Review

The Cardiopulmonary Effects of the Calcitonin Gene-related Peptide Family

10.4274/tjps.galenos.2019.47123

  • Gökçen TELLİ
  • Banu Cahide TEL
  • Bülent GÜMÜŞEL

Received Date: 12.06.2019 Accepted Date: 27.06.2019 Turk J Pharm Sci 2020;17(3):349-356

Cardiopulmonary diseases are very common among the population. They are high-cost diseases and there are still no definitive treatments. The roles of members of the calcitonin-gene related-peptide (CGRP) family in treating cardiopulmonary diseases have been studied for many years and promising results obtained. Especially in recent years, two important members of the family, adrenomedullin and adrenomedullin2/intermedin, have been considered new treatment targets in cardiopulmonary diseases. In this review, the roles of CGRP family members in cardiopulmonary diseases are investigated based on the studies performed to date.

Keywords: CGRP family, cardiopulmonary diseases, adrenomedullin, adrenomedullin2/intermedin, pulmonary hypertension

INTRODUCTION

The calcitonin gene-related peptide (CGRP) family consists of calcitonin, amylin (AMY), CGRP, adrenomedullin (ADM), calcitonin receptor (CTR) stimulating peptides 1-3, and the latest member of the family, ADM2/intermedin (IMD).1,2 These peptides are included in the same family because of their similar chemical structures and they have important roles in the homeostasis of the body.3,4,5,6 The effects of these peptides on the cardiovascular and pulmonary systems, especially ADM and ADM2/IMD, sparked interest as many studies were presented for the new targets of cardiovascular diseases.7,8,9 In this review, we aim to summarize the cardiopulmonary effects of the CGRP family.


DISTRIBUTION OF MEMBERS OF THE CGRP FAMILY

Peptides of the CGRP family are widely expressed in the body. The first peptide of this family, calcitonin, was synthesized by a calcium-dependent mechanism and released from thyroid C-cells.10,11 Another peptide, AMY, was isolated from amyloid plaques in β-cells found in pancreatic islets of Langerhans.12 The rest of the family, CGRP, ADM, and ADM2/IMD, have more effect on the cardiovascular and pulmonary system. CGRP is expressed in both central and peripheral nerves associated with blood vessels. Perivascular nerves were suggested as important sources of plasma CGRP. Although CGRP is mainly expressed in nerves, it is also located in endothelial cells, adipocytes, keratinocytes, and immune cells.13

ADM was isolated for the first time from human pheochromocytoma cells; however, in following years it has been shown to be expressed in many tissues in the body.14 It is found in the adrenal medulla, kidneys, lungs, ventricles, and especially endothelial cells in high amounts.15,16

The distribution of ADM2/IMD is largely similar to that of ADM. The expression of ADM2/IMD was demonstrated in the brain, liver, intestines, heart, kidneys, plasma, hypothalamus, and like ADM widely in endothelial cells.17,18,19,20,21,22 In addition to being expressed widely in physiological conditions, their levels change under pathological conditions.13,23,24,25,26


RECEPTORS OF THE CGRP FAMILY

The peptides of the CGRP family interact with CTRs or calcitonin receptor-like receptors (CLRs). CTRs were first identified in pigs in 1991 and two different variants were found in humans, named hCTaR and hCTbR. These receptors are located on the cell surface. hCTaR is widely distributed in the body, while hCTbR was found in the placenta, ovaries, lungs, and bone marrow.27 CLRs were first demonstrated in rats in 1993 and 2 years later were shown in different tissues of humans.28,29 CLRs were found in the central nervous system, kidneys and spleen, endothelial cells, vascular smooth muscle cells, and the heart. CTRs and CLRs are G protein-dependent receptors and contain 7 transmembrane regions.30,31 The receptors must also interact with the related receptor-activating modified protein (RAMP), depending on the type of peptide. These proteins facilitate the transfer of receptors from the plasma membrane and translocations of them into the cells.32,33 RAMPs are composed of 148 to 189 amino acids and although they exhibit a homology less than 30%, they are structurally similar to each other. These proteins are named RAMP1, RAMP2, and RAMP3.13 AMY shows high affinity when CTRs are activated by RAMPs.33,34 RAMPs that bind to CTRs allow the receptor to show affinity to AMY instead of calcitonin. When the CTRs are connected with RAMP1, RAMP2, and RAMP3 they are called AMY1, AMY2, and AMY3, respectively. CGRP and ADM are activated by binding to CLRs. CLRs must interact with RAMP1 in order to function as CGRP receptors. CLRs must be bound to RAMP2 and -3 to act as ADM receptors (AM1 and AM2, respectively) (Table 1).

RAMP1 is commonly found in the uterus, bladder, brain, pancreas, and gastrointestinal tract.35,36,37 It has been also shown in the veins, perivascular nerves, arteries, and endothelial cells of arterioles and smooth muscle cells and cardiomyocytes.38 RAMP2 is found in the lungs, spleen, immune system, and kidneys, and widely distributed in the cardiovascular system, especially in vascular endothelium and smooth muscle cells.39 RAMP3 is found in high levels in the kidneys, lungs, and spleen, similar to RAMP2.35,36

Other than RAMPs, CLRs need another adapter protein to show optimum activity. This protein is called receptor component protein (RCP) and provides more effective binding with stimulator G protein and thus increases the activity of peptides32,40 (Figure 1).


CARDIOPULMONARY EFFECTS OF THE CGRP FAMILY

Peptides of the CGRP family show widespread biological activity in the body, and in the cardiopulmonary system especially CGRP, ADM, and ADM2/IMD have remarkable effects.


