of endothelial function. Circulation. 1996, 94 (4): 727-733.View ArticlePubMedGoogle Scholar
  3. Karas RH, Patterson BL, Mendelsohn ME: Human vascular smooth muscle cells contain functional estrogen receptor. Circulation. 1994, 89 (5): 1943-1950.View ArticlePubMedGoogle Scholar
  4. Lin AL, Gonzales R, Carey KD, Shain SA: Estradiol-17β affects estrogen receptor distribution and elevates progesterone receptor content in baboon aorta. Arteriosclerosis. 1986, 6: 495-504.View ArticlePubMedGoogle Scholar
  5. Krasinski K, Spyridopoulos I, Asahara T, Van Der Zee R, Isner JM, Losordo DW: Estradiol accelerates functional endothelial recovery after arterial injury. Circulation. 1997, 95: 1768-1772.View ArticlePubMedGoogle Scholar
  6. Chandrasekar B, Tanguay JF: Local delivery of 17-beta-estradiol decreases neointimal hyperplasia after coronary angioplasty in a porcine model. J Am Coll Cardiol. 2000, 36 (6): 1972-8. 10.1016/S0735-1097(00)00940-2.View ArticlePubMedGoogle Scholar
  7. Chandrasekar B, Nattel S, Tanguay JF: Coronary artery endothelial protection after local delivery of 17beta-estradiol during balloon angioplasty in a porcine model: a potential new pharmacologic approach to improve endothelial function. J Am Coll Cardiol. 2001, 38 (5): 1570-6. 10.1016/S0735-1097(01)01552-2.View ArticlePubMedGoogle Scholar
  8. Abizaid A, Albertal M, Costa MA, Abizaid AS, Staico R, Feres F, Mattos LA, Sousa AG, Moses J, Kipshidize N, Roubin GS, Mehran R, New G, Leon MB, Sousa JE: First human experience with the 17-beta-estradiol-eluting stent: the Estrogen And Stents To Eliminate Restenosis (EASTER) trial. J Am Coll Cardiol. 2004, 43 (6): 1118-21. 10.1016/j.jacc.2004.01.023.View ArticlePubMedGoogle Scholar
  9. Corbineau H, Lebreton H, Langanay T, Logeais Y, Leguerrier A: Prospective evaluation of coronary arteries: influence on operative risk in coronary artery surgery. Eur J Cardiothorac Surg. 1999, 16 (4): 429-434. 10.1016/S1010-7940(99)00295-X.View ArticlePubMedGoogle Scholar
  10. O'Connor NJ, Morton JR, Birkmeyer JD, Olmstead EM, O'Connor GT: Effect of coronary artery diameter in patients undergoing coronary bypass surgery. Circulation. 1996, 93 (4): 652-655.View ArticlePubMedGoogle Scholar
  11. Motwani JG, Topol EJ: Aortocoronary saphenous vein graft disease: pathogenesis, predisposition, and prevention. Circulation. 1998, 97 (9): 916-931.View ArticlePubMedGoogle Scholar
  12. He GW: Arterial grafts for coronary surgery: vasospasm and patency rate. J Thorac Cardiovasc Surg. 2001, 121 (3): 431-433. 10.1067/mtc.2001.113593.View ArticlePubMedGoogle Scholar
  13. Boylan MJ, Lytle BW, Loop FD, Taylor PC, Borsh JA, Goormastic M, Cosgrove DM: Surgical treatment of isolated left anterior descending coronary stenosis. Comparison of left internal mammary artery and venous autograft at 18 to 20 years of follow up. J Thorac Cardiovasc Surg. 1994, 107 (3): 657-662.PubMedGoogle Scholar
  14. Loop FD, Lytle BW, Cosgrove DM, Stewart RW, Goormastic M, Williams GW, Golding LA, Gill CC, Taylor PC, Sheldon WC: Influence of the internal-mammary-artery graft on 10-years survival and other cardiac events. N Engl J Med. 1986, 314 (1): 1-6.View ArticlePubMedGoogle Scholar
  15. Chilian WM, Eastham CL, Layne SM, Marcus ML: Small vessel phenomena in the coronary microcirculation: phasic intramyocardial perfusion and coronary microvascular dynamics. Progr Cardiovasc Dis. 1988, 31 (1): 17-38. 10.1016/0033-0620(88)90009-6.View ArticleGoogle Scholar
