Pharmacological mechanisms underlying the vascular activities of Loranthus ferrugineus Roxb. in rat thoracic aorta
2010
Ameer, Omar Z. | Salman, Ibrahim M. | Siddiqui, Mohammad Jamshed A. | Yam, Mun F. | Sriramaneni, Raghava N. | Mohamed, Ali J. | Sadikun, Amirin | Ismail, Zhari | Shah, Amin M. | Asmawi, Mohd. Z.
Aim of the study: The present study was aimed to investigate the pharmacological basis for the use of Loranthus ferrugineus in hypertension. Materials and methods: Loranthus ferrugineus methanol extract (LFME) was obtained using Soxhelt extractor and then successively fractionated using chloroform, ethyl acetate and n-butanol. The n-butanol fraction of LFME (NBF-LFME) was studied using isolated rat thoracic aorta. Results: NBF-LFME (1.0×10⁻⁵ to 3.0mg/ml) was found to be the most potent to concentration-dependently relax the endothelium-intact phenyephrine (PE, 1μM)- and high K⁺ (80mM)-precontracted rat aortic rings. Removal of the endothelium completely abolished the vascular relaxing properties of NBF-LFME. Pretreatment with atropine (1μM), l-NAME (10μM), indomethacin (10μM) and methylene blue (10μM) significantly blocked NBF-LFME-mediated relaxation. Endothelium-dependent and -independent relaxations induced by acetylcholine (ACh) and sodium nitroprusside (SNP), respectively, were significantly enhanced in aortic rings pretreated with NBF-LFME when compared to those observed in control aortic rings. On the contrary, glibenclamide (10μM), propranolol (1μM) and prazosin (0.01μM) did not alter NBF-LFME-induced relaxation. Conclusions: The results suggest that NBF-LFME induced vascular relaxation by stimulating muscarinic receptors, activating the endothelium-derived nitric oxide-cGMP-relaxant pathway, promoting prostacyclin release and/or possibly through its ability to lengthen the released nitric oxide half-life. The present data further supports previous in vivo findings and explain the traditional use of Loranthus ferrugineus as an anti-hypertensive agent.
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