Amylin

AMY acts on the cardiovascular system via CGRP receptors.41 However, AMY has to reach a high plasma concentration to show activity. Intravenous (i.v.) AMY application provided potent vasodilatation and decreased arterial blood pressure in rats.42 However, human studies showed no significant effect after AMY application.43 In studies on rat cardiomyocytes and isolated heart, AMY showed a direct inotropic effect that was mediated by CGRP receptors. However, because of the side effects on the heart of high doses of AMY, it was stated that it could not be applied clinically.44,45


Calcitonin gene-related peptide

CGRP is one of the most potent and effective vasodilators and it has a longer duration of action.46,47 Its relaxing effects on coronary, cerebral, pulmonary, and renal arteries were shown in both in vitro and in vivo experiments. CGRP has also regulatory effects on the vascular system; it was shown to reduce the vascular resistance and to increase the blood supply to organs in both normotensive and hypertensive animals.48,49 In hypertensive rats, systemically administrated CGRP decreased blood pressure and had positive inotropic and chronotropic effects. After ischemic injury CGRP released in rats and also CGRP infusion reduced ischemia-reperfusion-induced arrhythmias. In addition, many studies have shown that CGRP is also protective against ischemic damage. These effects of CGRP are generally thought to be the result of its vasodilatory effect.50,51,52 Furthermore, CGRP also suppressed the release of potent vasoconstrictor agents such as endothelin and angiotensin.53

CGRP provided important relaxation in the pulmonary vascular system and was found in high amounts in lung tissue.54 In pulmonary hypertension (PH), plasma CGRP levels were decreased and CGRP infusion has been shown to be effective in treatment.13,23,24,25 Adenovirus-mediated CGRP transfection before chronic hypoxia exposure in mice lungs provided cyclic adenosine monophosphate (cAMP)-mediated protection against pulmonary vascular resistance and decreased vascular remodeling.53 CGRP has been shown to provide protection against hypoxia-induced remodeling in human tissue studies55 and it was shown that in rat hypoxic lung the expression levels of the CGRP receptor adapter protein RAMP1 were increased.26

CGRP shows all these effects through CGRP receptor and the effects of CGRP on the cardiovascular system are inhibited in the presence of selective CGRP antagonist CGRP8-37.46,56,57,58 It is suggested that both endothelium-dependent and endothelium-independent mechanisms have roles in CGRP-mediated vasodilatation.5,59,60 In many tissues, such as cat cerebral artery, rat mesenteric artery, and pig coronary artery, the increase in cAMP was measured after CGRP administration and in the endothelium-damaged vessels vasodilation was also observed. However, even high doses of CGRP did not stimulate the cyclic guanosine monophosphate (cGMP) levels directly.59,60 Therefore, it may indicate that CGRP directly activates cAMP-dependent vasodilation.61,62,63 In the studies that were performed in the pig coronary artery and guinea pig ureter, CGRP-mediated vasodilation was inhibited by the KATP channel inhibitor glibenclamide. Therefore, it was stated that the increase in cAMP activates protein kinase A and subsequently KATP channels.61,63,64,65,66,67 Basal and nitric oxide (NO)-stimulated CGRP release were increased in the human right atrium in patients that underwent cardiopulmonary bypass.68,69 However, there are also contradictory studies that indicated the role of endothelium in CGRP-mediated vasodilation. CGRP provided NO- and cGMP-dependent vasodilation in the rat aorta.70

On the other hand, in the perivascular nerves of the rat mesentery artery, CGRP was found more sensitive to endothelin-1 mediated constructions and this effect was not associated with NO or cyclic nucleotides.71


Adrenomedullin

For many years, the effects of ADM on the cardiovascular system have attracted attention. Potent, NO-mediated hypotension was observed after the infusion of ADM both in animals and in humans.72,73,74 After acute and chronic administration of ADM in rats, total peripheral vascular resistance and blood pressure were decreased significantly. The heart rate and cardiac output were increased simultaneously. Similar effects were also observed in hypertensive rats.75,76 ADM is an important vasorelaxant agent, especially in the mesentery, renal, pulmonary, and cerebral arteries and aorta, but the mechanism of this effect varies according to species and the vascular bed.77,78,79,80 The vasorelaxing effects act through CGRP and ADM receptors. In the rat mesenteric artery and dog renal arteries, the relaxing effect of ADM was inhibited in the presence of CGRP receptor antagonist, whereas in some studies that were performed in the cerebral arteries of cat and rat hind limb, inhibition of CGRP receptors did not alter the relaxation response.78,81,82 Similarly, the role of endothelium and NO in the relaxation effect of ADM also varies between different studies. Numerous studies have shown that endothelium-mediated vasorelaxation occurred in different vessels such as the rat renal, pulmonary, and mesenteric arteries and vasorelaxation was inhibited in the presence of NO synthase (NOS) inhibitors.72,83,84 However, in contrast to these studies, no changes were observed in the presence of NOS inhibitor in studies that were performed in isolated rat lung, cat hind limb arteries, and the cat penile artery.85,86,87 Studies in human and dog coronary arteries and rat cerebral arteries showed inhibited ADM response with high potassium.78,88,89 Although there are contradictory results in the literature, it has been shown in many studies that ADM provides relaxation through the cAMP, NO, or K+ channels in vascular systems.90

According to its potent and long-lasting vasodilatory activity in the peripheral microcirculation, ADM also could be effective in PH.91 In hypoxia-induced PH, ADM reduced pulmonary arterial pressure.92 Systemic i.v. administration of ADM reduced pulmonary vascular resistance and increased arterial oxygen levels with no effect on systemic blood pressure.93 In the studies performed in PH patients, the plasma level of ADM increased along with the severity of the disease. In contrast to the increase in the endogenous production of ADM, i.v. ADM administration reduced pulmonary artery pressure and pulmonary vascular resistance in PH patients.94,95 In another study performed with a small number of PH patients, acute inhaled ADM was shown to improve selectively the hemodynamic parameters in the pulmonary system and increase exercise capacity.96 Multicenter, randomized, controlled clinical trials should be conducted to evaluate the long-term safety and efficacy of ADM, to be able to consider it as a future treatment target in PH.9


