Pharmacological mechanisms underlying the vascular activities of Loranthus ferrugineus Roxb. in rat thoracic aorta.
OBJECTIVE
The present study was aimed to investigate the pharmacological basis for the use of Loranthus ferrugineus in hypertension.


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 x 10(-5) to 3.0mg/ml) was found to be the most potent to concentration-dependently relax the endothelium-intact phenyephrine (PE, 1 microM)- and high K(+) (80 mM)-precontracted rat aortic rings. Removal of the endothelium completely abolished the vascular relaxing properties of NBF-LFME. Pretreatment with atropine (1 microM), L-NAME (10 microM), indomethacin (10 microM) and methylene blue (10 microM) 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 (10 microM), propranolol (1 microM) and prazosin (0.01 microM) 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.
Ameer
Omar Z
OZ
Department of Physiology & Pharmacology, School of Pharmaceutical Sciences, Universiti Sains Malaysia, Minden, 11800 Penang, Malaysia. omar_3m@yahoo.com
Salman
Ibrahim M
IM
Siddiqui
Mohammad Jamshed A
MJ
Yam
Mun F
MF
Sriramaneni
Raghava N
RN
Mohamed
Ali J
AJ
Sadikun
Amirin
A
Ismail
Zhari
Z
Shah
Amin M
AM
Asmawi
Mohd Z
MZ
D000818:Animals; D000959:Antihypertensive Agents / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000493:pharmacokinetics / Q000494:pharmacology*; D000975:Antioxidants / Q000032:analysis; D001013:Aorta, Thoracic / Q000187:drug effects*; D004305:Dose-Response Relationship, Drug; D004357:Drug Synergism; D004730:Endothelium, Vascular / Q000187:drug effects / Q000502:physiology; D005419:Flavonoids / Q000032:analysis; D066298:In Vitro Techniques; D028183:Loranthaceae / Q000737:chemistry*; D008296:Malaysia; D008297:Male; D008518:Medicine, East Asian Traditional; D010636:Phenols / Q000032:analysis; D008517:Phytotherapy; D035261:Plant Components, Aerial / Q000737:chemistry; D010936:Plant Extracts / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000493:pharmacokinetics / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D014662:Vasoconstrictor Agents / Q000037:antagonists & inhibitors / Q000494:pharmacology; D014664:Vasodilation / Q000187:drug effects; D014665:Vasodilator Agents / Q000493:pharmacokinetics / Q000494:pharmacology
D000959:Antihypertensive Agents; D000975:Antioxidants; D005419:Flavonoids; D010636:Phenols; D010936:Plant Extracts; D014662:Vasoconstrictor Agents; D014665:Vasodilator Agents