  16. Mugge A, Riedel M, Barton M, Kuhn M, Lichtlen PR: Endothelium independent relaxation of human coronary arteries by 17β-oestradiol in vitro. Cardiovasc Res. 1993, 27 (11): 1939-1942.View ArticlePubMedGoogle Scholar
  17. Mendelsohn ME, Karas RH: The protective effect of estrogen on the cardiovascular system. N Engl J Med. 1999, 340 (23): 1801-1811. 10.1056/NEJM199906103402306.View ArticlePubMedGoogle Scholar
  18. Sullivan JM, El-Zeky F, Vander Zwaag R, Ramanathan KB: Effect on survival of estrogen replacement therapy after coronary artery bypass grafting. Am J Cardiol. 1997, 79 (7): 847-850. 10.1016/S0002-9149(97)00001-5.View ArticlePubMedGoogle Scholar
  19. Paoletti R, Wenger NK: Review of the international position paper on women's health and menopause. A comprehensive approach. Circulation. 2003, 107: 1336-1339. 10.1161/01.CIR.0000054674.89019.1A.View ArticlePubMedGoogle Scholar
  20. Jiang CW, Sarrel PM, Lindsay DC, Poole-Wilson PA, Collins P: Endothelium-independent relaxation of rabbit coronary artery by 17β-estradiol in vitro. Br J Pharmacol. 1991, 104 (4): 1033-1037.View ArticlePubMedPubMed CentralGoogle Scholar
  21. Williams JK, Adams MR, Klopfenstein HS: Estrogen modulates responses of atherosclerotic coronary arteries. Circulation. 1990, 81 (5): 1680-1687.View ArticlePubMedGoogle Scholar
  22. Reis SE, Gloth ST, Blumenthal RS, Resar JR, Zacur HA, Gerstenblith G, Brinker JA: Ethinyl estradiol acutely attenuates abnormal coronary vasomotor responses to acetylcholine in postmenopausal women. Circulation. 1994, 89 (1): 52-60.View ArticlePubMedGoogle Scholar
  23. Chester AH, Jiang C, Borland JA, Yacoub MH, Collins P: Oestrogen relaxes human pericardial coronary arteries through non-endothelium-dependent mechanism. Coron Artery Dis. 1995, 6 (5): 417-422. 10.1097/00019501-199505000-00009.View ArticlePubMedGoogle Scholar
  24. Polvani G, Marino MR, Roberto M, Dainese L, Parolari A, Pompilio G, Di Matteo S, Fumero A, Cannata A, Barili F, Biglioli P: Acute effects of 17β-estradiol on left internal mammary graft after coronary artery bypass surgery. Ann Thorac Surg. 2002, 74: 695-699. 10.1016/S0003-4975(02)03742-6.View ArticlePubMedGoogle Scholar
  25. Chandrasekar B, Sirois MG, Geoffroy P, Lauzier D, Nattel S, Tanguay JF: Local delivery of 17beta-estradiol improves reendothelialization and decreases inflammation after coronary stenting in a porcine model. Thromb Haemost. 2005, 94 (5): 1042-7.PubMedGoogle Scholar
  26. Mendelsohn ME: Genomic and nongenomic effects of estrogen in vasculature. Am J Cardiol. 2002, 90 (1A): 3F-6F. 10.1016/S0002-9149(02)02418-9.View ArticlePubMedGoogle Scholar
  27. White RE, Han G, Maunz M, Dimitropoulou C, El-Mowafy AM, Barlow RS, Catravas JD, Snead C, Carrier GO, Zhu S, Yu X: Endothelium-independent effect of estrogen on Ca2+-activated K+ channels in human coronary artery smooth muscle cells. Cardiovasc Res. 2002, 53 (3): 650-661. 10.1016/S0008-6363(01)00428-X.View ArticlePubMedGoogle Scholar
  28. White RE, Darkow DJ, Lang JL: Estrogen relaxes coronary arteries by opening BKCa channels through a cGMP-dependent mechanism. Circ Res. 1995, 77: 936-942.View ArticlePubMedGoogle Scholar

Copyright

© Polvani et al; licensee BioMed Central Ltd. 2006

This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Advertisement

Journal of Cardiothoracic Surgery

ISSN: 1749-8090

Contact us