Adrenomedullin2/intermedin

ADM2/IMD has quite a similar structure and function to CGRP and ADM. Therefore, it is also expected that ADM2/IMD can be effective in the vascular system. In many studies, blood pressure and vascular resistance were decreased and the heart rate was increased with the application of ADM2/IMD.17,30,97,98 After cardiac ischemia/reperfusion injury, the administration of ADM2/IMD increased the coronary perfusion and contractile strength of the left ventricle and reduced myocardial infarct size, hypertrophy, and cardiac fibrosis.99,100,101 In normotensive and hypertensive rats, i.v. infusion of ADM2/IMD increased cardiac output by reducing total peripheral vascular resistance.102 ADM2/IMD has been shown to be a potent vasodilator in many vessel beds such as pulmonary, renal, and abdominal arteries.103,104,105,106

CGRP8-37 and ADM receptor antagonist AM22-52 inhibited the effects of ADM2/IMD on the cardiovascular system under both physiological and pathophysiological conditions. The CLR/RAMP receptors are responsible for the actions of ADM2/IMD in the cardiovascular system.17,20,103 Although the effects of ADM2/IMD on the cardiovascular system frequently act through the CGRP receptors, in different vascular beds ADM2/IMD can interact with the both CGRP and ADM receptors.5,57 The ADM2/IMD-mediated response acts through CGRP receptor in the hypotension of rat systemic pressure and the vasodilation of rat coronary, carotid, supramesenteric, and pulmonary arteries. However, the ADM2/IMD responses were AM1 and AM2 receptor-mediated in pig coronary and rat renal arteries.17,20,103,105,107,108 Several studies have shown that the cardiovascular effects of ADM2/IMD are endothelium-mediated and NO-dependent. In the pulmonary vascular system and aorta, the relaxation responses were inhibited by the presence of NOS inhibitor Nω-Nitro-L-arginine methyl ester hydrochloride and in the damaged endothelium.99,103,109 The NO production increased dose-dependently with ADM2/IMD administration in cerebral endothelial cells and pulmonary smooth muscle cells.110,111

The positive inotropic effects of ADM2/IMD and the role in cell proliferation, apoptosis, and cell migration were related to the increase in cAMP production.112,113,114 The mRNA and protein levels of ADM2/IMD increased in the right ventricles, lung tissues, and plasma of hypoxia-induced pulmonary hypertensive rats.115,116,117 The symptoms of PH were alleviated by ADM2/IMD treatment in rats, right ventricular hypertrophy was prevented, and hypoxic pulmonary vascular remodeling was inhibited.111 According to studies that were performed in pulmonary hypertensive rats, ADM2/IMD is thought to be effective in PH.118 In chronic hypoxia-induced PH ADM2/IMD provided potent vasodilation in the pulmonary arteries of rats and intraarterial administration reduced the perfusion pressure of hypoxic lungs. This reduction indicates the possible application of ADM2/IMD administration in humans with PH.119,120


CONCLUSION

Peptides of the CGRP family exhibit cardiopulmonary effects and have been investigated for many years. Especially CGRP and ADM were proposed as new vasodilator agents in the treatment of many cardiovascular disease, such as hypertension and PH. ADM2/IMD is also a potent vasodilator in the cardiopulmonary system and in recent years it has been shown as a new drug candidate for cardiometabolic disease. However, further investigations should be performed for understanding these possible effects of ADM2/IMD before clinical investigations.


Conflicts of interest: No conflict of interest was declared by the authors. The authors alone are responsible for the content and writing of this article.

