title: Endothelium-dependent relaxation induced by hawthorn extract in rat mesenteric artery.
abstract: The extract prepared from hawthorn (Crataegus fruit) was examined for its relaxant effect in rat isolated mesenteric arteries. Hawthorn extract induced concentration-dependent relaxation of the U46619-precontracted artery with an IC50 of 0.22 +/- 0.02 mg/ml. Removal of the functional endothelium reduced by approximately 85% the maximum relaxant response to hawthorn extract. Pretreatment of the arterial tissues with N(G)-nitro-L-arginine methyl ester (3-10 microM) or methylene blue (3-10 microM) inhibited the relaxation induced by hawthorn extract, while indomethacin (10 microM) had no effect. L-arginine (3 mM) did not affect the relaxation induced by hawthorn extract but partially reversed the effect of 10 microM N(G)-nitro-L-arginine methyl ester. Iberiotoxin (100 nM) slightly but significantly inhibited the relaxant effect of hawthorn extract whilst glibenclamide (3 microM) was ineffective. Glibenclamide at 3 microM reversed the relaxation induced by pinacidil. N(G)-nitro-L-arginine methyl ester and methylene blue markedly inhibited acetylcholine-induced relaxation in endothelium-intact arteries. Hawthorn extract also reduced the contraction induced by phenylephrine (1 microM) or high Ki (60 mM) with respective IC50 values of 0.13 +/- 0.01 mg/ml and 0.11 +/- 0.01 mg/ml. In high K+-contracted arteries, hawthorn extract induced only 55% of relaxation while it caused a complete inhibition of the U46619- or phenylephrine-induced contraction. These results suggest that hawthorn contains active components which cause vasorelaxation in rat isolated mesenteric arteries. Nitric oxide but not other endothelium-derived vasoactive factors was probably involved in the relaxation induced by hawthorn extract.
authors.affiliation: Food and Nutritional Science Program of Department of Biochemistry, Chinese University of Hong Kong, Shatin.
authors.forename: Z Y
authors.initials: ZY
authors.lastname: Chen
authors.forename: Z S
authors.initials: ZS
authors.lastname: Zhang
authors.forename: K Y
authors.initials: KY
authors.lastname: Kwan
authors.forename: M
authors.initials: M
authors.lastname: Zhu
authors.forename: W K
authors.initials: WK
authors.lastname: Ho
authors.forename: Y
authors.initials: Y
authors.lastname: Huang
mesh_terms: D000818:Animals; D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000494:pharmacology; D004730:Endothelium, Vascular / Q000187:drug effects* / Q000502:physiology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D066298:In Vitro Techniques; D007213:Indomethacin / Q000494:pharmacology; D008297:Male; D008638:Mesenteric Arteries / Q000187:drug effects*; D008751:Methylene Blue / Q000494:pharmacology; D009126:Muscle Relaxation / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000187:drug effects*; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors; D010936:Plant Extracts / Q000494:pharmacology; D011188:Potassium / Q000494:pharmacology; D026902:Potassium Channel Blockers; D051381:Rats; D017207:Rats, Sprague-Dawley; D019685:Rosales / Q000737:chemistry*
chemical_list: D000894:Anti-Inflammatory Agents, Non-Steroidal; D004791:Enzyme Inhibitors; D010936:Plant Extracts; D026902:Potassium Channel Blockers; D019001:Nitric Oxide Synthase; D011188:Potassium; D008751:Methylene Blue; D019331:NG-Nitroarginine Methyl Ester; D007213:Indomethacin