Vasorelaxation effect of Glycyrrhizae uralensis through the endothelium-dependent Pathway.
BACKGROUND
Glycyrrhiza uralensis (G. uralensis) is one of the herbs used in traditional Chinese medicine (TCM) and serves as an envoy medicinal. Since G. uralensis plays a major role in the anti-hypertensive TCM formulae, we believe that G. uralensis might possess vasorelaxation activity.


OBJECTIVE
This study is designed to investigate the vasorelaxation effect of G. uralensis from various extracts and to study its pharmacology effect.


METHODS
The vasorelaxation effect of G. uralensis extracts were evaluated on thoracic aortic rings isolated from Sprague Dawley rats.


RESULTS
Among these three extracts of G. uralensis, 50% ethanolic extract (EFG) showed the strongest vasorelaxation activity. EFG caused the relaxation of the aortic rings pre-contracted with phenylephrine either in the presence or absence of endothelium and pre-contracted with potassium chloride in endothelium-intact aortic ring. Nω-nitro-L-arginine methyl ester, methylene blue, or 1H-[1,2,4]Oxadiazolo[4,3-a]quinoxalin-1-one inhibit the vasorelaxation effect of EFG in the presence of endothelium. On the other hand, in the presence of the potassium channel blockers (tetraethylammonium and barium chloride), the vasorelaxation effect of EFG was not affected, but glibenclamide and 4-aminopyridine did inhibit the vasorelaxation effect of EFG. With indomethacin, atropine and propranolol, the vasorelaxation effect by EFG was significantly reduced. EFG was also found to be effective in reducing Ca2+release from sarcoplasmic reticulum and the blocking of calcium channels.


CONCLUSIONS
The results obtained suggest that EFG is involved in the NO/sGC/cGMP pathway.
School of Pharmaceutical Sciences, Universiti Sains Malaysia, USM 11800 Minden, Pulau Pinang, Malaysia.
Chu Shan
CS
Tan
School of Pharmaceutical Sciences, Universiti Sains Malaysia, USM 11800 Minden, Pulau Pinang, Malaysia.
Yung Sing
YS
Ch'ng
School of Pharmaceutical Sciences, Universiti Sains Malaysia, USM 11800 Minden, Pulau Pinang, Malaysia.
Yean Chun
YC
Loh
School of Pharmaceutical Sciences, Universiti Sains Malaysia, USM 11800 Minden, Pulau Pinang, Malaysia.
Mohd
M
Zaini Asmawi
School of Pharmaceutical Sciences, Universiti Sains Malaysia, USM 11800 Minden, Pulau Pinang, Malaysia.
Mariam
M
Ahmad
School of Pharmaceutical Sciences, Universiti Sains Malaysia, USM 11800 Minden, Pulau Pinang, Malaysia. Electronic address: yammunfei@yahoo.com.
Mun Fei
MF
Yam
D000818:Animals; D001013:Aorta, Thoracic / Q000187:drug effects / Q000502:physiology; D004305:Dose-Response Relationship, Drug; D004730:Endothelium, Vascular / Q000187:drug effects* / Q000502:physiology; D029882:Glycyrrhiza uralensis; D008297:Male; D009924:Organ Culture Techniques; D010936:Plant Extracts / Q000302:isolation & purification / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D014664:Vasodilation / Q000187:drug effects* / Q000502:physiology
D010936:Plant Extracts
Ca(2+) channels; Glycyrrhizae uralensis; K(+) channels; NO/sGC/cGMP pathway; Vasorelaxation