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  1. Born W, Fischer JA. The Calcitonin Peptide Family: What Can We Learn from Receptor Knock Out  and Transgenic Mice. In: Hay DL, Dickerson IM, eds. The Calcitonin Gene-related Peptide Family Form, Function and Future Perspectives. Springer Dordrecht Heidelberg London New York; Springer; 2010:75-86.
  2. Ghatta S, Ramarao P. Increased contractile responses to 5-Hydroxytryptamine and Angiotensin II in high fat diet fed rat thoracic aorta. Lipids Health Dis. 2004;3:19.
  3. Wimalawansa SJ. Amylin, calcitonin gene-related peptide, calcitonin, and adrenomedullin: a peptide superfamily. Crit Rev Neurobiol. 1997;11:167-239.
  4. Muff R, Born W, Fischer JA. Adrenomedullin and related peptides: receptors and accessory proteins. Peptides. 2001;22:1765-1772.
  5. Brain SD, Grant AD. Vascular actions of calcitonin gene-related peptide and adrenomedullin. Physiol Rev. 2004;84:903-934.
  6. Ren YS, Yang JH, Zhang J, Pan CS, Yang J, Zhao J, Pang YZ, Tang CS, Qi YF. Intermedin 1-53 in central nervous system elevates arterial blood pressure in rats. Peptides. 2006;27:74-79.
  7. Zhang SY, Xu MJ, Wang X. Adrenomedullin 2/intermedin: a putative drug candidate for treatment of cardiometabolic diseases. Br J Pharmacol. 2018;175:1230-1240.
  8. Nagaya N, Kangawa K. Adrenomedullin in the treatment of pulmonary hypertension. Peptides. 2004;25:2013-2018.
  9. Raja SG, Raja SM. Treating pulmonary arterial hypertension: current treatments and future prospects. Ther Adv Chronic Dis. 2011;2:359-370.
  10. Copp DH. Calcitonin: discovery, development, and clinical application. Clin Invest Med. 1994;17:268-277.
  11. Copp DH, Cameron EC. Demonstration of a hypocalcemic factor (calcitonin) in commercial parathyroid extract. Science. 1961;134:2038.
  12. Westermark P, Wernstedt C, Wilander E, Sletten K. A novel peptide in the calcitonin gene related peptide family as an amyloid fibril protein in the endocrine pancreas. Biochem Biophys Res Commun. 1986;140:827-831.
  13. Russell FA, King R, Smillie SJ, Kodji X, Brain SD. Calcitonin gene-related peptide: physiology and pathophysiology. Physiol Rev. 2014;94:1099-1142.
  14. Kitamura K, Sakata J, Kangawa K, Kojima M, Matsuo H, Eto T. Cloning and characterization of cDNA encoding a precursor for human adrenomedullin. Biochem Biophys Res Commun. 1993;194:720-725.
  15. Sugo S, Minamino N, Shoji H, Kangawa K, Kitamura K, Eto T, Matsuo H. Production and secretion of adrenomedullin from vascular smooth muscle cells: augmented production by tumor necrosis factor-alpha. Biochem Biophys Res Commun. 1994;203:719-726.
  16. Sugo S, Minamino N, Kangawa K, Miyamoto K, Kitamura K, Sakata J, Eto T, Matsuo H. Endothelial cells actively synthesize and secrete adrenomedullin. Biochem Biophys Res Commun. 1994;201:1160-1166.
  17. Roh J, Chang CL, Bhalla A, Klein C, Hsu SY. Intermedin is a calcitonin/calcitonin gene-related peptide family peptide acting through the calcitonin receptor-like receptor/receptor activity-modifying protein receptor complexes. J Biol Chem. 2004;279:7264-7274.
  18. Takei Y, Inoue K, Ogoshi M, Kawahara T, Bannai H, Miyano S. Identification of novel adrenomedullin in mammals: a potent cardiovascular and renal regulator. FEBS Lett. 2004;556:53-58.
  19. Taylor MM, Bagley SL, Samson WK. Intermedin/adrenomedullin-2 acts within central nervous system to elevate blood pressure and inhibit food and water intake. Am J Physiol Regul Integr Comp Physiol. 2005;288:919-927.
  20. Kobayashi Y, Liu YJ, Gonda T, Takei Y. Coronary vasodilatory response to a novel peptide, adrenomedullin 2. Clin Exp Pharmacol Physiol. 2004;31(Suppl 2):49-50.
  21. Takei Y, Hyodo S, Katafuchi T, Minamino N. Novel fish-derived adrenomedullin in mammals: structure and possible function. Peptides. 2004;25:1643-1656.
  22. Takahashi K, Kikuchi K, Maruyama Y, Urabe T, Nakajima K, Sasano H, Imai Y, Murakami O,  Totsune K. Immunocytochemical localization of adrenomedullin 2/intermedin-like immunoreactivity in human hypothalamus, heart and kidney. Peptides. 2006;27:1383-1389.
  23. Keith IM, Ekman R. Dynamic aspects of regulatory lung peptides in chronic hypoxic pulmonary hypertension. Exp Lung Res. 1992;18:205-224.
  24. Keith IM, Looi  STA, Kraiczi H, Ekman R. Three-week neonatal hypoxia reduces blood CGRP and causes persistent pulmonary hypertension in rats. Am J Physiol Heart Circ Physiol. 2000;279:1571-1578.
  25. Looi STA, Ekman R, Lippton H, Cary J, Keith I. CGRP and somatostatin modulate chronic hypoxic pulmonary hypertension. Am J Phsiol. 1992;263:681-690.
  26. Qing X, Svaren J, Keith IM. mRNA expression of novel CGRP1 receptors and their activity-modifying proteins in hypoxic rat lung. Am J Physiol Lung Cell Mol Physiol, 2001;280:547-554.
  27. Kuestner RE, Elrod RD, Grant FJ, Hagen FS, Kuijper JL, Matthewes SL, O’Hara PJ, Sheppard PO, Stroop SD, Thompson DL. Cloning and characterization of an abundant subtype of the human calcitonin receptor. Mol Pharmacol. 1994;46:246-255.
