The Role of Endothelium and Endothelium-Derived Relaxation Factors in Nitric Oxide-Induced Aortic Relaxation

  • ABBAS B. QADIR SALIHI University of Salahaddin
  • OMAR A.M. AL-HABIB University of Zakho
Keywords: Nitric Oxide, Endothelium denudation, Endothelium derived-relaxation factors, Organ bath, PowerLab system, Aorta


The endothelium plays a key role in the control of vascular patency and tone. Thus, the main objective of the study was to determine the role of endothelium and its derived relaxation factors in mediating relaxation of rat thoracic aorta, in response to nitric oxide (NO) donor “sodium nitroprusside (SNP)” using PowerLab tissue bath system. Endothelial denudation enhanced relaxation responses of SNP(1X10-8 to 3X10-5 M)with IC50 of5.872X10-8 as compared to control rings with IC50’s of 2.266X10-6M, as well as the maximum relaxation (Emax) for both groups were 106.2±4.95% and 83.13±14.755%, respectively. The relaxation responses to SNP in aortic rings were significantly increased by Indomethacin and Clotrimazole pretreatment with IC50’s of 1.72X10-7 M and 3.314 X10-8M, and Emax were increased to 121.5±5% and 121.1±8.09%, respectively. Whilst, no changes were observed in aortic rings pretreated with L-nitroargininemethylester (L-NAME) and methylene blue. The results of the current study had shown that endothelium denudation and blocking of endothelium derived-relaxation factors enhanced vasodilator effect of NO; this may be account for the role of endothelium in the vasodilatory effects of NO.

Author Biographies

ABBAS B. QADIR SALIHI, University of Salahaddin

Biology Dept., College of Science, University of Salahaddin, Erbil, Kurdistan, Iraq.

OMAR A.M. AL-HABIB, University of Zakho

Biology Dept., Faculty of Science, University of Zakho, Duhok, Kurdistan, Iraq.


Adams, D J and Hill M A. 2004. Potassium channels and membrane potential in the modulation of intracellular calcium in vascular endothelial cells. J CardiovascElectrophysiol. 15(5):598-610.
Aziz, N; Malik H; Safur R; Samra B; Sidra R and Anwar H. 2009.Antihypertensive, antioxidant, antidyslipidemic and endothelial modulating activities of a polyherbal formulation (POL-10).Vascular Pharmacology. 50:57–64.
Dong, H; Gareth J; Denise G; William C and Christopher R. 1997.NO/PGI2-independent vasorelaxation and the cytochrome P450 pathway in rabbit carotid artery.Brit J Phar. 120, 695-701.
Hampl, V and Herget J. 2000.Role of nitric oxide in the pathogenesis of chronic pulmonary hypertension.Physiol. Rev. 80: 1337–1372.
Ignarro, L. 2010. Nitric oxide: Biology and pathobiology. Elsevier Inc.
Khatsenko, O; Gross O; Rifkind A and Vane J. 1993. Nitric oxide is a mediator of the decrease in cytochrome P450-dependent metabolism caused by immunostimulants. ProcNatlAcadSci U S A. 90 (23): 11147.
Lugo, B; Hernández D; Castillo C and Hong E. 1998. Prostaglandin and nitric oxide interactions in rat aorta. Proc West Pharmacol Soc. 41:91-2.
Luscher, T and Barton M. 1997.Biology of the endothelium.ClinCardiol. 20(II):3-10.
MacDonald, P;Kudo K; Dubbin P and Dusting G.1989. Rat aortic endothelium antagonizes nitroprusside-induced relaxation by release of the peptide endothelin. ClinExpPharmacol Physiol. 16(4):223-7.
Motulsky, H and Christopolous A. 2003.GrdaphPad Prism: Fitting models to biological data using linear and non-linear regression; A practical guide to curve fitting. GraphPad software, Inc.
Panza, J. 1997. Endothelial dysfunction in essential hypertension. ClinCardiol. 20(11 Suppl 2):II-26-33.
Shelkovnikov, S; Craig A and Harvey C. 2004. Influence of nitric oxide donors and peroxynitrite on the contractile effect and concentration of norepinephrine. Life Sciences.74; 2919–2928.
Si, J; Hui Z ; Yuqin Y; Zhi-Gen J and Alfred L. 2002. Nitric oxide induces hyperpolarization by opening ATP-sensitive K‏ channels in guinea pig spiral modiolar artery. Hearing Research. 171;167-176.
Ying, W and Sanders P. 2002. Increased dietary salt activates rat aortic endothelium. Hypertension. 39(2):239-44.
Zhang, D. 2007. Hydroperoxide-induced Oxidative Stress in the Arterial Wall: Pharmacological Characterization of the Effects on Arterial Contractility. Academic thesis: EberhardKarlsUniversitätTübingen
How to Cite
QADIR SALIHI, A., & AL-HABIB, O. (2013). The Role of Endothelium and Endothelium-Derived Relaxation Factors in Nitric Oxide-Induced Aortic Relaxation. Science Journal of University of Zakho, 1(1), 95-100. Retrieved from
Science Journal of University of Zakho