The Role of K+ Channel Subtypes in Catechin Induced Vasorelaxation in Rat’s Aortic Rings.

  • Omar A. M. Al-Habib University of Zakho
  • Fakhir N. K. Sabir Koya University
Keywords: K channel blockers, Catechin, vasorelaxation, aorta


The current study aimed to investigate the role of K+ channels subtypes in relaxant effects of catechin on rat’s aortic rings. The isometric tension of the thoracic aorta was measured using ADI PowerLab Data Acquisition System.  Catechin at concentrations (10-5 to 5x10-1M) produced more potent relaxant effects in phenylephrine (10-6 M)  precontracted aortic smooth muscle  with Log IC50’s of -1.159 mg/ml as compared to potassium chloride (60 mM) with Log IC50’s of -6.373  mg/ml . The catechin induced relaxation in aortic rings precontracted with phenylephrine was 17.464 ± 0.068 %, where as for  aortic rings precontracted with potassium was only 5.574 ± 0.131%.  In aortic rings preincubated with glibenclamide (10-5M) and tetraethylammonium (1mM), catechin  relaxant effect was enhanced with Log IC50s of -3.119 and -3.001 mg/ml, respectively. On the other hand, in aortic rings precontracted with PE and preincubated with BaCland 4-AP, catechin induced    statistically non-significant relaxant effects as compared with aortic rings of the control aortic ring  which was precontracted with PE. From the results of the current study, it can be concluded that catechin produced more potent vasorelaxant effect on aortic rings preincubated with phenylephrine that KCl. This vasorelaxant effect of catechin is produced via the activation of  both KATP and Kca, but not Kir and Kv channels subtypes.

Author Biographies

Omar A. M. Al-Habib, University of Zakho

Dept. of Biology, Faculty of Science, University of Zakho, Kurdistan Region - Iraq.

Fakhir N. K. Sabir, Koya University

Dept. of Biology, Faculty of Science and Health, Koya University, Kurdistan Region – Iraq.