  28. Flühmann B, Muff R, Hunziker W, Fischer JA, Born W. A human orphan calcitonin receptor-like structure. Biochem Biophys Res Commun. 1995;206:341-347.
  29. Njuki F, Nicholl CG, Howard A, Mak JC, Barnes PJ, Girgis SI, Legon S. A new calcitonin-receptor-like sequence in rat pulmonary blood vessels. Clin Sci (Lond). 1993;85:385-388.
  30. Pan CS, Yang JH, Cai DY, Zhao J, Gerns H, Yang J, Chang JK, Tang CS, Qi YF. Cardiovascular effects of newly discovered peptide intermedin/adrenomedullin 2. Peptides 2005;26:1640-1646.
  31. Park K-Y, Russo AF. Genetic Regulation of CGRP and Its Actions. In: Hay DL, Dickerson IM, eds. The Calcitonin Gene-related Peptide Family Form, Function and Future Perspectives. Springer Dordrecht Heidelberg London New York; Springer; 2010:97-114.
  32. Juaneda C, Dumont Y, Quirion R. The molecular pharmacology of CGRP and related peptide receptor subtypes. Trends Pharmacol Sci. 2000;21:432-438.
  33. McLatchie LM, Fraser NJ, Main MJ, Wise A, Brown J, Thomson N, Solari R, Lee MG, Foord SM. RAMPs regulate the transport and ligand specificity of the calcitonin-receptor-like receptor. Nature. 1998;393:333-339.
  34. Muff R, Bühlmann N, Fischer JA, Born W. An amylin receptor is revealed following co-transfection of a calcitonin receptor with receptor activity modifying proteins-1 or -3. Endocrinology. 1999;140:2924-2927.
  35. Just RSJ, Furness SGB, ChristopoulosA, Sexton PM. Understanding Amylin Receptors. In: Hay DL, Dickerson IM, eds. The Calcitonin Gene-related Peptide Family Form, Function and Future Perspectives. Springer Dordrecht Heidelberg London New York; Springer; 2010:41-57.
  36. Nagae T, Mukoyama M, Sugawara A, Mori K, Yahata K, Kasahara M, Suganami T, Makino H, Fujinaga Y, Yoshioka T, Tanaka I, Nakao K. Rat receptor-activity-modifying proteins (RAMPs) for adrenomedullin/CGRP receptor: cloning and upregulation in obstructive nephropathy. Biochem Biophys Res Commun. 2000;270:89-93.
  37. Cottrell GS, Roosterman D, Marvizon JC, Song B, Wick E, Pikios S, Wong H, Berthelier C, Tang Y, Sternini C, Bunnett NW, Grady EF. Localization of calcitonin receptor-like receptor and receptor activity modifying protein 1 in enteric neurons, dorsal root ganglia, and the spinal cord of the rat. J Comp Neurol. 2005;490:239-255.
  38. Autelitano DJ, Ridings R. Adrenomedullin signalling in cardiomyocytes is dependent upon CRLR and RAMP2 expression. Peptides. 2001;22:1851-1857.
  39. Kamitani S, Asakawa M, Shimekake Y, Kuwasako K, Nakahara K, Sakata T. The RAMP2/CRLR complex is a functional adrenomedullin receptor in human endothelial and vascular smooth muscle cells. FEBS Lett. 1999;448:111-114.
  40. Evans BN, Rosenblatt MI, Mnayer LO, Oliver KR, Dickerson IM. CGRP-RCP, a novel protein required for signal transduction at calcitonin gene-related peptide and adrenomedullin receptors. J Biol Chem. 2000;275:31438-31443.
  41. Young A. Cardiovascular effects. Adv Pharmacol. 2005;52:239-250.
  42. Young AA, Crocker LB, Wolfe-Lopez D, Cooper GJ. Daily amylin replacement reverses hepatic glycogen depletion in insulin-treated streptozotocin diabetic rats. FEBS Lett. 1991;287:203-205.
  43. Young A, Kolterman O, Hall J. Amylin innocent in essential hypertension? Diabetologia. 1999;42:1029.
  44. Bell D, McDermott BJ. Activity of amylin at CGRP1-preferring receptors coupled to positive contractile response in rat ventricular cardiomyocytes. Regul Pept. 1995;60:125-133.
  45. Kaygisiz Z, Ozden H, Erkasap N, Koken T, Gunduz M, İkizler M, Kural T. Positive inotropic, positive chronotropic and coronary vasodilatory effects of rat amylin: mechanisms of amylin-induced positive inotropy. Acta Physiol Hung. 2010;97:362-374.
  46. Brain SD, Cambridge H. Calcitonin gene-related peptide: vasoactive effects and potential therapeutic role. Gen Pharmacol. 1996;27:607-611.
  47. Brain SD, Tippins JR, Morris HR, MacIntyre I, Williams TJ. Potent vasodilator activity of calcitonin gene-related peptide in human skin. J Invest Dermatol. 1986;87:533-536.
  48. Deng PY, Li YJ. Calcitonin gene-related peptide and hypertension. Peptides. 2005;26:1676-1685.
  49. Li Y, Zhang Y, Furuyama K, Yokoyama S, Takeda K, Shibahara S, Takahashi K. Identification of adipocyte differentiation-related regulatory element for adrenomedullin gene repression (ADRE-AR) in 3T3-L1 cells. Peptides. 2006;27:1405-1414.
  50. Ando K, Pegram BL, Frohlich ED. Hemodynamic effects of calcitonin gene-related peptide in spontaneously hypertensive rats. Am J Physiol. 1990;258:425-429.
  51. Gardiner SM, Compton AM, Kemp PA, Bennett T, Foulkes R, Hughes B. Regional haemodynamic effects of prolonged infusions of human alpha-calcitonin gene-related peptide in conscious, Long Evans rats. Br J Pharmacol. 1991;103:1509-1514.
  52. Wu D, Bassuk J, Adams JA. Calcitonin gene-related peptide protects against whole body ischemia in a porcine model of cardiopulmonary resuscitation. Resuscitation 2003;59:139-145.
  53. Champion HC, Bivalacqua TJ, Lambert DG, McNamara DB, Kadowitz PJ. The influence of candesartan and PD123319 on responses to angiotensin II in the hindquarters vascular bed of the rat. J Am Soc Nephrol. 1999;10(Suppl 11):95-97.
  54. Mulderry PK, Ghatei MA, Spokes RA, Jones PM, Pierson AM, Hamid QA, Kanse S, Amara SG, Burrin JM, Legon S. Differential expression of alpha-CGRP and beta-CGRP by primary sensory neurons and enteric autonomic neurons of the rat. Neuroscience. 1988;25:195-205.
  55. Tjen ALS, Ekman R, Lippton H, Cary J, Keith I. CGRP and somatostatin modulate chronic hypoxic pulmonary hypertension. Am J Physiol. 1992;263:681-690.
  56. Tam CW, Husmann K, Clark NC, Clark JE, Lazar Z, Ittner LM, Götz J, Douglas G, Grant AD, Sugden D, Poston L, Poston R, McFadzean I, Marber MS, Fischer JA, Born W, Brain SD. Enhanced vascular responses to adrenomedullin in mice overexpressing receptor-activity-modifying protein 2. Circ Res. 2006;98:262-270.
  57. Bell D, McDermott BJ. Calcitonin gene-related peptide in the cardiovascular system: characterization of receptor populations and their (patho)physiological significance. Pharmacol Rev. 1996;48:253-288.
  58. Marshall I. Mechanism of vascular relaxation by the calcitonin gene-related peptide. Ann N Y Acad Sci. 1992;657:204-215.
  59. Hirata Y, Takagi Y, Takata S, Fukuda Y, Yoshimi H, Fujita T. Calcitonin gene-related peptide receptor in cultured vascular smooth muscle and endothelial cells. Biochem Biophys Res Commun. 1988;151:1113-1121.
  60. Crossman DC, Dashwood MR, Brain SD, McEwan J, Pearson JD. Action of calcitonin gene-related peptide upon bovine vascular endothelial and smooth muscle cells grown in isolation and co-culture. Br J Pharmacol. 1990;99:71-76.
  61. Han SP, Naes L, Westfall TC. Calcitonin gene-related peptide is the endogenous mediator of nonadrenergic-noncholinergic vasodilation in rat mesentery. J Pharmacol Exp Ther. 1990;255:423-428.
  62. Edvinsson L. Calcitonin gene-related peptide (CGRP) and the pathophysiology of headache: therapeutic implications. CNS Drugs. 2001;15:745-753.
  63. Yoshimoto R, Mitsui-Saito M, Ozaki H, Karaki H. Effects of adrenomedullin and calcitonin gene-related peptide on contractions of the rat aorta and porcine coronary artery. Br J Pharmacol. 1998;123:1645-1654.
  64. Nelson MT, Huang Y, Brayden JE, Hescheler J, Standen NB. Arterial dilations in response to calcitonin gene-related peptide involve activation of K+ channels. Nature. 1990;344:770-773.
  65. Maggi CA. Tachykinins and calcitonin gene-related peptide (CGRP) as co-transmitters released from peripheral endings of sensory nerves. Prog Neurobiol. 1995;45:1-98.
  66. Wellman GC, Quayle JM, Standen NB. ATP-sensitive K+ channel activation by calcitonin gene-related peptide and protein kinase A in pig coronary arterial smooth muscle. J Physiol. 1998;507:117-129.
  67. Edvinsson L, Fredholm BB, Hamel E, Jansen I, Verrecchia C. Perivascular peptides relax cerebral arteries concomitant with stimulation of cyclic adenosine monophosphate accumulation or release of an endothelium-derived relaxing factor in the cat. Neurosci Lett. 1985;58:213-217.
  68. Strecker T, Dieterle A, Reeh PW, Weyand M, Messlinger K. Stimulated release of calcitonin gene-related peptide from the human right atrium in patients with and without diabetes mellitus. Peptides. 2006;27:3255-3260.
  69. Isaka M, Imamura M, Sakuma I, Makino Y, Shiiya N, Yasuda K. Cardiopulmonary bypass influences the plasma levels of calcitonin gene-related peptides in dogs: effects of hemofiltration and hemodilution. Res Vet Sci. 2007;82:110-114.
  70. Gray DW, Marshall I. Nitric oxide synthesis inhibitors attenuate calcitonin gene-related peptide endothelium-dependent vasorelaxation in rat aorta. Eur J Pharmacol. 1992;212:37-42.
  71. Meens MJ, Fazzi GE, van Zandvoort MA, De Mey JG. Calcitonin gene-related peptide selectively relaxes contractile responses to endothelin-1 in rat mesenteric resistance arteries. J Pharmacol Exp Ther. 2009;331:87-95.
  72. Feng CJ, Kang B, Kaye AD, Kadowitz PJ, Nossaman BD. L-NAME modulates responses to adrenomedullin in the hindquarters vascular bed of the rat. Life Sci. 1994;55:433-438.
  73. Miura K, Ebara T, Okumura M, Matsuura T, Kim S, Yukimura T, Iwao H. Attenuation of adrenomedullin-induced renal vasodilatation by NG-nitro L-arginine but not glibenclamide. Br J Pharmacol. 1995;115:917-924.
  74. Hirata Y, Hayakawa H, Suzuki Y, Suzuki E, Ikenouchi H, Kohmoto O, Kimura K, Kitamura K, Eto T, Kangawa K. Mechanisms of adrenomedullin-induced vasodilation in the rat kidney. Hypertension. 1995;25:790-795.
  75. He H, Bessho H, Fujisawa Y, Horiuchi K, Tomohiro A, Kita T, Aki Y, Kimura S, Tamaki T, Abe Y. Effects of a synthetic rat adrenomedullin on regional hemodynamics in rats. Eur J Pharmacol. 1995;273:209-214.