Alessio, H. M., Hagerman, A. E., Romanello, M., Carando, S., Threlkeld,
A. E., Rogers, M. S., Dimitrova, Y., Muhammed, S. and Wiley, R. L. (2003) Consumption of green tea protects rats from exercise-induced oxidative stress in kidney and liver. Nutr. Res. 22: 1177–1188.
Alvarez, E.; Campos-Toimil, M.; Justiniano-Basaran, H.; Lugnier, C. and Orallo, F. (2006). Study of the mechanisms involved in the vasorelaxation induced by (-)-epigallocatechin- 3-gallate in rat aorta. Br. J. Pharmacol. 147: 269-280.
Alvarez-Castro, E.; Campos-Toimil, M. and Orallo, F.( 2004). Epigallocatechin-3- gallate induces contraction of the rat aorta by a calcium influx-dependent mechanism. Naunyn-Schmiedeberg's Arch. Pharmacol. 369: 496-506.
Crespy, V. and Williamson, G. (2004): A Review of the Health Effects of Green Tea Catechins in In Vivo Animal Models. J. Nutr. 134: 3431S–3440S.
Dulloo, A. G. ; Duret, C. ; Rohrer, D. ; Girardier, L. ; Mensi, N. ; Fathi, M. ; Chantre, P. and Vandermander, J. (1999). Efficacy of a green tea extract rich in catechin polyphenols and caffeine in increasing 24-h energy expenditure and fat oxidation in humans. Am. J. Clin. Nutr. 70:1040–1045.
Fulton, D.; McGiff, J. and Quilley J. (1996). Role of phospholipase C and phospholipase A2 in the nitric oxide-independent vasodilator effect of bradykinin in the rat perfused heart. J. Pharmacol. Exp. Ther. 278: 518-526.
Ghayur, M. N.; Khan, H. and Gilani , A. H. (2007). Antispasmodic, Bronchodilator and vasodilator activities of (+)-catechin, a naturally occurring flavonoid. Arch. Pharm. Res. 30 (8): 970-975.
Huang, Y. ; Chan, N. W.; Lau, C. W. ; Yao, X. Q. ; Chan, F. L. and Chen, Z. Y. (1999). Involvement of endothelium/nitric oxide in vasorelaxation induced by purified green tea (−) - epicatechin. Biochim. Biophys. Acta. 1427: 322-328.
Huang, Y.; Zhang, A.; Lau, C. W. and Chen, Z. Y. (1998). Vasorelaxant effects of purified green tea epicatechin derivatives in rat mesenteric artery. Life Sci. 63: 275-283.
Kubo, M.; Nakaya, Y.; Matsuoka, S.; Saito, K. and Kuroda, Y. (1993) . Atrial natriuretic factor and isosorbide dinitrate modulate the gating of ATP sensitive K+ channels in cultured vascular smooth muscle. Circ. Res. 74:471 -476.
Lorenz, M. ; Wessler, S. ; Follman , E. ; Michaelis ,W. ; Dusterhoft , T. ; Baumann, G. ; Stangl , K. and Stangl, V. (2004). A constituent of green tea, epigallocatechin-3-gallate, activates endothelial nitric oxide synthase by phosphatidylinositol-3-OH-kinase, cAMPdependent protein kinase, and Aktdependent pathway and leads to endothelial-dependent vasorelaxation. J. Biol. Chem. 279: 6190-6195.
Mizugaki, M.; Ishizawa, F.; Yamazaki, T. and Hishinuma, T. (2000). Epigallocatechin gallate increase the prostacyclin production of bovine aortic endothelial cells. Prostaglandins Other Lipid Mediat. 62: 157-164.
Pechanova, Z. W. (2002). Effects of red wine polyphenolic compounds on the cardiovascular System. Bratisl. Lek. Listy. 103 (4-5): 159 - 165.
Sanae, F.; Miyaichi, Y.; Kizu, H. and Hayashi, H. (2002). Effects of catechins on vascular tone in rat thoracic aorta with endothelium. Life Sciences 71(21): 2553-2562.
Shekha, M. S. and Al-Habib, O. A. ( 2012): Vasorelaxant, antispasmodic and cardiotonic effect of the chloroform fraction of Crataegus aronia on isolated rat muscles. Int. Jour. Biol. And Biomed Sci. 1 (1): 06-11.
Shekha, M. S. (2010). Physiological Effects of Crataegus aronia Fractions on isolated Smoothmuscles and Perfused “Langendorff” Heart in Albino rats. Ph.D. thesis, University of Duhok. Duhok. Iraq.
Shen, J. -Z.; Zheng, X. -F.; Wei, Er-O. and Kwan, C.-Y. (2003). Green tea catechins evoke a phasic contraction in rat aorta via H2O2- mediated multiple signalling pathways. Clin. Exper. Pharmac. Physiol. 30(1-2):88–95.
Tijburg, L. B., Wiseman, S. A., Meijer, G. W. and Weststrate, J. A. (1997)
Effects of green tea, black tea and dietary lipophilic antioxidants on LDL oxidizability and atherosclerosis in hypercholesterolaemic rabbits. Atherosclerosis 135: 37–47.
Williamson G and Manach C. ( 2005): Bioavailability and bioefficacy of polyphenols in humans. II. Review of 93 intervention studies. Am J Clin Nutr; 81:243S-255S.

Yang, J. A., Choi, J. H. & Rhee, S. J. (1999) Effects of green tea catechin on phospholipase A2 activity and antithrombus in streptozotocin diabetic rats. J. Nutr. Sci. Vitaminol. 45: 337–346.
How to Cite
Al-Habib, O., & Sabir, F. (2015). The Role of K+ Channel Subtypes in Catechin Induced Vasorelaxation in Rat’s Aortic Rings. Science Journal of University of Zakho, 3(1), 1-8. Retrieved from
Science Journal of University of Zakho