  76. Khan AI, Kato J, Kitamura K, Kangawa K, Eto T. Hypotensive effect of chronically infused adrenomedullin in conscious Wistar-Kyoto and spontaneously hypertensive rats. Clin Exp Pharmacol Physiol. 1997;24:139-142.
  77. Shimekake Y, Nagata K, Ohta S, Kambayashi Y, Teraoka H, Kitamura K, Eto T, Kangawa K, Matsuo H. Adrenomedullin stimulates two signal transduction pathways, cAMP accumulation and Ca2+ mobilization, in bovine aortic endothelial cells. J Biol Chem. 1995;270:4412-4417.
  78. Terata K, Miura H, Liu Y, Loberiza F, Gutterman DD. Human coronary arteriolar dilation to adrenomedullin: role of nitric oxide and K (+) channels. Am J Physiol Heart Circ Physiol. 2000;279:2620-2626.
  79. Hinson JP, Kapas S, Smith DM. Adrenomedullin, a multifunctional regulatory peptide. Endocr Rev. 2000;21:138-167.
  80. Gumusel B, Hao Q, Hyman AL, Kadowitz PJ, Champion HC, Chang JK, Mehta JL, Lippton H. Analysis of responses to adrenomedullin-(13-52) in the pulmonary vascular bed of rats. Am J Physiol. 1998;274:1255-1263.
  81. Parkes DG, May CN. Direct cardiac and vascular actions of adrenomedullin in conscious sheep. Br J Pharmacol. 1997;120:1179-1185.
  82. Stangl D, Muff R, Schmolck C, Fischer JA. Photoaffinity labeling of rat calcitonin gene-related peptide receptors and adenylate cyclase activation: identification of receptor subtypes. Endocrinology. 1993;132:744-750.
  83. Majid DS, Kadowitz PJ, Coy DH, Navar LG. Renal responses to intra-arterial administration of adrenomedullin in dogs. Am J Physiol. 1996;270:200-205.
  84. Nossaman BD, Feng CJ, Kaye AD, Dewitt B, Coy DH, Murphy WA, Kadowitz PJ. Pulmonary vasodilator responses to adrenomedullin are reduced by NOS inhibitors in rats but not in cats. Am J Physiol. 1996;270:782-789.
  85. Champion HC, Lambert DG, McWilliams SM, Shah MK, Murphy WA, Coy DH, Kadowitz PJ. Comparison of responses to rat and human adrenomedullin in the hindlimb vascular bed of the cat. Regul Pept. 1997;70:161-165.
  86. Champion HC, Wang R, Shenassa BB, Murphy WA , Coy DH, Hellstrom WJ, Kadowitz PJ. Adrenomedullin induces penile erection in the cat. Eur J Pharmacol. 1997;319:71-75.
  87. Champion HC, Wang R, Santiago JA, Murphy WA , Coy DH, Kadowitz PJ, Hellstrom WJ. Comparison of responses to adrenomedullin and calcitonin gene-related peptide in the feline erection model. J Androl. 1997;18:513-521.
  88. Lang MG, Paterno R, Faraci FM, Heistad DD. Mechanisms of adrenomedullin-induced dilatation of cerebral arterioles. Stroke. 1997;28:181-185.
  89. Sabates BL, Pigott JD, Choe EU, Cruz MP, Lippton HL, Hyman AL, Flint LM, Ferrara JJ. Adrenomedullin mediates coronary vasodilation through adenosine receptors and KATP channels. J Surg Res. 1997;67:163-168.
  90. Brain SD, Poyner DR, Hill RG. CGRP receptors: a headache to study, but will antagonists prove therapeutic in migraine? Trends Pharmacol Sci. 2002;23:51-53.
  91. Dewachter L, Dewachter C, Naeije R. New therapies for pulmonary arterial hypertension: an update on current bench to bedside translation. Expert Opin Investig Drugs 2010;19:469-488.
  92. Zhao L, Brown LA, Owji AA, Nunez DJ, Smith DM, Ghatei MA, Bloom SR, Wilkins MR. Adrenomedullin activity in chronically hypoxic rat lungs. Am J Physiol. 1996;271:622-629.
  93. Nagaya N, Nishikimi T, Uematsu M, Satoh T, Oya H, Kyotani S, Sakamaki F, Ueno K, Nakanishi N, Miyatake K, Kangawa K. Haemodynamic and hormonal effects of adrenomedullin in patients with pulmonary hypertension. Heart. 2000;84:653-658.
  94. Vizza CD, Letizia C, Sciomer S, Naeije R, Rocca GD, Roma AD, Musaro S, Quattrucci S, Gaudio C, Battagliese A, Badagliacca R, Erasmo ED, Fedele F. Increased plasma levels of adrenomedullin, a vasoactive peptide, in patients with end-stage pulmonary disease. Regul Pept. 2005;124:187-193.
  95. Kakishita M, Nishikimi T, Okano Y, Satoh T, Kyotani S, Nagaya N, Fukushima K, Nakanishi N, Takishita S, Miyata A, Kangawa K, Matsuo H, Kuniea T. Increased plasma levels of adrenomedullin in patients with pulmonary hypertension. Clin Sci (Lond). 1999;96:33-39.
  96. Nagaya N, Kyotani S, Uematsu M, et Ueno K, Oya H, Nakanishi N, Shirai M, Mori H, Miyateke K, Kangawa K. Effects of adrenomedullin inhalation on hemodynamics and exercise capacity in patients with idiopathic pulmonary arterial hypertension. Circulation. 2004;109:351-356.
  97. Takei Y, Joss JMP, Kloas W, Rankin JC. Identification of angiotensin I in several vertebrate species: its structural and functional evolution. Gen Comp Endocrinol. 2004;135:286-292.
  98. Dong F, Taylor MM, Samson WK, Ren J. Intermedin (adrenomedullin-2) enhances cardiac contractile function via a protein kinase C- and protein kinase A-dependent pathway in murine ventricular myocytes. J Appl Physiol. 1985;2006;101:778-784.
  99. Yang JH, Jia YX, Pan CS, Zhao J, Ouyang M, Yang J, Chang JK, Tang CS, Qİ YF. Effects of intermedin (1-53) on cardiac function and ischemia/reperfusion injury in isolated rat hearts. Biochem Biophys Res Commun. 2005;327:713-719.
  100. Yang JH, Cai Y, Duan XH, Ma CG, Wang X, Tang CS, Qİ YF. Intermedin 1-53 inhibits rat cardiac fibroblast activation induced by angiotensin II. Regul Pept. 2009;158:19-25.
  101. Song JQ, Teng X, Cai Y, Tang CS, Qi YF. Activation of Akt/GSK-3beta signaling pathway is involved in intermedin (1-53) protection against myocardial apoptosis induced by ischemia/reperfusion. Apoptosis. 2009;14:1061-1069.
  102. Fujisawa Y, Nagai Y, Miyatake A, Miura K, Nishiyama A, Kimura S, Abe Y. Effects of adrenomedullin 2 on regional hemodynamics in conscious rats. Eur J Pharmacol. 2007;558:128-132.
  103. Burak Kandilci H, Gumusel B, Wasserman A, Witriol N, Lippton H. Intermedin/adrenomedullin-2 dilates the rat pulmonary vascular bed: dependence on CGRP receptors and nitric oxide release. Peptides. 2006;27:1390-1396.
  104. Fujisawa Y, Nagai Y, Miyatake A, Takei Y, Miura K, Shoukouji T, Nishiyama A, Kimura S, Abe Y. Renal effects of a new member of adrenomedullin family, adrenomedullin2, in rats. Eur J Pharmacol. 2004;497:75-80.
  105. Jolly L, March JE, Kemp PA, Bennett T, Gardiner SM. Mechanisms involved in the regional haemodynamic effects of intermedin (adrenomedullin 2) compared with adrenomedullin in conscious rats. Br J Pharmacol. 2009;157:1502-1513.
  106. Telli G, Erac Y, Tel BC, Gumusel B. Mechanism of adrenomedullin 2/intermedin mediated vasorelaxation in rat main pulmonary artery. Peptides. 2018;103:65-71.
  107. Grossini E, Molinari C, Mary DA, Uberti F, Caimmi PP, Vacca G. Intracoronary intermedin 1-47 augments cardiac perfusion and function in anesthetized pigs: role of calcitonin receptors and beta-adrenoreceptor-mediated nitric oxide release. J Appl Physiol (1985) 2009;107:1037-1050.
  108. Pfeil U, Aslam M, Paddenberg R, Quanz K, Chang CL, Park JII, Gries B, Rafiq A, Faulhammer P, Goldenberg A, Papadakis T, Noll T, Hsu SYT, Weissmann N, Kummer W . Intermedin/adrenomedullin-2 is a hypoxia-induced endothelial peptide that stabilizes pulmonary microvascular permeability. Am J Physiol Lung Cell Mol Physiol. 2009;297:837-845.
  109. Kandilci HB, Gumusel B, Lippton H. Intermedin/adrenomedullin-2 (IMD/AM2) relaxes rat main pulmonary arterial rings via cGMP-dependent pathway: role of nitric oxide and large conductance calcium-activated potassium channels (BK(Ca)). Peptides. 2008;29:1321-1328.
  110. Chen L, Kis B, Hashimoto H, Busija DW, Takei Y, Yamashita H, Ueta Y. Adrenomedullin 2 protects rat cerebral endothelial cells from oxidative damage in vitro. Brain Res. 2006;1086:42-49.
  111. Mao SZ, Fan XF, Xue F, Chen R, Ying Chen XY, Yuan GS, Gang Hu L, Liu SF, Gong YS. Intermedin modulates hypoxic pulmonary vascular remodeling by inhibiting pulmonary artery smooth muscle cell proliferation. Pulm Pharmacol Ther. 2014;27:1-9.
  112. Chen H, Wang X, Tong M, Wu D, Wu S, Chen J, Wang X, Wang X, Kang Y, Tang H, Tang C, Jiang W. Intermedin suppresses pressure overload cardiac hypertrophy through activation of autophagy. PLoS One. 2013;8:64757.
  113. Li P, Sun HJ, Han Y, Wang JJ, Zhang F, Tang CS, Zhou YB. Intermedin enhances sympathetic outflow via receptor-mediated cAMP/PKA signaling pathway in nucleus tractus solitarii of rats. Peptides. 2013;47:1-6.
  114. Chang CL, Roh J, Hsu SYT. Intermedin, a novel calcitonin family peptide that exists in teleosts as well as in mammals: a comparison with other calcitonin/intermedin family peptides in vertebrates. Peptides. 2004;25:1633-1642.
  115. Gong YS, Fan XF, Wu XM, Hu LG, Tang CS, Pang YZ, Qİ YF. [Changes of intermedin/adrenomedullin 2 and its receptors in the right ventricle of rats with chronic hypoxic pulmonary hypertension]. Sheng Li Xue Bao. 2007;59:210-214.
  116. Gong YS, Zhang L, Guo YM, Gang Hu L, Mao SZ, Fang XF, Huang P, Hong L. [Effect of hypoxia on the expressions of intermedin/ adrenomedullin2 in plasma and the tissues of heart and lung in rats]. Zhongguo Ying Yong Sheng Li Xue Za Zhi. 2009;25:8-11.
  117. Fan XF, Huang P, Gong YS, Wu XM, Hu LG, Tian LX, Tang CS, Pang YZ. [Changes of adrenomedullin 2/intermedin in the lung of rats with chronic hypoxic pulmonary hypertension]. Zhongguo Ying Yong Sheng Li Xue Za Zhi. 2007;23:467-471.
  118. Ni XQ, Zhang JS, Tang CS, Qi YF. Intermedin/adrenomedullin2: an autocrine/paracrine factor in vascular homeostasis and disease. Sci China Life Sci. 2014;57:781-789.
  119. Telli G, Tel BC, Yersal N, Korkusuz P, Gumusel B. Effect of intermedin/adrenomedullin2 on the pulmonary vascular bed in hypoxia-induced pulmonary hypertensive rats. Life Sci. 2018;192:62-67.
  120. Telli G, Kandilci HB, Tel BC, Gümüşel B. Intermedin/Adrenomedullin 2 (IMD/AM2) is a potent vasodilator in chronic hypoxia induced pulmonary hypertensive isolated rat lungs. Faseb Journal 2016;30(Suppl 1).